Narodna in univerzitetna knjižnica v LJubljani ISSN 0016-7789 1996 Ljubljana 1997 GEOLOGIJA GEOLOGIJA LETNIK 1996 KNJIGA 39 Str. 1 do 311 GEOLOGIJA Slovenska besedila za 39. knjigo je lektoriral Milan Pritekel]. V drugih jezikih napisani članki niso lektorirani in zanje odgovarjajo avtorji sami. Prevode v angleški jezik so opravili Simon Pire in delno sami avtorji. Za strokovno vsebino vseh člankov so avtorji odgovorni sami Izdajatelja: Geološki zavod Ljubljana in Slovensko geološko društvo Glavni in odgovorni urednik: Editor-in-Chief: Stanko Buser, Ljubljana, Slovenija Uredniški odbor: Editorial Board: Stanko Buser, Ljubljana, Slovenia; Matija Drovenik, Ljubljana, Slovenia; Endre Dudich, Budapest, Hungary; Erik Flügel, Erlangen, Germany; Miklós Kedves, Szeged, Hungary; Harald Lobitzer, Wien, Austria; German Müller, Heidelberg, Germany; Rinaldo Nicolich, '&ieste, Italy; Bojan Ogorelec, Ljubljana, Slovenia; Simon Pire, Ljubljana, Slovenia; Danilo Ravnik, Ljubljana, Slovenia; Mihael Ribičič, Ljubljana, Slovenia; Marko Šparica, Zagreb, Croatia; Dra- gica Turnšek, Ljubljana, Slovenia; Miran Veselič, Ljubljana, Slovenia Naslov: Address: GEOLOGIJA, Geološki zavod Ljubljana, Inštitut za geologijo, geotehniko in geofiziko, Dimičeva 14, 1000 Ljubljana, Slovenija Naklada 600 izvodov Cena 4000 SIT Tisk in vezava: Delo-Tiskarna d.d., Ljubljana, Dunajska 5, leto 1997 Financirata: Ministrstvo za znanost in tehnologijo Republike Slovenije in Geološki zavod Ljubljana, Inštitut za geologijo, geotehniko in geofiziko Po mnenju Urada Vlade za informiranje Republike Slovenije št. 23/109-93, z dne 14. aprila 1993 je ta publikacija uvrščena med proizvode, za katere se plačuje 5-odstotni davek od prometa GEOLOGIJA The papers in Slovene language of the present 39 volume were edited by Milan Pritekelj. Papers in other languages were not edited; the authors alone are responsible for the text. English translations were done by Simon Pire and partly by the authors themselves. The authors themselves are liable for the contents of the papers Published by the Geological Survey and the Slovene Geological Society Printed in 600 copies Price US $ 80.0 Printed by the Delo-Tiskama d.d., Ljubljana, Dunajska 5, in 1997 Financed by the Republic of Slovenia, Ministry of Science and Technology and the Ljubljana Geological Survey, Institute of Geology, Geotechnics and Geophysics GEOLOGIJA 39, 1-311 (1996), Ljubljana VSEBINA - CONTENTS Buser, S. V spomin prof. dr. Jožetu Duhovniku .......................................... 5 Dimkovski, T. Ob 50. obletnici Geološkega zavoda za Slovenijo................................. 9 Paleontologija - Paleontology Debeljak, I. Ontogenetic development of dentition in the cave bear............................ 13 Ontogenetski razvoj zobovja pri jamskem medvedu .............................. 30 Ramovš, A. Solenopora ladinica n. sp. und Solenopora suhadolica n. sp. (Rotalgen) und Paragondolella? trammeri (Kozur, 1972) (Conodonta) aus dem Ladin (Mitteltrias) bei Suhadole, ostlich von Ljubljana, Slowenien ................. 79 Solenopora ladinica n. sp. in Solenopora suhadolica n. sp. (rdeče alge) in Paragondolella? trammeri (Kozur, 1972) (Conodonta) iz ladinija (srednji trias) pri Suhadolah, vzhodno od Ljubljane .............................. 79 Pejović, D. Pironaea buseri n. sp. from olistostromal breccia of Paleocene flysch by Anhovo ................................................................. 91 Stratigrafija - Stratigraphy Grad, K., Dozet, S., Petrica, R. & Rijavec, L. Pseudosocka Beds with Coal in Borehole Tdp-1/84 Trobni Dol (Eastern Sava Folds, Slovenia) ................................................ 97 Psevdosoteške plasti s premogom v vrtini Tdp-1/84 Trobni Dol (vzhodne Posavske gube) ..................................................... 116 Dozet, S. Ambrus Beds - Important Key for Interpretation of Neocomian Paleogeography, Sea-Level Changes, Depositional Setting and Tectonics in Suha Krajina Area (Slovenia) ............................................................. 119 Ambruške plasti in njihov pomen za interpretacijo neokomskih paleogeografskih, evstatičnih in tektonskih razmer na območju Suhe krajine (Slovenija)............... 119 Sedimentologija - Sedimentology Ogorelec, B. & Bu^er, S. Dachstein Limestone from Km in Julian Alps (Slovenia) .......................... 133 Razvoj dachsteinskega apnenca na Krnu v Julijskih Alpah......................... 144 Kralj, P Lithofacies characteristics of the Smrekovec volcaniclastics, northern Slovenia....... 159 Litofacialne značilnosti smrekovških vulkanoklastitov (severna Slovenija)........... 183 Skabeme, D. Interpretation of Depositional Environment Based on Grain Size Distribution of Sandstones of the Val Gardena Formation in the Area Between Cerkno and Smrečje, Slovenia ........................................................... 193 Interpretacija sedimentacijskega okolja na osnovi porazdelitve velikosti zm peščenjakov grödenske formacije na območju med Cerknim in Smrečjem, Slovenija ... 208 Organska geokemija - Organic geochemistry Ogorelec, B., Jurkovšek, B., Šatara, D., Baric, G., Jelen, B. & Kapović, B. Potencialnost karbonatnih kamnin za nastanek ogljikovodikov v zahodni Sloveniji ... 215 Carbonate rocks of west Slovenia as potential sources for hydrocarbons............. 232 Tektonika - Tectonics Premru, U. Rezente tektonische Aktivität des Krško-Einbruchstales (Slowenien) ............... 239 Recentna tektonska aktivnost Krške udorine .................................... 280 Placer, L. O premiku ob Savskem prelomu............................................... 283 Displacement along the Sava fault............................................. 285 Placer, L. Pecin nariv ob Periadriatskem lineamentu ...................................... 289 Peca thrust at the Periadriatic lineament ....................................... 300 Diskusije - Discussions Jelen, M. Prispevki slovenskih geologov v časopisu Delo................................... 305 Navodila avtorjem.............................................................. 307 Instructions to authors.......................................................... 309 GEOLOGIJA 39, 5-311 (1996), Ljubljana V spomin prof. dr. Jožetu Duhovniku v maloštevilnih vrstah slovenskih geologov je smrt v kratkem času zopet zarezala globoko vrzel: 4. decembra 1996 je sklenil svojo življe- njsko pot Jože Duhovnik, redni profesor za mineralogijo, petrografijo in nauk o rudiščih na Univerzi v Ljubljani. Z njim sta rudarska in geološka stroka izgubili živo vez z enim naših najboljših poznavalcev, ki so do največje po- tankosti poznali naša rudna bogastva in mag- matske kamnine ter načine in vzroke njihove- ga nastanka. Prof. Duhovnik se je rodil 9. marca 1913 v Mednem. Po maturi na klasični gimnaziji v Ljubljani se je leta 1932 vpisal na rudarski od- sek tehniške fakultete Univerze v Ljubljani. Že kot študenta so ga zanimale magmatske kamnine in za geološko-petrografsko študijo o peračiških tuf ih je 1935 prejel svetosavsko na- grado. Študij na ljubljanski Univerzi je 1937. leta končal z odličnim uspehom in prejel diplomo rudarskega inženirja. Po diplomi je nastopil službo pomočnika glavnega geologa rudnika Trepča Mines v Zvečanu pri Kosovski Mi trovici. Ta služba je prof. Duhovnika zaznamovala za vse ži- vljenje. V Starem Trgu se je seznanil s svetovno znanim mineralnim bogastvom, ki do takrat še ni bilo primerno raziskano. In potegnilo ga je v svet mineralov in rudišč ter v razlago njihovega nastanka. Temu poslanstvu je ostal zvest do konca svojega življe- nja. Med svojim službovanjem v Trepči je opravljal rudarsko-geološke in geološke ra- ziskave še na drugih svinčevo-cinkovih rudiščih na obrobju Kopaonika in v Makedo- niji. Tako se je spoznal z globljim bistvom nastanka rudišč in postal praktični stro- kovnjak ter raziskovalec le-teh še pred svojim prihodom na Univerzo v Ljubljani. Na inštitut za mineralogijo Univerze ga je leta 1940 povabil svetovno znani ruski strokovnjak za rudarsko geologijo prof. Nikitin, ki je takrat predaval na tehniški fa- kulteti. In začela se je pedagoška pot mladega asistenta pripravnika, do takrat že izo- blikovanega raziskovalca. Kot asistent je vodil vaje iz kristalografije, mineralogije, petrografije in nauka o rudiščih pa tudi vaje iz laboratorijskega preiskovanja mine- ralov. Leta 1943 je opravil disertacijo z naslovom Izpremembe sestava granita in apnenca ob njunem kontaktu. Istega leta je bil predlagan za docenta za nauk o rudi- ščih, vendar je bilo imenovanje potrjeno šele 1945. leta. Konec leta 1946 je napredoval 6 Stanko Buser v izrednega profesorja na tehniški fakulteti in postal predstojnik inštituta za minera- logijo, petrografijo in geologijo. Po odhodu prof. Marica v Zagreb je 1947 prevzel tudi vsa predavanja iz teh predmetov in še iz geologije nafte in premogov. Leta 1956 je po- stal redni profesor. V nekaj letih se je število študentov rudarstva, metalurgije, geolo- gije in kemije, za katere je opravljal predavanja in vaje, izredno povečalo. To je bilo zlato obdobje rudarskega in metalurškega visokega šolstva. Prof. Duhovnik, ki je poučeval stotine študentov, je bil na faktuleti zares od zore do mraka. Le tisti, ki smo bili njegovi študenti, moremo šele po dolgih letih svojega dela presoditi, kakšno ogromno breme je z vsemi svojimi zadolžitvami nosil skoraj dve desetletji. Danes nas opravlja to delo več profesorjev in asistentov. Za uspešen študij pri vseh omenjenih predmetih je bilo treba pripraviti tudi pri- merna skripta. Skrbeti pa je moral tudi za stalno dopolnjevanje izredno bogate zbirke mineralov, rud in kamnin, ki jo je v večjem delu ustvaril že prof. Hinterlechner. V svo- jem izrednem spominu je imel prof. Duhovnik "zapisanih" prek 10.000 primerkov bo- gate zbirke. Zavedal se je, kako težko je nabaviti lepe primerke, zato smo študenti smeli na praktični študij v zbirko le nekaj dni pred izpitom. Poleg pedagoškega dela je bil prof. Duhovnik strokovni sodelavec Geološkega za- voda v Ljubljani in geološkega inštituta SAZU. Bil je tudi med ustanovitelji sloven- ske geološke revije Geologija in član njenega prvega uredniškega odbora. Kot odlični poznavalec rudnih nahajališč je preučeval tudi slovenska rudišča ter rudišča in rude barvnih kovin v Srbiji, Makedoniji, Črni gori in Bosni, za katera je veljal kot eden najboljših poznavalcev. Še posebno skrb je namenil raziskavam šamozitnih rud Bosne, Srbije in Makedonije ter manganove rude v Bosni. Spoprijel pa se je tudi z raziskavami kamnin in rud iz daljne Etiopije in Alžirije. Za potrebe rudnikov in delo- ma za metalurške obrate je opravljal razne raziskave in podal številna strokovna mnenja. Njegovo delovanje pa ni bilo usmerjeno samo na takratno ozemlje Jugoslavije, ampak je kot štipendist UNESCA 1958. leta obiskal tudi nekaj znamenitih univerz in rudarskih obratov v ZDA. Kot strokovnjaka za rudišča ga je pot zanesla tudi v Grčijo in Bolgarijo, kjer je spoznal najvažnejša rudišča in nahajališča drugih mineralov. Kot strokovnjak za petrografijo je raziskoval magmatske kamnine Črne gore in jih primerjal s slovenskimi. Na prvem jugoslovanskem geološkem kongresu na Bledu je podal pregled magmatskih in metamorfnih kamnin Slovenije. Vrsto let je s sodelavci raziskoval triasne magmatske kamnine in njihove tufe na Jelovici, v okolici Cerkna in Idriji. Nemalo dela mu je dalo tudi večletno predstojništvo odseka za geologijo in oddel- ka za montanistiko ter članstvo v raznih komisijah na fakulteti in univerzi. Imel je odličen čut za slovenski jezik in zato je kot terminološki svetovalec več let sodeloval pri pisanju Slovarja slovenskega knjižnega jezika. Mnogo let je sodeloval tudi pri ter- minološki komisiji za geologijo pri SAZU. Ob svojih težkih pedagoških obremenitvah je našel tudi čas za raziskovanje in pisanje znanstvenih in strokovnih objav. Velika škoda je, da zaradi pomanjkanja časa ni uspel večino svojega znanja preliti na papir, zato so njegovi objavljeni prispevki - gledani z današnjimi merili - številčno res malo skromnejši. Nehote pa se moramo upravičeno in pošteno vprašati, kaj ni morda celo večja vrednost znanje, ki ga je prof. Duhovnik "prelil" iz svoje zakladnice v svoje študente, ki lažje in dovolj uspešno nadaljujejo njegovo delo. Še posebno je skrbel za popularizacijo geološke vede v širši javnosti. Na RTV je imel več poljudnoznanstvenih predavanj o novostih iz mineralogije, petrografije in nahajališčih mineralnih surovin ter o načinih njihovega odkrivanja. Svetu mineralov v spomin prof, dr. Jožetu Duhovniku_7 je posvetil celo samostojno knjižico. Oglašal se je tudi v Proteusu, kjer je še posebno natančno poročal o prvih vzorcih kamnin, ki jih je človek prinesel z Lune. Številni študenti geologije, rudarstva, metalurgije, kemije in fizike bodo prof. Duhovnika ohranili v spominu kot človeka izrednega spomina in doslednega, stroge- ga moža do sebe in do drugih. Za navidezno trdim in nepopustljivo zahtevnim znača- jem se je skrival človek, ki je skušal biti pravičen do vsakogar, kar mu je v večini pri- merov tudi uspelo. Presenečal nas je s svojim pomnenjem stotine imen svojih študen- tov. V sebi je nosil pravi računalnik s podatki o mineralih, kamninah in rudnih naha- jališčih. Ta njegov spomin nas preseneča še danes. Tisti, ki nadaljujemo njegovo delo, lahko s ponosom rečemo: "Imeli smo maloštevilne, vendar izredno sposobne profesor- je in mednje nedvomno sodi profesor Duhovnik." Po svoji upokojitvi je prof. Duhovnik še dolgo prihajal med slovenske geologe. Po predavanjih v Slovenskem geološkem društvu ni skoraj noben diskusijski večer minil brez njega. V slovensko geologijo je bil globoko vraščen z močnimi koreninami in človek kar verjeti ne more, da ga ni več med nami. Še vedno pa je prisoten v našem spominu z vsemi svojimi predavanji in še posebno s sklepnimi terenskimi vajami po nekdanji Jugoslaviji. Prof. Duhovnik je s svojim trdim, nekaj deset let trajajočim pedagoškim delom dal neizbrisen pečat mnogim generacijam odličnih strokovnjakov, ki nadaljujejo njegovo delo. Raziskave in delo, s katerim nadaljujemo njegovi nekda- nji študenti in sodelavci, naj bo topla zahvala našemu profesorju Jožetu Duhovniku. Stanko Buser GEOLOGIJA 39, 9-311 (1996), Ljubljana Ob 50. obletnici Geološkega zavoda za Slovenijo v letu 1996 je Inštitut za geologijo, geotehniko in geofiziko praznoval 50. obletni- co ustanovitve Geološkega zavoda za Slovenijo. S posebno uredbo je vlada Ljudske republike Slovenije 7. maja 1946 pri Ministrstvu za industrijo in rudarstvo ustanovila samostojno geološko ustanovo Geološki zavod za Slovenijo. Naloga Zavoda je bila, da usmerja, razvija in opravlja vse vrste geoloških raziskav za potrebe gospodarstva in razvoj geoloških ved. Zaostanek v razvoju geologije in pomanjkanje strokovnjakov je ob vse večjih potrebah razvijajočega se gospodarstva zahtevalo od tedaj malošte- vilnih sodelavcev velike napore, določitev vsebine dela in oblikovanje ustrezne orga- nizacijske oblike. Po daljših razgovorih predstavnikov Zavoda, Univerze, upravnih in gospodarskih ustanov so bile določene Zavodove dejavnosti, katere v glavnem še da- nes opravlja Inštitut za geologijo, geotehniko in geofiziko. Sprejet je bil naslednji predlog Zavodove dejavnosti: 1. geološko in petrografsko kartiranje in geofizikalno merjenje 2. raziskave nafte, premoga, rud in nekovin 3. inženirskogeološko in hidrogeološko raziskovanje a) fundiranje gradbenih objektov b) pitna in industrijska voda c) topli in mineralni vrelci č) hidrogeologija Krasa 4. kartografija 5. laboratorijske preiskave: petrografske, paleontološke, kemične, tehnološke in geomehanske 6. arhiv in knjižnica 7. geološki muzej z zbirkami in katastrom gradbenega materiala 8. izdajanje publikacij Predlog je bilo težko uresničevati, ker je bilo v Sloveniji le 5 geologov, ki pa so bili vsi zaposleni na visokih šolah. Med zaposlenimi Zavod ni imel nobenega geologa in v prvih letih so naloge opravljali zunanji sodelavci in to predvsem visokošolski profe- sorji, pa tudi študenti geologije in rudarstva. Po decentralizaciji gospodarstva leta 1950 je Zavod prešel pod upravo Sveta za energetiko in ekstraktivno industrijo LRS in se je z odredbo vlade LR Slovenije dne 8. julija istega leta preimenoval v Upravo LR Slovenije za geološka raziskovanja. Sočasno je z isto odločbo prevzel Zavod tudi operativno vodstvo novo ustanovljenega Podjetja za globinsko vrtanje. Za upravnika je bil imenovan inž. Danilo Jelene. Sredi leta 1952 je prišlo do ponovne spremembe, ko se je Uprava LRS za geološka razisko- _Trajan Dimkovski vanj a združila s Podjetjem za globinsko vrtanje in se preimenovala v Geološki zavod LR Slovenije v Ljubljani. Upravno je bil Zavod podrejen Svetu vlade LRS za indus- trijo. Ker so se sredstva za geološko-rudarske raziskave v družbenem načrtu zmanjše- vala, je moral Zavod preusmeriti program dela glede na potrebe gospodarskih orga- nizacij. Zaradi spremenjenega načina financiranja, je bil Zavod leta 1954 razglašen za finančno samostojno enoto in se je preimenoval v Geološki zavod Ljubljana. Od tedaj se je Zavod razvijal hitreje. Po uspešni uveljavitvi tako v Sloveniji kot v drugih republikah tedanje Jugoslavije je Zavod kot prva slovenska raziskovalna organizaci- ja pričel z raziskovalnimi deli tudi v tujini. Hiter razvoj Zavoda kaže število zaposle- nih. V letu 1947 so bili 4 zaposleni, leta 1959 je bilo 347 zaposlenih in v letu 1980 sku- paj 3000. Veliko organizacijsko spremembo je Zavod doživel leta 1979 z ustanovitvijo šestih TOZD-ov, ki so se leta 1990 na podlagi Zakona o podjetjih preoblikovali v Inštitut za geologijo, geotehniko in geofiziko in štiri samostojna podjetja. Ves čas delovanja je imel vidno vlogo raziskovalni del Zavoda, zaradi česar je bil Zavod tudi ustanovljen. Inštitut je s svojo dejavnostjo edina ustanova v Republiki Sloveniji, ki kompleksno rešuje vse vrste fundamentalnih in aplikativnih nalog, veza- nih na geologijo oziroma na raziskovanje zemeljske skorje. Po osamosvojitvi Sloveni- je se je interes države za geološke raziskave kar naenkrat zmanjšal. Za to je verjetno več vzrokov. Eden je vsekakor tudi ta, da geologija nima resornega ministrstva. V preteklosti so programe usklajevali prek Zveznega geološkega zavoda v Beogradu. Res je, da so danes potrebe drugačne, kakor so bile v preteklosti. Zmanjševal se je in- teres za mineralne surovine, kot so premog, uran, kovine. Zato pa pridobivajo pomen pitna voda, varstvo narave in raba prostora. Upajmo, da bomo kljub trenutnemu ner- azumevanju vladnih resor j ev uspeli prikazati pomen geoloških raziskav za uspešno in racionalno delovanje države in dobili podporo za nadaljnji obstoj Inštituta. V svoji petdesetletni zgodovini so delavci Inštituta skupaj z drugimi zavodi in sodelavci dosegli pomembne rezultate na vseh področjih svoje dejavnosti. Nemogoče je v kratkem prispevku opisati vse pomembne dosežke; naj navedem samo nekatere: izdalane so Osnovna geološka karta Slovenije v merilu 1:100.000, Metalogenetska karta. Geofizikalne karte in še cela vrsta drugih tematskih kart. Skupaj z rudniškimi službami smo raziskali vsa slovenska premogišča: Velenje, Trbovlje, Senovo, Hrast- nik, Kanižarica, Rudnika Idrija in Mežica, Rudnik Žirovski vrh in številna nekovins- ka nahajališča. Danes so ti rudniki res v večini že zaprti, vendar so bili v preteklosti pomembni za današnjo stopnjo gospodarskega razvoja Slovenije. Z globinskimi vodnjaki smo zajeli termalne in mineralne vode v Radencih, Rogaški Slatini, Čateških Toplicah, Šmarjeških Toplicah, Dolenjskih Toplicah, Atom- skih toplicah, Dobrni, Laškem, Moravcih, Ptujskih toplicah in Zrečah. Najpomemb- nejši pa so rezutlati raziskav in zajetja pitne vode iz globinskih vodonosnikov, ki postajajo vedno pomembnejši zaradi onesnaženosti aluvialnih vodonosnikov. Nič manj niso pomembni rezultati raziskav o mehaniki tal. Prvi smo v Sloveniji začeli razvijati in izvajati sistem za globoko temeljenje v slabonosilnih tleh. Uspešno smo opravili zahtevne raziskave za projektiranje avtoceste čez Ljubljansko barje in za sanacijo številnih plazov. Pomembne so bile geološke raziskave za lociranje predora Karavanke in geološke spremljave pri gradnji le-tega. Za dosego omenjenih rezulta- tov so pripomogle številne znanstvenoraziskovalne naloge iz geoznanosti. Ne nazad- nje ne pozabimo na uspešno izvedene projekte v več kot 20 državah Evrope, Afrike in Južne Amerike. Ob 50. obletnici Geološkega zavoda za Slovenijo_П Številni uspešno opravljeni projekti so razultati nenehnega vzgajanja potrebnih strokovnjakov. S prihodom prvih diplomantov geologije v letu 1952 se je pričela nagla rast Zavoda. V letu 1949 je imel Zavod 318 delavcev, od tega 4 geologe z visoko izobrazbo. V letu 1952 je bilo 14 geologov, v letu 1959 pa že 33 delavcev z visoko izo- brazbo. Največje število zaposlenih je imel Inštitut v letu 1988 (217), z visoko izo- brazbo 100 delavcev. Danes ima Inštitut 151 zaposlenih. Visoko izobrazbo ima 77 de- lavcev, od katerih je 11 doktorjev znanosti in 13 magistrov. Za takšen razvoj so zaslužni vsi delavci, ki so bili v obdobju teh naših 50-ih let člani Inštituta, ne nazadnje pa so dosežki tudi rezultat tesnega sodelovanja z drugimi organizacijami, predvsem rudniki in Univerzo. Trajan Dimkovski GEOLOGIJA 39, 13-311 (1996), Ljubljana Ontogenetic development of dentition in the cave bear Ontogenetski razvoj zobovja pri jamskem medvedu Irena Debeljak Ivan Rakovec Institute of Palaeontology, Scientific Research Centre of the Slovenian Academy of Sciences and Arts, Gosposka 13, SI-1000 Ljubljana, Slovenia Key words: Ursus spelaeus, Ursidae, dentition, jawbones, ontogenetic develop- ment, growth, age determination, sex dimorphism, mortality. Divje babe I Ključne besedeiUrsus spelaeus, Ursidae, zobovje, čeljustnice, ontogenetski raz- voj, rast, določanje starosti, spolni dimorfizem, mortaliteta. Divje babe I Abstract In this contribution the ontogenetic development of dentition in the cave bear {Ursus spelaeus Rosenmüller & Heinroth) is described up to the age of about four years, when the animals became adult and the formation of their teeth was complet- ed. The process of tooth growth and the replacement of deciduous teeth by perma- nent dentition took place in a similar way as with the present-day brown bear {Ursus arctos Linné). The teeth eruption sequence is the same in both species. The specimens of cave bear jawbones that served for this study were collected from the well-known Palaeolithic site Divje babe I (W Slovenia). Individual age estimations of these jawbones were made on the supposition that a certain ontoge- netic stage in the development of cave bear dentition corresponds to an approxi- mately equal age of an individual as with the brown bean The growth of the jaw, however, was essentially faster in cubs of the cave bear We also presume that the secondary sex dimorphism in cave bears with males having larger jawbones than females was already expressed in the first year of life. With regard to some indices, especially after noting the obvious discordance between the expected and actually observed mortality profile, we should also con- sider another possibility; that ontogenetic development in the cave bear was signifi- cantly slower than in present-day bears. However, this alternative does not seem very probable, because a proper ontogenetic development has its functional impor- tance. A long time iag in the eruption of-permanent molars would mean a certain disadvantage to the species. Kratka vsebina V prispevku je opisan ontogenetski razvoj zobovja jamskega medveda {Ursus spelaeus Rosenmüller & Heinroth) vse do starosti približno štirih let, ko so živali odrastle, njihovi zobje pa so bili dokončno formirani. Proces rasti zob in zamenjave mlečnega zobovja s stalnim je pri jamskem medvedu potekal na podoben način kot 16_v Irena Debeljak pri današnjem rjavem medvedu {Ursus arctos Linné). Zaporedje izraščanja zob je pri obeh vrstah enako. Primerki čeljustnic jamskega medveda, na katerih je opisan ontogenetski razvoj zobovja, so iz znanega paleolitskega najdišča Divje babe I (W Slovenija). Individual- no starost teh čeljustnic smo ocenili glede na domnevo, da določena ontogenetska stopnja v razvoju zobovja jamskega medveda ustreza približno isti starosti osebka kot pri rjavem medvedu. Rast čeljusti pa je bila pri mladičih jamskega medveda vendarle bistveno hitrejša. Domnevamo tudi, da je bil pri jamskih medvedih sekun- darni spolni dimorfizem izražen že v prvem letu življenja; samci so imeli večje čelju- sti od samic. Glede na nekatere pokazatelje, še posebej po očitnem razhajanju med pričako- vanim in dejansko ugotovljenim mortalitetnim profilom, bi morali upoštevati tudi drugo možnost; da je bil ontogenetski razvoj zobovja jamskega medveda bistveno počasnejši kot pri današnjih medvedih. Vendar, ta alternativa se ne zdi zelo verjetna, ker ima primeren ontogenetski razvoj svoj funkcionalen pomen. Dolg časovni zaosta- nek pri izraščanju stalnih molarjev bi za vrsto pomenil določeno pomanjkljivost. Introduction In contrast with the phylogenetic evolution, the ontogenetic evolution of cave bear dentition has not been explicitly described so far, and it is generally little known to the professional public. Most researchers of the cave bear limit themselves to the statement that a certain jawbone is juvenile, which means that it belonged to a cub. Only seldom do the authors (as Rädulescu & Samson, 1959) accompany the photographs or descriptions with more detailed information on the age of the cub. The latter can be estimated by comparison with the present-day brown bear. In the present work all data on teeth eruption in the brown bear are collected that are important for deter- mining the individual age of juvenile jawbones of the cave bear and of other bear species as well. The reason for interest in the age determination of relatively rare juvenile jawbone finds is not simple curiosity. Palaeontologists and archaeologists are also interested in the behaviour of cave bears and the environment in which they lived, especially including the relationship between prehistoric man and bear. From this point of view, the precise assessment of individual ages of jawbones that belonged to cubs less than one year old offers us very important information, i.e. on the season in which the ani- mals died. By all means, the most accurate data on cave bear mortality can be achieved by the age analysis of single, isolated teeth found in tens of thousands in those Palae- olithic cave sites that had also served as typical dens of the cave bear. The individual age of particular juvenile teeth can be correctly estimated, however, only after previ- ous study of their development and degree of formation at various ages on the set of the whole jawbones. Exactly this was the primary reason for our analysis of the jawbones of cave bear cubs from the Palaeolithic locality Divje babe I. This study was the basis for our fur- ther research on the age structure of the cave bear population from the upper part of the Pleistocene deposits (Debeljak, 1996a, 1997). The age analysis was carried out on isolated deciduous teeth d^ and permanent teeth М^. Therefore in the present paper a more detailed description of the ontogenetic development of these teeth is given. Ontogenetic development of dentition in the cave bear_ 17 Previous research Ehrenberg was the first to study the ontogenetic evolution of the cave bear He established the identity of the ontogenetic stages of dentition with those of the brown bear (1931, 640). He described the different steps in the development of mandibles, and he approximately estimated their individual ages (1931, 659-675, 701-703). In those times only scarce data were available on tooth growth in the brown bear, so it is understandable that Ehrenberg's age estimates were imprecise. He concluded that in the well-known locality Drachenhöhle near Mixnitz many remains belong to cubs that perished from exhaustion prior to spring - less than 4 months old. According to Ehrenberg, this age-class was followed by a long gap after which appeared the group of most numerous remains of cubs about 1 year old. The supposed mortality peak at that age was explained as the consequence of complications in eruption of the last, i.e. distal molars. Ehrenberg's interpretation of the presumed absence of remains of 4-10-month-old cubs was that cave bears occupied caves only in winter, during hibernation. This opinion has prevailed among researchers until the present day. Former spectacular ideas of cave bear hunting were withdrawn by sober scientif- ic judgement. After 30 years Ehrenberg obtained good comparative data for the present-day brown bear. He attributed the age of 7 months to an almost complete skeleton of a cave bear cub from Hartlesgraben (1964, 217-219). In the same contribution he cor- rected age estimates of certain mandibles made in 1931. Nevertheless, he remained convinced about the existence of the above-mentioned gap in the age composition of the cave bear remains while explaining the rare remains of 4-10-month-old cubs as an exception that confirms the rule. Musil (1965, 72) sorted the juvenile jawbones of cave bears from the Pod hradem cave according to their progressive ontogenetic development, and described them in detail. However, he did not determine their individual ages. Material and methods The ontogenetic development of cave bear dentition will be described on eleven examples of jawbones from the Palaeolithic site Divje babe I, which is located below the edge of the plateau Šebreljska planota, above the Idrijca River valley (W Slove- nia). The larger part of Pleistocene deposits in the cave originate from the Middle Würm period. All fossil cave bear remains from the Divje babe I are kept in the National Museum of Slovenia in Ljubljana. General information on the locality can be found in Turk et al., 1989a, b and Turk ed., 1997. Age estimations of individual jawbones were made according to Dittrich's (1960) comprehensive data set on present-day bears, and the comparisons with juve- nile jawbones of the brown bear from Slovenia. The sex was determined from the size of the teeth, especially of canines, according to the works of Ko by (1949) and Kurtén(1955). Some facts on the living habits of the brown bear that can also be attributed to its relative the cave bear are summarized from Macdonald ed., 1985, 88-95 and Krystufek, 1991, 191-193. 18_v Irena Debeljak Jawbones and teeth of the cave bear - general The lower jaw of bears consists of two mandible bones (i.e. hemimandibles or mandibles). They are joined in a symphysis that never ossifies. The upper jaw is formed on each side by two paired bones: the premaxilla that bears the incisors and extends to the canine, and the upper jawbone or maxilla. These two bones are fused only in grown up individuals. In jawbones tooth sockets or alveolae appear in which tooth roots are attached. The brown bear as well as the cave bear have in both jaws on each side the follow- ing deciduous teeth: 3 incisors (dil-3), one canine (dc) and usually 3 premolars (d2-4 or p2-4). On each side of the lower jaw of the cave bear the following permanent teeth are present: three incisives (I1.3), one canine (C), usually a single premolar (P^) and three molars (М^_з). In the maxilla there is one molar less. The molars have a broad masticatory surface with numerous low, rounded cusps. Early researches into the morphology of dentition and the skull revealed that the cave bear was almost exclusively vegetarian in habits (cf. Kurtén, 1976). Recent isotopie analyses confirmed this hypothesis (Bocherens et al., 1994). The permanent dentition of bears was described in detail by Rode (1935). Kob y (1952) and Rädulescu and Samson, (1959) described the deciduous dentition of the cave bear. For the orientation of jawbones and teeth a variety of terms is used. In this paper the following terms are met: Front - anterior - mesial. Back - posterior - distal. (This is simplified! The listed terms are not equivalent generally.) Side facing the cheeks - buccal - lateral. Towards the tongue - lingual (in the mandible) or palatal (in the maxilla). The biting (upper) surface or edge of the teeth is called occlusal. The ontogenetic development of dentition in bears (familiy Ursidae) Certain data on the eruption of permanent teeth in present-day bears can be found in the following references: Pohle, 1923; Couturier, 1954; Rausch, 1961; Marks and E r i c k s o n, 1966. However, the most detailed study of the development of decid- uous dentition and its replacement by permanent teeth in the brown bear was done byDittrich (1960). He established that this process is practically the same and also synchronous in other bear species. The succession of eruption of individual teeth from the gums is presented in figure l.Dittrich's other data on the ontogenetic develop- ment of dentition in bears can be summed up in the following principal points: The cubs are born toothless. The first milk teeth start erupting during the second month of life, and they come into position during the third month. The first perma- nent molars start piercing through the gum in the fifth month of life. The cubs are able to chew solid food only after they get the first pair of permanent molars (М^&М^). The deciduous dentition has almost no functional meaning in chewing. The deciduous teeth are shed by the end of the 15th month. The eruption of the last perma- nent teeth is accomplished at a mean age of one year and a half. Dittrich(1960, 119-123) found out that the body weight in bears generally does not influence the growth and the rate of eruption of teeth. Also individual differences in this process are relatively small (see fig. 1). The disposition of deciduous and permanent teeth in the jaws of a brown bear cub is illustrated by figs. 2a and 2b. Ontogenetic development of dentition in the cave bear 17 Fig. 1. Ontogenetic development of dentition in the brown bear up to the age of 16 months (after Dittrich, 1960, 86, fig. 27). Individual deciduous teeth (left) are marked with a dotted pattern, and permanent teeth (right) with black. An arrow at the beginning or at the end of the symbols indicates the period in which the start of eruption of milk and permanent teeth, or shedding of milk teeth could take place. The length of the arrow therefore illustrates individual differences SI. 1. Ontogenetski razvoj zobovja pri rjavem medvedu do 16. meseca starosti (po Dittrichu, 1960, 86, si. 27). Posamezni mlečni zobje (levo) so označeni pikčasto, stalni zobje (desno) pa s čmo barvo. Konica na začetku in koncu simbolov nakazuje obdobje, v katerem lahko pride do začetka izraščanja mlečnih in stalnih zob oziroma do izpada mlečnih zob. Dolžina konice torej ponazarja individualne razlike The ontogenetic development of dentition in the cave bear The first three months Osteological remains of unborn animals (fetuses) and of those cubs vvrho died at birth or shortly thereafter (neonates), are preserved only exceptionally in the Pleis- tocene localities. Nevertheless, such finds are not so rare in the Divje babe, because the cave served for long millenia as a den, especially to cave bear females who whelped their young in the winter months from December to February (Turk et al., 1989b; Debeljak, 1997). The thin and fragile (owing to porosity) mandibles of still unborn or newborn bears are 2-3 cm long and only around 5 mm wide. Cave bear young were born toothless. The same is true in present-day bears. Already in the first week of the brown bear's life, the germs of deciduous teeth can be 20_v Irena Debeljak Fig. 2a. X-ray photograph of the skull of an approximately four-month-old brown bear cub from the Pyrenees (after Couturier, 1954, 142, PI. 30). The individual age was estimated after Dittrich's (1960) data. Natural size SI. 2a. Rentgenski posnetek lobanje približno štiri mesece starega rjavega medveda s Pirenejev (po Couturieru, 1954, 142, tab. 30). Ocena starosti po Dittrichovih (1960) podatkih. Naravna velikost Ontogenetic development of dentition in the cave bear__19 Fig. 2b. Schematic illustration of fig. 2a (modified after Couturier, 1954, 143, PL 30). Small letters mark decidu- ous teeth, and capital letters permanent teeth SI. 2b. Shematska ponazoritev slike 2a (prirejeno po Couturieru, 1954, 143, tab. 30). Male črke označujejo mlečne zobe, velike črke stalne zobe 20_v Irena Debeljak found in preparations of their jaws: small, hollow caps of crowns that had not yet erupted from the gums (Dittrich, 1960, 11, figs. 1, 2). This neonatal phase of the ontogenetic evolution is represented by the following example: 1. (PI. 1, figs. 1, 2) - Left and right mandibles of two neonates which died in the first days after birth: For the sake of clarity the mandibles in the illustration (PL 1, fig. 1) are joined in their natural position, although they did not belong to the same individual. In the lateral view (PI. 1, fig. 2), the body of the mandible appears semicir- cularly curved, which is typical for neonates. On the broken upper surface, the germs of both deciduous canines are clearly visible, and even the germ of the protoconid of the last deciduous tooth d^ or p^, as marked by some researchers. (The protoconid is the central, largest cusp on the mentioned tooth). The germs of deciduous teeth were originally enclosed in the bone. At that time the alveolae through which the growing milk teeth would later erupt were still forming. The length of the described mandible was around 4 centimeters, the same as in the newborn cubs of the brown bear. Ehrenberg (1973) documented the find of an almost complete neonatus skeleton of about 10 days of age from the Austrian locality Salzofenhöhle. After various mea- surements and reconstruction that were made with the bones he concluded that the young of the cave bear could have been only minimally larger at birth than those of the brown bear. In a brown bear litter there are usually two or three cubs of the size of a rat, weighing only 350-400 grams. They are hairless, blind and entirely helpless. They are not able to maintain their body temperature, so they can survive only with their caring mother in a den protected from the cold. In the second and third months of life the cave bear cubs most probably stayed in the den, i.e. in the cave. The female did not leave them. During the long months before the advent of spring she lived only on fat reserves collected during the late summer and autumn. For her young this was the time of lactation, of an exclusively milk diet. Meanwhile, all the deciduous teeth gradually erupted from the gums. Below them, hidden in the bone, the crowns of the permanent teeth were forming and strengthen- ing. The eruption sequence of individual deciduous teeth can be reconstructed with the help of data on the brown bear (fig. 1). This period of ontogenic development is represented by the following two examples: 2. (PI. 2, figs. 1-3) - The mandible of a cub about 2-2.5 months old: The crown of the first permanent М^ molar is already formed; on the x-ray photograph (PI. 2, figs. 2, 3) it is clearly visible as a thin, hollow shell encased in the jawbone. Also the first millimeters of the root wall started growing. Within the mandible the tips or crown germs of P4 and C are hidden. The permanent teeth developed in hollow chambers of the mandible with thin partitions in between. On the upper side of the mandible, in the place where М^ would later erupt, a narrow fissure is open. In front of it appear small holes; these are alveolae in which the roots of the deciduous premolars d4 and dg were anchored. They indicate that the mentioned milk teeth had already erupted from the jawbone, so the cub most probably was not younger than two months. The mandible was approximately of the same length as in an approximately four-month- old brown bear (fig. 2a), but much more robust. 3. (PI. 3, figs. 1-3) - Both halves of the mandible of a cub about 2.5-3 months old: The furrow broadened in the place where in a month or two М^ would start erupting. Observed from above, the dark crown of М^, fragile like an egg shell, is visible through it. The upper quarter of the М^ root was already formed (PI. 3, figs. 2, 3); it is as thin as paper however. Also the crowns of the permanent incisives and the germs of C and P4 teeth are concealed in the jawbone. On the upper side of the mandible the Ontogenetic development of dentition in the cave bear 21 alveolae of deciduous teeth are clearly visible. At this age almost all the deciduous teeth were in place, although they are not preserved here in this specimen. (The process of the eruption of milk teeth can be illustrated on an example of d4: at the age of 1-2 months the crown of d^ was enclosed in the jawbone; the crown was brown in color, dull and very fragile. Soon afterwards first the tip of the protoconid, i.e. the cusp that first breaks through the gum, became lighter colored, and later also the remaining part of the crown. In 2- to 3-month-old cubs the crown of the completely erupted d^ was already strengthened, normally bright, and with enamel of character- istic lustre. The root was, however, still hollow, and consequently rather fragile.) The mandible described is approximately of the same size as in a half-year-old brown bear. The sketch of an essentially smaller mandible of a three-month-old pre- sent-day brown bear, as published by Pohle (1923), can serve for comparison. The fourth to sixth months of life By the fourth month the bears already have all the deciduous teeth in place. The more or less formed crowns of the permanent teeth are meanwhile enclosed in the jawbones, where they gradually strengthen. For example, below the deciduous tooth d^ there is already the crown of the permanent P^ in a four-month-old cub (figs. 2a, 2b). With the progressive growth of its root the permanent tooth starts protruding and replacing the milk one. In this process, the strong protoconid of the P^ crown wedges between the two halves of the d^ root, and it gradually induces the contact resorption of the root. A similar result also occurs in the upper pair of the deciduous d"^ and per- manent P^. During the fifth month, the first permanent molars (Ml) start erupting. First the frontal part of the М^ tooth with protoconid and paraconid appears from the gums, and soon afterwards the posterior part of the crown with metaconid and talonid (Dittrich, 1960, 80-81). The dentition of the brown bear cub in fig. 2a is in the stage just described. Couturier (1954, 142-143) published this x-ray picture of a cap- tured cub, and attributed an age of three months to it. According to Dittrich's (1960) data it is, however, evident that this cub was in fact older, at least 4 months of age. Rädulescu and Samson (1959, 211, fig. 11) published a photograph of the mandible of an approximately 4-month-old cave bear Musil (1965, 72, PL 3, fig. 10) presented a specimen of the mandible that belonged to a possibly somewhat younger cub. A picture of a cave bear jawbone that would be typical for a five-month-old cub (М^ or М^ in the eruption phase) has not yet been found in the literature. In the osteological collection from the Divje babe I site there is no jawbone of a 4- to 5-month-old cub available that would be fit for publication. As a matter of fact, this is not a mere chance, since among the very numerous isolated deciduous teeth only very rare specimens were found that could be attributed to this age class. (Such are, for example, the upper or the lower d4 with strengthened root which is already somewhat resorbed at the apex. Individual cusps on the crown are rounded, and often bear tiny wear facets. Debeljak, 1996a, 1997). Evidently the mortality of four- to five-month-old cubs in the Divje babe cave was much lower than at the younger age. The present contribution does not intend to discuss possible reasons for varying mortality rates during the year. It should only be mentioned that the fourth to sixth month of life was the time of spring. The brown bear cubs accompanied by their 22_v Irena Debeljak mother leave the den after the third month, in April or May, at times as late as the beginning of June. The same practice was probably true of the cave bear. In addition to the milk sustenance that they get from their mother, the living bears also begin to chew solid food, starting at the fifth or sixth month. This becomes possi- ble only after they get the first pair of permanent molars (Dittrich, 1960, 14-15). The small, pointed milk teeth are of little use for chewing. Only the new back-teeth can provide the necessary mastication surface. The seventh and eighth months of life Summer finally arrived. For the whole bear family came the time of intensive feeding. In the following months they had to collect a sufficient amount of fat, neces- sary for survival through the next winter. The dentition of 6-8-month-old cubs were then in the following condition: 4. (PI. 4, figs. 1-5) - The mandible of a female approximately 6-7 months old: Con- siderable progress is evident, as compared to the specimen discussed earlier (PI. 3). The crowns of all the permanent teeth are already formed. Later they would not grow any more, but only become stronger with the secondary dentine which was gradually filling their interior. The М^ of this cub has been "in place" for a month or so, and it has more than 4/5 of the crown developed. The crown is moderately strengthened, but the root is still entirely hollow and open at the apexes (PI. 4, fig. 5). М^ shows the first signs of wear, which indicates that the animal had already chewed hard food for some time. As a consequence of chewing numerous tiny wear facets developed, showing a characteristic glossy surface. It is obvious that the ontogenetic development of the individual teeth progressed at different rates, in accordance with the data for the brown bear presented in fig. 1. The М^ surpassed the other permanent teeth in devel- opment. It is followed by 1^, which was at that time already in place, but is not pre- served here. I2 emerged through the gum shortly before the cub died. P^ and Mg were just prior to the eruption phase. The tops of their crowns are already of lighter color. The last incisor I3 is still enclosed in the mandible, and can be seen only on the x-ray photograph. The same applies to the canine that has only the crown, but not yet the root. In this phase of growth, P^ was pushing the overlying d^ and dg deciduous teeth from the jaw. Their roots were at that time already strongly resorbed. At the latest in a month or so d^ (not preserved in our specimen) would fall out in a natural way with an entirely resorbed root. (In bears, the last deciduous premolar d^ is in use for a short period only. It takes part in chewing solid food for only about 3 months, therefore its occlusal surface is scarcely ever heavily worn away.) The size of the described mandible corresponds to a brown bear cub about one year old (PI. 9, fig. 1; PI. 10, fig. 2). Are our age estimates correct? Was the development of dentition in the cave bear faster, or perhaps slower than in the living brown bear? Let us discuss this problem with reference to the example of the above described mandible: It is physiologically necessary that in the sixth or at least in the seventh month the ontogenetic development results in the inclusion of the first pair of permanent molars in dentition. This is valid for the present-day brown bear, and could not have been much different for the cave bear As already mentioned, during the transition to solid plant food the most important part is assumed by the first permanent molars Ml. The mother's milk gradually ceases to suffice for growth, and the cubs have to start feed- ing on solid food, too. The deciduous teeth, with the exception of the last d4 premo- Ontogenetic development of dentition in the cave bear_ 25 lars, are so tiny that they have practically no functional importance for chewing hard plant food (Dittrich, 1960, 14-15, 50, 81-82). The age of the described mandible of the cave bear, therefore, cannot differ much from our estimate. In the case of a much higher age, М^ with its chewing surface would not be "in place" soon enough to enable adequate feeding, so that the growing cub could make the best use of the summer and autumn food supply. On the other hand, the size of the mandible and the wear of М^ that could not be caused by mere milk nutrition testify against a lower age. Perhaps this could be proven by isotopie analyses of dental tissues. In my opinion errors in the age estimates are not large, and certainly not essential. I consider that concerning the ontogenetic development of cave bear dentition, the comparison with the brown bear is appropriate. 5. (PI. 5, figs. 1, 2) - The mandible of a male bear about 6.5-7.5 months old: The size of the mandible is almost equal to that of a brown bear at the age of a year and a half (PI. 16, figs. 1, 2; PI. 18, fig. 1). The anterior part of М^ protrudes out of the jaw- bone. The enamel becomes lighter in color during this process. In the canine the wall of the root has just started forming. The crown of Mg is enclosed in the ascending mandibular branch (i.e. ramus mandibulae), and is consequently of typical dark brown color, without lustre. A thin bone wall above Mg is broken, so it can be observed that the occlusal surface is turned lingually (inwards, towards the tongue), and it stands almost vertically with the anterior part oriented downward. Only after subsequent growing of the jawbone would the space for the two distal molars be cre- ated. (In bears, Mg rotates 90° in two directions in order to be included in the tooth row, while the jaw grows to accommodate it.) 6. (PI. 6, figs. 1-4) - The mandible of a female about 6.5-7.5 months old: The jaw- bone belonged to a cub of a similar age as in the previous case, it was possibly only a trifle older. М^ was for a time "in place" and in use. For this reason its crown bears shallow wear facets approx. up to 3 millimeters in size. The root wall is almost entirely formed, but still open at the ends (PI. 6, fig. 4). More than half of the Mg crown already protrudes from the mandible, and about one half of the root is formed. Its wall is very thin, and the interior hollow (PI. 6, fig. 4). The М^ root is more devel- oped and firm; the wall is about one millimeter thick. In the same phase of the onto- genetic development or at the same age, the last lower Mg molar has no root at all, and the thin, flat crown of this tooth could easily be broken in pieces (cf. Pl. 5). It is quite obvious that individual teeth of the same cub were developed to various stages, they were, therefore, of varying mechanical resistance, and consequently did not have equal possibilities to be preserved as fossils. In analyses of various isolated teeth we should take into account different degrees of taphonomic losses. Such differ- ences occurred either as a result of the diverse shapes and sizes of individual teeth, or owing to various degree of ontogenetic development, which meant unequal firmness at a certain age. It is interesting to compare the mandible sizes in plates 4-6 (and also 11-15). Nor- mally, the size of the bone depends upon the age of the individual. However, it is noticeable that the mandible size can be rather variable at a similar age as well - in proportion to the size of permanent teeth. The latter occupy practically the entire jawbone, as can be clearly seen on the x-ray photographs. Larger dentition also requires more space. The following conclusions can be made: 1. The cave bear had markedly larger sized dentition than the present-day brown bear. It is understandable that its jaws had to be much larger and more robust in the 24_v Irena Debeljak same ontogenetic phase and age. Although the cave bear cubs were as small at birth or perhaps only minimally larger than those of the brown bear, the growth of their jaws in the following months was essentially faster For instance, it was indicated that the mandible of a cave bear hardly much older than half a year (PI. 5) can be of the same size as that of a one-and-a-half-year-old brown bear Was the rest of the body also that much larger? Most probably one cannot reckon with such a rapid growth of the body mass in cave bear cubs. The female could hardly breed two or even three such big cubs during the first half-year when their diet was predominantly milk. It is more probable that the cubs had distinctly large jaws. Therefore, the jaws/body ratio must have been essentially higher than in adult cave bears, and larg- er than in brown bear cubs. Confirmation of this supposition is found in the only extant precisely described and measured skeleton of an approximately seven-month- old cave bear cub (finds of this kind are extremely rare!). The author of the article, Ehrenberg (1964, 243-244), was surprised to discover that the facial part of the skull was much larger than one would expect with regard to the cranium, short trunk and weak thorax. The reconstruction revealed that at a total length of 60 cm and height of 30cm more than one third was occupied by the head (Ehrenberg, 1964, 223). It seems that the most probable reason for such a "disproportion" was the func- tional development of dentition that must have been as fast as with the present-day brown bear During this process the jawbone size was consequently adapted to the growing dentition. 2. Cave bear males have on the average larger teeth than females. This holds espe- cially for the canines, according to the size of which the sex can be determined (Koby, 1949; Kurtén, 1955). In cubs the wide crown base and its growing root occupy a very large part of the jawbones. It is clear in x-ray photographs that the height and thickness of the mandible body at a particular age clearly depend pre- cisely on the size of the canines. Numerous specimens from the Divje babe indicate that in the same ontogenetic phase the mandibles of females are smaller and more gracile than those of males. Accordingly, it could be inferred that sexual dimorphism in cave bear mandibles was already manifested during the first year of life. We must also consider another possibility: that the development of permanent dentition in males lagged behind that in females. However, if such differences existed at all, they could have not been essential for the above-mentioned reason: the young must get their permanent teeth in place at a certain age to be able to feed properly. Also in pre- sent-day bears no important differences between the sexes were observed in the process of teeth growth during the first year (Dittrich, 1960; Marks&Erickson, 1966, 393). At least one example will represent the upper dentition: 7. (PI. 7, figs. 1-3) - The premaxilla and maxilla of a male approximately 6.5-7.5 months old: both bones are not fused at this particular age. In present-day bears they become inseparable in adult animals - after the 4th year (Marks & Erickson, 1966, 398-400). The М^ crown shows the first signs of wear According to the shape of the alveola, P"^ must have been just in the eruption phase; most of the crown probably already protruded out of the jawbone. Of the incisors only I^ is preserved. Shortly before the cub died it had probably already pierced the gum with the tip of its crown. The tooth socket of the I^ root is not damaged, which permits the observation on the completed eruption of the tooth. By contrast, the narrow aperture of the I^ alveolus proves that the eruption of this incisive had not yet started. Above this alveolus the shallow alveolus of the deciduous di^ is also preserved; at that age the tooth was still Ontogenetic development of dentition in the cave bear_ 27 in the gum, but v^^ould have dropped out of the gum in a month or so. The upper canine is hidden in the maxilla. In the x-ray photograph (PI. 7, fig. 3) it can be seen that its root had not yet started to form. The crown is hollow and is still situated much below, or better, above the rim of the upper jawbone. The deep root socket of the deciduous eye-tooth is entirely preserved and separated completely by a solid bone wall from the developing crown of the permanent canine. Therefore we presume that the root of the deciduous canine in this phase of the ontogenetic development still did not display signs of contact resorption. Before we end the description of ontogenetic development in the seventh and eighth months of life, another curiosity should be mentioned: Among the juvenile jawbones from the Divje babe I, most specimens belong precisely to the age period being discussed, although according to other researchers (Ehrenberg, 1931, 1964; Kurtén, 1958, 1976) the remains of 7-month-old cubs that died in the middle of summer must have been a real rarity. The general conviction of the last few decades is that the massively preserved remains of the cave bear in typical Pleistocene cave sites are of animals that died of exhaustion during long hibernation - in winter and mostly just before spring. However, also the analysis of isolated d^ and М^ teeth (Debeljak, 1996a, 1997) indicated that a remarkably high proportion of the fossil population belongs to cubs that perished presumably at an age of 6-8 months, between July and September. The Divje babe as a typical cave bear site does not represent any excep- tion. Such results about the age structure of the fossil population are therefore sur- prising and unexpected. We could explain them in two different ways: a) Our age estimates of the individual jawbones (and consequently also of isolated juvenile teeth) are not correct, and the most frequent age group of 7-month-old ani- mals actually represents those cubs that died during their second hibernation. In this case, the ontogenetic development of cave bear dentition should lag as much as 6 months behind the ontogenetic development that was ascertained for present-day bears. According to the feeding habits and needs in the first year (that were described before), this seems to be almost impossible. On the other hand, in favour of the suppo- sition above, the appearance of the first thin cementum deposit on the М^ root of the 7-month-old cave bear cubs could be mentioned. This cementum layer was explained as the "neonatal zone" (Debeljak, 1996a, 29-30, PI. 26-28), but it is very similar to the following "winter" increments. b) The other possible interpretation of the discordance between the expected and observed mortality profile is that our age estimates are correct. Life habits and the mortality of the cave bear are then different than was thought so far. (Similarly, Musil (1965, 74-76), after measuring long bones of extremities, came to the conclu- sion that cave bears kept visiting the cave Pod hradem and also died there in the sum- mer months.) Perhaps the final answer will be given by further researches into the ontogenetic development in present-day bears from different environments, and by detailed analyses of the dental cementum in bear cubs. From the ninth month to the end of the first year During the 9th or 10th month the bears finally get the second lower Mg molars. The last upper М^ molars start erupting in the ninth month. Sometimes after only the tenth month the permanent canines begin to pierce through the jawbone. Shortly 26_v Irena Debeljak before the completed first year (11th or 12th month) the Mg teeth also appear through the gum. Owing to the inclined position and remarkably flat crown much time is needed before they become erupted entirely. Ehrenberg (1931, Pl. 120, fig. 6) published a photograph of a mandible of a cave bear cub to which an age of approximately 8-9 months could be ascribed. Plate 8, fig. 1 and plate 10, fig. 1 show the lower jawbone of an approximately 10- month-old present-day brown bear from Slovenia. The anterior part of the Mg is "out". The tips of the permanent canines have just appeared out of the alveola, but have not yet penetrated the gum. Lateral-distal from them the deciduous canines are attached. All the other milk teeth were shed before the tenth month. The mandible in plate 9, fig. 1 and plate 10, fig. 2 belonged to an approximately one-year-old brown bear from the Kočevje region (S Slovenia). Somewhat more than 1 cm of the canine reaches above the rim of the mandible. Beside it the deciduous canine with a worn out crown and strongly resorbed root is still in place. For a certain period during replacement of their canines the bears have the permanent and the deciduous canines in their gums at the same time. The deciduous canines are shed at an age of 12-15 months only, during hibernation in the den. The above two examples of brown bear mandibles are shown here owing to the lack of an appropriate mandible for the age period being considered in the collection from the Divje babe. A well-defined gap was observed among isolated teeth (М^) as well. It appears that the Divje babe I site contains scarcely any remains of cave bears that died between the 10th month and the completed first year of life, i.e. during the first part of wintering in the cave den (Debeljak, 1996 a, 1997). However, with regard to the previous discussion, it is also possible that this "miss- ing" age-group represents the juveniles of the next summer period. From one year to one and a half years In bears, during the period between one year and one and a half years the eruption process of permanent dentition comes to an end. The individual differences become more pronounced (Dittrich, 1960), thus the age determinations are less accurate than for the previous period. The last permanent teeth (М^, Mg and canines) are usu- ally completely erupted in the present-day bears of one and a half years old. This period of ontogenetic development in the cave bear is represented by the fol- lowing three examples. Their individual ages were estimated according to the data for present-day brown bears. Nevertheless, we should also consider the other possi- bility of slower ontogenetic development of dentition in the cave bear. In this case, the next three mandibles could belong to two-year-olds or even older cubs that died during their third winter. 8. (PI. 11, figs. 1, 2; PI. 13, fig. 1) - The mandible of a male approximately 12-15 months old: The mandible size was equal to that of the adult present-day brown bear. The symphyseal part, where the left and right mandibles were joined, is most proba- bly pathologically deformed. The inflammatory alteration was possibly the result of a traumatic lesion of the jaw. About a centimeter and a half of the canine crown pro- trudes out of the alveolus, and more than half of the root wall is formed already. The anterior part of the chewing surface of Mg is slightly worn out. A large part of the Mg crown had not yet erupted through the gum. Its position is still inclined with respect to the tooth row. Ontogenetic development of dentition in the cave bear_ 29 During the eruption of the last lower M3 molar it sometimes happened that its crown became wedged with the adjacent Mg crown. On some adult cave bear mandibles corresponding pathologic changes can be observed that most certainly caused serious troubles to the animals. According to certain authors the irregularities in eruption of the last molars were the main, or at least a very important cause of mortality in cubs during their second winter (Ehrenberg, 1931; Abel, 1931). The investigations at the Divje babe, however, did not confirm this assumption. I believe that the difficulties mentioned could have seriously endangered cave bears mostly later in their lives. Although it was also possible that the eventual infection in a weakened cub sometimes terminated even with its death. 9. (PL 12, figs. 1, 2; PI. 13, fig. 2) - The mandible of a female about 15 months old: Two thirds of the canine root are already formed. The crown has not yet erupted entirely. It extends for more than two centimeters beyond the margin of the alveolus. Mg is not yet "in place" or in the occlusal plane. The P^ and Mg roots are still open at the ends. The root canal of М^ is sealed and the crown "polished", with individual, 2-3 mm wide attrition facets. Wear is also evident on the anterior part of Mg. On the chewing surface of Mg, however, no traces of wear are visible. Owing to lack of space in the tooth row the individual teeth pressed one against the other (After the first year the facets started appearing at points of contact between certain teeth, and they widened and deepened with time. This is especially pronounced on the anterior wall of the Mg crown, and the posterior wall of the M^^ crown. This t5фe of wear is called approximal wear, in contrast to occlusal wear on the chewing surface). For comparison the mandible of the nearly one-and-a-half-year-old brown bear from the surroundings of Kočevje can be taken (PI. 16, figs. 1, 2; PI. 18, fig. 1). Here, too, the canines are not yet entirely erupted. However, the tooth roots are already closed, with the exception of the Mg and canines. The Mg crown has not yet fully emerged from the gums. The following individual is also in a similar ontogenetic phase: 10. (PI. 14, figs, 1, 2; PI. 15, figs. 1-3) - The mandible of a female cave bear approx- imately one and a half years old: The canine is somewhat more developed than in the brown bear just discussed. Its crown is practically entirely erupted, only about one centimeter of the root is lacking. The Mg is in place in dentition. The М^ is somewhat more worn out as in the above-discussed specimens. The surface is smoothened and covered with small wear facets. At the point of contact of М^ and Mg a well developed facet appeared on both teeth (approximal wear). On the posterior wall of the М^ crown this facet is more than 4 mm wide. The М^ root (tooth canal) has already closed during the first year. At the age of around one and a half years its wall was about 2.5-2.75 mm thick. At the Mg the tips of the root were still somewhat perforated. The Mg root is still widely open, and its wall is very brittle (PL 15, fig. 3). Isolated teeth have usually been defined as juvenile if the root is open, or as adult if the root is closed. In this way, certain teeth of the same individual are determined as adult, and others that lag behind in development as juvenile. The problem, however, is not only in the uncertainty of the data. The classification mentioned is inadequate first of all because a large proportion of cub teeth are incorrectly attributed to adults. The bear becomes adult around the fourth year only. The М^ root closes before the end of the first year, and the Mg and P^ at an age of one and a half years. Therefore, the closure of the root apices (or pulp canals) can be a criterion for determining adult sta- tus only in the last, most distal molars and canines. As co-author I am obliged to call attention to an error in a paper from five years 28_v Irena Debeljak ago, when the ontogenetic development of dentition in bears was not yet sufficiently known to us (Turk et al., 1992). In that contribution the measurements of "adult" М^ molars were statistically analyzed with the aim of establishing the ratio of the two sexes in the adult population of cave bears. In fact, however, the teeth examined should be attributed to older juveniles (two years, three years, possibly at most four years old). Their root was closed, and on the ground of this criterion we wrongly attributed them to adults. Further development of dentition and jawbones: Presumably in the middle or at the end of the second year of life the cave bears already had the complete permanent dentition erupted. Nevertheless the teeth con- tinued their development. The originally hollow roots and crowns became more and more filled with dentine. Finally, in the center only a narrow canal and the pulp cavity at the passage from root to crown were left. We assume that in the cave bear during the 4th year the last tooth roots also became sealed: those of the М^, Mg and of canines. The initially explosive growth of jaws in the following years gradually slowed down. 11. (PI. 17, figs. 1, 2; PI. 18, fig. 2) - The mandible of a subadult male about 4 years old: The age of this specimen was determined by counting the growth lines (i.e. incre- ments) in dental cementum. The method is regarded as the most objective, and it is generally used for estimating the individual ages of wild animals (more in: Debeljak, 1996a, b). The above-mentioned process of dentine deposition in the interior of the teeth is already at an advanced stage, as clearly seen in the x-ray photograph (PI. 18, fig. 2). The М^ crown is the most worn out (especially the protoconid and hypoconid), Mg less and Mg very little so (PI. 17, fig. 2). At the contact of individual molars rela- tively deep facets developed. On the posterior wall of the М^ crown such a facet is already more than 6 mm wide. The length of the crown in this way could not be exactly measured any more. According to the x-ray picture the canine and Mg roots are not yet completely closed, although they are near to it. In present-day bears the canine root becomes closed around the 4th year (Marks & Erickson, 1966, 395, 397), i.e. during the time when they reach adulthood. The above described mandible had not yet reached its final size. The mandibles of fully grown males measure 5-10 cm more in length. The growth of jaws therefore also continued after the fourth year. In the present-day black bear the head of males grows during the first 8 years, while in females the growth is terminated somewhat earlier, soon after reaching sexual maturity (Marks & Erickson, 1966, 400-402). Most probably it was not much different in cave bears either. Conclusion In this contribution the ontogenetic development of dentition in the cave bear, and bears in general, was presented. The process of replacement of deciduous dentition and the eruption of permanent teeth is generally completed by the age of one and a half years. Until then the particular ontogenetic phases are a good indicator of indi- vidual age. On the basis of the cases described and the data collected the age of juvenile cave Ontogenetic development of dentition in the cave bear_ 31 bear jawbones can be quite accurately estimated. In the future the ontogenetic devel- opment and the criteria for determining the individual age of particular (isolated) teeth that are the most numerous and most informative fossil remains of the cave bear will have to be presented in detail. Here are the principal conclusions: - The process of tooth growth and of the replacement of deciduous dentition with the permanent type took place in the cave bear in the same way, through the same and probably also synchronic ontogenetic phases as in the related present-day bears. - It is possible to infer that a certain ontogenetic phase of dentition development corresponds to approximately the same age of an individual in the cave bear, as well as in the brown bear The development of dentition in the cave bear must not have significantly lagged behind, since cubs at a certain age (in the 6th or at least in the 7th month of life) needed the first pair of permanent molars (М^ & М^) to be able to start chewing hard plant food. - This argument speaks against another possibility, that the ontogenetic develop- ment of cave bear dentition was in fact esentially slower than in present-day bears. Such a characteristic would (in certain circumstances) endanger the existence of the species. Nevertheless, this alternative still cannot and should not be simply rejected. - The size of the jawbones during the first year of life (and also later) was depen- dent upon the sizes of permanent teeth that were developing during that time, partly encased in the jawbones and almost completely filling them up. - The growth of jawbones in cave bear cubs was essentially faster than in the pre- sent-day brown bear. Already at the age of one year their mandible was of the same size as in the adult brown bear This most certainly does not mean that the rest of the body was also larger to the same degree. - It is presumed that in the cave bear the secondary sexual dimorphism was mani- fested already in the first year of life; males had larger sized jaws than females. - The generally used criterion of distinguishing teeth as juvenile if their crown is open, and adult when it is closed, is not adequate for most of the cave bear teeth. The bear becomes adult at the age of around four years. The М^ root, however, closes as early as the first year of life (after the 8th month), most of other teeth by the age of one and a half years, and only the roots of М^, Mg and canines at about four years. - In the study of juvenile jawbones from the Divje babe I site the fact cannot be overlooked that the majority of the specimens originally belonged to presumably about seven-month-old cubs that therefore died in the middle of summer. This is in contradiction with the prevailing opinion that massive remains in typical cave bear localities are of animals that perished owing to exhaustion during hibernation, prior to spring. - An interesting problem and task for the future will be to prove and explain this statement with further researches and additional data. Acknowledgements I am much obliged to Ivan Turk, the leader of excavations at the Divje babe I, for the material he ceded for examination. The excavation has been carried out by the Institute for Archaeology at the Scientific Research Centre of the Slovenian Academy of Sciences and Arts. At the Clinic for surgery and small animals of the Veterinary Faculty in Ljubljana, the x-ray examination of jawbones of the cave and brown bear 30_v Irena Debeljak was kindly allowed, and performed professionally thanks to the efforts of the veteri- narians Teodora Ivanuša, Janez Štubelj and Gregor Frelih. Andrej Bidovec (Veteri- nary Faculty, University in Ljubljana) and Ciril Štrumbelj (Breeding and hunting ground "Medved", transi. "Bear", Kočevje) provided skulls of present-day brown bear cubs from Slovenia that were necessary for comparisons. Vida Pohar reviewed the manuscript. All others who were of whatever assistance in the elaboration of this paper are also warmly thanked. Ontogenetski razvoj zobovja pri jamskem medvedu Uvod Za razliko od filogenetskega razvoja ontogenetski razvoj zobovja jamskega med- veda do zdaj še ni bil pregledno in nazorno opisan in je v strokovni javnosti na sploš- no slabo poznan. Večina raziskovalcev jamskega medveda se omeji le na podatek, da je neka čelju- stnica juvenilna, oz. da je pripadala mladiču. Le redki avtorji (kot npr. Rädulescu & Samson, 1959) fotografije ali opise opremijo z natančnejšim podatkom o starosti mladiča, ki jo lahko ocenimo s pomočjo primerjave z današnjim rjavim medvedom. Tokrat so o izraščanju zobovja rjavega medveda zbrani vsi tisti podatki, ki so pomem- bni za ugotavljanje individualne starosti čeljustnic mladičev jamskega medveda in tudi drugih medvedjih vrst. Pri tem ne gre samo za to, da bi ob razmeroma redkih najdbah juvenilnih čeljust- nic določali starost že davno poginulih živali zgolj iz radovednosti, kot nekakšno za- nimivost. Paleontologe in arheologe zanima tudi vedenje jamskih medvedov in okolje, v katerem so živeli, predvsem pa odnos med pračlovekom in medvedom. S tega stališ- ča nam natančna ocena individualne starosti čeljustnic manj kot leto dni starih mla- dičev ponuja zelo pomemben podatek: to je sezono, ko so živali poginile. Seveda nam najbolj natančne podatke o mortaliteti jamskega medveda omogoča starostna analiza posamičnih, izoliranih zob; v tistih paleolitskih jamskih najdiščih, ki so bili hkrati tipični brlogi jamskega medveda, jih najdemo v desettisočih primerk- ih. Vendar, individualno starost posamičnih juvenilnih zob lahko pravilno ugotovimo le, če njihov razvoj oziroma stopnjo formiranosti pri različni starosti najprej preuči- mo na nizu celih čeljustnic. Ravno to je bil povod za analizo čeljustnic mladičev jamskega medveda iz pale- olitskega najdišča Divje babe I. Ta študija je služila kot osnova za nadaljnjo raziskavo starostne sestave populacije jamskega medveda iz zgornjega dela pleistocenskih sedi- mentov (Debeljak, 1996 a, 1997). Starostno analizo smo izpeljali na izoliranih mleč- nih zobeh d^ in stalnih zobeh М^, zato je v tem prispevku najbolj podrobno predstav- ljen prav njun ontogenetski razvoj. Ontogenetski razvoj zobovja pri jamskem medvedu _^ Dosedanje raziskave Ontogenetski razvoj pri jamskem medvedu je prvi preučeval Ehrenberg. Ugo- tovil je, da so stopnje ontogenetskega razvoja zobovja prav takšne kot pri rjavem medvedu (1931, 640). Opisal je posamezne razvojne stopnje spodnjih čeljustnic in pri- bližno ocenil njihovo individualno starost (1931, 659-675, 701-703). V tistem času so bili na voljo le skopi podatki o rasti zobovja pri rjavem medvedu, zato je razumljivo, da so bile Ehrenbergove ocene starosti nenatančne. Sklenil je, da v znanem naha- jališču Drachenhöhle pri Mixnitzu veliko ostankov pripada mladičem, ki so poginili od izčrpanosti, stari manj kot 4 mesece, tik pred nastopom pomladi. Tej skupini naj bi sledila izrazita vrzel in potem najštevilčnejši ostanki približno enoletnih mladičev. Višek smrtnosti pri tej starosti naj bi bil posledica težav pri izraščanju zadnjih kočni- kov. Po domnevni odsotnosti ostankov 4- do 10-mesečnih mladičev je Ehrenberg sklepal, da je jamski medved uporabljal jamo le pozimi, v času hibernacije. Takšno mnenje je med raziskovalci prevladovalo vse do danes. Nekdanje spektakularne pred- stave o lovu na jamskega medveda so se umaknile trezni znanstveni presoji. Čez 301etjeEhrenbergže imel dobre primerjalne podatke za recentnega rjavega medveda, in je skoraj popolnemu skeletu mladiča jamskega medveda iz Hartlesgrabna pripisal starost 7 mesecev (1964, 217-219). V istem prispevku je popravil ocene starosti nekaterih mandibul iz leta 1931. Še vedno pa je vztrajal pri svojem prepričanju, da v starostni sestavi ostankov jamskega medveda obstaja omenjena časovna vrzel, in da so redki ostanki 4-10-mesečnih mladičev zgolj izjema, ki potrjuje to pravilo. Musil (1965, 72) je juvenilne čeljustnice jamskega medveda iz jame Pod hradem razvrstil po napredovalem ontogenetskem razvoju in jih podrobno opisal. Ni pa jim natančneje določil individualne starosti. Material in metode Ontogenetski razvoj zobovja pri jamskem medvedu bo v nadaljevanju opisan na enajstih primerih čeljustnic iz paleolitskega najdišča Divje babe I. Jama leži pod ro- bom Šebreljske planote, nad dolino Idrijce (W Slovenija). Večidel pleistocenskih jam- skih sedimentov izvira iz obdobja srednjega würma. Vse fosilne ostanke jamskega medveda iz Divjih bab hrani Narodni muzej Slovenije v Ljubljani. Splošne podatke o najdišču najdemo v naslednjih delih: Turks sodelavci, 1989a, b in Turk ed., 1997. Pri oceni starosti posameznih čeljustnic sem si pomagala z izčrpnimi Dittrich- ovimi (1960) podatki za recentne medvede in s primerjavo juvenilnih čeljustnic rja- vega medveda iz Slovenije. Spol sem določila po velikosti zob, predvsem kaninov, gle- de na ugotovitve Kobyj a (1949) inKurténa (1955). Nekatera dejstva o življenjskih navadah rjavega medveda, ki jih lahko pripišemo tudi sorodniku jamskemu medvedu, sem povzela po naslednjih delih: Macdonald ed., 1985, 88-95 (slovenski prevod istega dela: Macdonald ed., 1996) in Kryštuf ek, 1991, 191-193. Čeljustnice in zobje jamskega medveda - splošno Spodnjo čeljust medvedov sestavljata dve spodnječeljustnični kosti (mandibuli). Spredaj se stikata v posebni zrasti (simfizi), ki nikoli ne okosteni. Zgornjo čeljust na 32_v Irena Debeljak vsaki strani oblikujeta dve parni kosti: medčeljustnica, ki nosi sekalce in sega do podočnika ter zgornja čeljustnica ali maksila. Ti dve kosti sta koščeno zraščeni samo pri odraslih medvedih. V čeljustnicah so oblikovane zobnice ali alveole, v katerih tičijo zobne korenine. Tako rjavi kot tudi jamski medved imata v obeh čeljustih na vsaki strani naslednje mlečne zobe: po 3 sekalce ali incizive (dil-3), 1 podočnik ali kanin (dc) in ponavadi 3 ličnike ali premolarje (d2-4 oz. p2-4). Na vsaki strani spodnje čeljusti jamskega medveda so naslednji stalni zobje: trije incizivi (I^.g), kanin (C), ponavadi samo en premolar (Р^) in trije meljaki ali molarji (M^ g). V zgornji čeljusti je en molar manj. Kočniki imajo široko žvekalno površino z nizkimi, zaokroženimi grbinicami. Že zgodnje raziskave morfologije zobovja in lobanje so pokazale, da so bili jamski medvedi predvsem rastlinojedi (cf. Kurtén, 1976). Sodobne izotopske analize so to domnevo potrdile (B o cher en s et al., 1994). Stalno zobovje medvedov je podrobno opisal Rode (1935). Ko by (1952) in Rädu- lescu in Samson (1959) pa so opisali mlečno zobovje jamskega medveda. Pri orientaciji čeljustnic in zob so v rabi različni izrazi. V tem prispevku se srečamo z naslednjimi: Spredaj - anteriorno - mezialno. Zadaj - posteriomo - distal- no. (Poenostavljeno! Vsi našteti izrazi sicer niso ekvivalentni.) Proti licu - bukalno - lateralno. Proti jeziku - lingvalno (pri mandibuli) oziroma palatinalno (pri maksili). Grizna (zgornja) površina zob je okluzalna. Ontogenetski razvoj zobovja pri medvedih (družina Ursidae) Nekaj podatkov o izraščanju stalnih zob pri recentnih medvedih najdemo v naslednjih delih: Pohle, 1923; Couturier, 1954; Rausch, 1961; Marks in Erickson, 1966. Najbolj natančno pa je razvoj mlečnega zobovja in zamenjavo s stalnimi zobmi pri rjavem medvedu raziskal Dittrich (1960). Ugotovil je, da je ta proces enak in sočasen tudi pri drugih vrstah medvedov. Zaporedje izraščanja posameznih zob iz dlesni je predstavljeno na sliki 1. Druge Dittrichove podatke o ontogenetskem razvoju zobovja pri medvedih lahko strnemo v naslednje bistvene ugotovitve: Mladiči se skotijo brez zob. Prvi mlečni zobje začnejo izraščati v drugem mesecu življenja in so v tretjem mesecu na svojem mestu. Prvi stalni kočniki začnejo prodirati skozi diesen v petem mesecu življenja. Šele potem ko zraste prvi par stalnih molarjev (М^&М^), lahko mladiči žvečijo trdo hrano. Mlečno zobovje pri tem nima skorajda nobenega funkcionalnega pomena. Mlečni zobje izpadejo do konca 15. meseca. Zadnji stalni zobje dokončno izrastejo pri povprečni starosti okoli enega leta in pol. Dittrich (1960, 119-123) je ugotovil, da prehranjenost (telesna teža) pri medve- dih navadno ne vpliva na razvoj in hitrost izraščanja zobovja. Tudi individualne raz- like so pri tem procesu razmeroma majhne (glej si. 1). Razporeditev mlečnih in stalnih zob v čeljustih mladiča rjavega medveda pona- zarjata sliki 2a in 2b. Ontogenetski razvoj zobovja pri jamskem medvedu _^ Ontogenetski razvoj zobovja pri jamskem medvedu Prvi trije meseci Kostni ostanki še nerojenih živali (fetusov) in tistih mladičkov, ki so poginili ob rojstvu ali kmalu zatem (neonati), so se v pleistocenskih najdiščih ohranili le izjemo- ma. Tovrstne najdbe v Divjih babah pa kljub temu niti niso tako redke, saj je jama kot brlog skoz dolga tisočletja služila predvsem samicam jamskega medveda, ki so tu v zimskih mesecih, od decembra do februarja kotile mladiče (Turk et al., 1989b; Debeljak, 1997). Drobne in zaradi poroznosti krhke spodnje čeljustnice še neroje- nih ali novorojenih medvedkov so dolge 2-3 centimetre, široke pa le okoli 5 milime- trov. Mladiči jamskega medveda so se skotili brez zob. Tako je tudi pri današnjih medvedih. Že v prvem tednu življenja pa najdemo v preparatih čeljusti rjavega medveda zametke mlečnih zob: majhne, votle vršičke kron, ki še niso prodrli iz dlesni (Dittrich, 1960, 11, si. 1, 2). To fazo ontogenetskega razvoja predstavlja naslednji primer: 1. (Tab. 1, si. 1, 2) - Leva in desna mandíbula dveh neonatov, ki sta poginila že v prvih dneh po rojstvu: Zaradi nazornosti sta mandibuli na sliki združeni v naravni legi, čeprav ne izvirata od istega osebka. Od strani vidimo (tab. 1, si. 2), da je telo mandibule polkrožno upognjeno, kar je značilno za neonate. Na polomljeni zgornji površini se lepo vidita zametka obeh mlečnih kaninov in celo zametek protokonida zadnjega mlečnega zoba d^ oz. p^, kot ga nekateri označujejo. (Protokonid je osrednja, največja grbinica na omenjenem zobu). Zametki mlečnih zob so bili prvotno zaprti v kosti. V tistem času so se alveole, skozi katere bi kasneje prodrli rastoči mlečni zobje, šele oblikovale. Dolžina opisane mandibule je znašala okoli 4 centimetre; toliko, kot pri novorojenih mladičih rjavega medveda. Ehrenberg (1973) je dokumentiral najdbo skoraj popolnega skeleta neonata, starega približno 10 dni iz avstrijskega nahajališča Salzofenhöhle. Po različnih izme- rah in rekonstrukciji, ki so jo naredili iz kosti, je ugotovil, da so bili mladiči jamskega medveda ob rojstvu morda le malenkostno večji kot pri rjavem medvedu. V leglu rjavega medveda so običajno dva do trije kot podgane veliki mladiči, ki tehtajo le 350-400 gramov. So goli, slepi in popolnoma nemočni. Sami še ne morejo vzdrževati svoje telesne temperature. Preživijo lahko le ob skrbni materi, v pred mrazom zavaro- vanem okolju brloga. Drugi in tretji mesec življenja so tudi mladiči jamskega medveda zagotovo preživeli v brlogu oziroma jami. Samica jih ni zapuščala. V dolgih mesecih do nastopa pomladi je živela le od maščobne zaloge, ki si jo je nabrala pozno poleti in jeseni. Za njene mladiče je bil to čas dojenja; izključno mlečne prehrane. Medtem so vsi mlečni zobje postopoma izrasli iz dlesni. Pod njimi, skrite v kosti, pa so se oblikovale in krepile krone stalnih zob. Zaporedje izraščanja posameznih mlečnih zob lahko rekon- struiramo s pomočjo podatkov za rjavega medveda (si. 1). To obdobje ontogenetskega razvoja predstavljata naslednja dva primera: 2. (Tab. 2, si. 1-3) - Mandíbula mladiča, starega okoli 2 do 2,5 meseca: Krona prve- ga stalnega molarja М^ je že izobhkovana; na rentgenskem posnetku (tab. 2, si. 2, 3) se lepo vidi kot tanka, votla lupina, ki je zaprta v čeljustnici. Rasti so začeli tudi prvi milimetri stene korenine. V notranjosti mandibule tičita vršička oziroma zametka kron P4 in C. Stalni zobje so se razvijali v votlih delih mandibule, med katerimi so tanki prekati. Na zgornji strani čeljustnice, na mestu, kjer bi kasneje izrastel М^, zeva 34_v Irena Debeljak ozka reža. Pred njo so luknjice; to so alveole, v katerih so tičale korenine mlečnih pre- molarjev d^ in dg. Dokazujejo nam, da sta omenjena mlečna zoba že izrastla iz čelju- stnice, torej mladič po vsej verjetnosti ni bil mlajši od dveh mesecev. Mandíbula je bila približno tako dolga kot pri približno štiri mesece starem rjavem medvedu (si. 2a), vendar precej bolj robustna. 3. (Tab. 3, si. 1-3) - Obe polovici mandibule mladiča, starega okoli 2,5 do 3 mesece: Brazda na mestu, kjer bi čez mesec ali dva začel izraščati М^, se je že razširila. Z zgornje strani se skoznjo vidi temna, kot jajčna lupina krhka krona М^. Oblikovala se je že zgornja četrtina korenine М^ (tab. 3, si. 2, 3), ki pa je tanka kot papir. Tudi krone stalnih incizivov in zametki C in P^ so zaprti v čeljustnici. Na zgornji strani mandi- bule se lepo razločijo alveole mlečnih zob. Pri tej starosti so ravnokar izrastli skoraj- da vsi mlečni zobje, vendar se tu niso ohranili. (Proces izraščanja mlečnih zob lahko ponazorimo s primerom d4: Pri starosti 1 do 2 meseca je bila v čeljusti zaprta krona d^ temno rjave barve, motna in zelo krhka. Kasneje se je svetleje obarvala najprej konica protokonida, to je konica, ki prva prodre skozi diesen, in potem postopoma še pre- ostali del krone. Pri 2- do 3-mesečnih mladičih je bila krona izraščenega d^ že okre- pljena, normalno svetla in sklenina je dobila značilen sijaj. Korenina pa je bila še vedno votla, in zato precej krhka.) Zgoraj opisana mandíbula je tako velika kot pri polletnem rjavem medvedu. Za primerjavo nam lahko služi skica bistveno manjše mandibule trimesečnega recentne- ga rjavega medveda, ki jo je objavil Pohle, 1923. Četrti do šesti mesec življenja V četrtem mesecu imajo medvedje že vse mlečne zobe. Bolj ali manj formirane krone stalnih zob pa so medtem zaprte v čeljustnicah in se postopoma krepijo. Tako je na primer pri štirimesečnem mladiču pod mlečnim zobom d^ že oblikovana krona stalnega P4 (si. 2a, 2b). Z nadaljnjo rastjo korenine začne stalni zob izpodrivati mlečnega. Močan protokonid krone P4 se pri tem zagozdi med oba kraka korenine d4 in sčasoma inducira kontaktno resorbcijo le-te. Podobno se zgodi tudi pri zgornjem paru mlečnega d^ in stalnega P^. V petem mesecu začnejo pri medvedih izraščati prvi stalni kočniki (Ml). Najprej pokuka iz dlesni sprednji del zoba М^ s protokonidom in parakonidom, kmalu zatem pa še zadnji del krone z metakonidom in talonidom (Dittrich, 1960, 80-81). Na pravkar opisani razvojni stopnji je zobovje mladiča rjavega medveda na sliki 2a. Couturier (1954, 142-143) je objavil to rentgensko sliko ujetega mladiča in mu prisodil starost treh mesecev. Po Dittrichovih (1960) podatkih pa je očitno, da je bil mladič v resnici starejši; imel je vsaj 4 mesece. Rädulescu in Samson (1959, 211, si. 11) sta objavila fotografijo mandibule približno 4-mesečnega jamskega medveda. Musil (1965, 72, tab. 3, si. 10) je pred- stavil primerek mandibule, ki je morda nekoliko mlajši. Slike čeljustnice jamskega medveda, ki bi bila tipična za petmesečnega mladiča (М^ ali М^ v fazi izraščanja) pa v strokovni literaturi še nisem zasledila. V osteološki zbirki iz najdišča Divje babe I nimamo nobene za objavo primerne čeljustnice 4 do 5 mesecev starega mladiča. To pravzaprav ni naključje, saj tudi med sicer izredno številnimi izoliranimi mlečnimi zobmi najdemo le redke primerke, ki bi jih lahko uvrstili v to starostno skupino. (Takšni so na primer zgornji ali spodnji d4 z okrepljeno korenino, ki je na konceh že nekoliko resorbirana. Posamezne konice na Ontogenetski razvoj zobovja pri jamskem medvedu _^ kroni so zaobljene in pogosto nosijo drobne obrabne fasete. Debeljak, 1996 a, 1997). Očitno je bila smrtnost štiri- do petmesečnih mladičev v jami Divje babe precej nižja kot v mlajših starostnih razredih. Namen tokratnega prispevka ni razpravljati o možnih vzrokih različne stopnje smrtnosti med letom. Omenim naj le, da je bil četrti do šesti mesec življenja čas nastopa pomladi. Pri rjavem medvedu mladiči s samico zapustijo brlog po dopolnjen- em tretjem mesecu; aprila ali maja, včasih šele v začetku junija. Verjetno je bilo tako tudi pri jamskem medvedu. Poleg mleka, ki ga sesajo pri materi, začnejo medvedje v petem ali šestem mesecu gristi trdno hrano. To je mogoče šele takrat, ko zraste prvi par stalnih molarjev (Dittrich, 1960, 14-15). Zgolj z majhnimi, koničastimi mlečnimi zobki si pri žveče- nju ne bi mogli kaj prida pomagati. Šele z novimi kočniki pridobijo potrebno žvekal- no površino. Sedmi in osmi mesec življenja Mladiči so dočakali poletje. Za vso medvedjo družino je prišel čas intenzivnega prehranjevanja. V naslednjih mesecih so morali pridobiti zadostno plast maščevja, če so hoteli preživeti stradanje med naslednjo zimo. Zobje 6- do 8-mesečnih mladičev so bili takrat v naslednjem stanju: 4. (Tab. 4, si. 1-5) - Mandíbula samice, stare okoli 6-7 mesecev: Razvoj je v primer- javi s prejšnjim primerkom (tab. 3) precej napredoval. Krone vseh stalnih zob so že oblikovane. Kasneje ne bi več rastle, ampak bi se le še okrepile, s tem da bi se notran- jost postopoma zapolnila z zobovino oz. dentinom. М^ je bil pri tem mladiču že kak mesec na "svojem mestu" v čeljusti in ima razvite več kot 4/5 korenine. Krona se je nekoliko okrepila, korenina pa je še povsem votla in odprta na apeksih (tab. 4, si. 5). Na Mj so očitni prvi znaki obrabe, kar kaže, da je medvedek že nekaj časa grizel trdo hrano. Pri žvečenju so nastale številne drobne obrabne fasete z značilno svetlečo, zglajeno površino. Na fotografijah in rentgenskem posnetku se lepo vidi, kako onto- genetski razvoj pri posameznih zobeh različno napreduje; v skladu s podatki za rjave- ga medveda, podanimi na si. 1. М^ v razvoju prehiteva druge stalne zobe. Sledi mu ki je bil v tem času že izraščen, vendar se ni ohranil. Ц je prodrl skoz diesen malo pre- den je mladič poginil, P^ in Mg pa sta bila tik na tem. Vršička njunih kron sta se že svetleje obarvala. Zadnji sekalec Ig je še vedno zaprt v mandibuli in ga vidimo le na rentgenski sliki. Prav tako podočnik, ki ima oblikovano samo krono, korenine pa še ne. P4 je v tem starostnem obdobju izpodrival mlečna zoba d^ in dg iz čeljusti. Njuna korenina je bila takrat že močno resorbirana. Najkasneje čez kakšen mesec bi d4 (pri našem primerku se ni ohranil) s popolnoma resorbirano korenino po naravni poti izpadel iz dlesni. (Zadnji mlečni premolar d^ je pri medvedih v rabi zelo kratek čas; pri žvečenju trdne hrane sodeluje le okoli 3 mesece, zato njegova žvekalna površina praviloma nikoli ni močno obrušena.) Velikost zgoraj opisane mandibule ustreza leto dni staremu mladiču rjavega medveda (tab. 9, si. 1; tab. 10, si. 2). Ali so naše ocene starosti pravilne? Je bil razvoj zobovja pri jamskem medvedu hitrejši, ali pa je morda zaostajal v primerjavi z rjavim medvedom? Razmislimo o tej možnosti na primeru pravkar opisane čeljustnice: Fiziološko nujno je, da je v šestem ali vsaj sedmem mesecu ontogenetski razvoj tako napredoval, da je v denticijo že vključen prvi par stalnih molarjev. To velja za današnje rjave medvede in prav nič drugače ni moglo biti pri jamskih medvedih. Kot 36_v Irena Debeljak smo že omenili: pri začetnem prehodu na rastlinsko hrano največjo vlogo odigrajo prav prvi stalni molarji Ml, kasneje pa so se jim pridružijo tudi nekateri drugi stalni zobje (si. 1). Takrat materino mleko za rast postopoma ne zadostuje več in mladiči se morajo začeti prehranjevati tudi s trdno hrano. Mlečni zobje z izjemo zadnjih kočnikov d4 so tako majhni, da pri žvečenju trde rastlinske hrane nimajo praktično nobenega funkcionalnega pomena (Dittrich, 1960, 14-15, 50, 81-82). Starost opisane čeljustnice jamskega medveda torej ne more bistveno odstopati od naše ocene. Če bi bila starost precej višja, М^ s svojo žvekalno površino ne bi bil do- volj zgodaj "na mestu", da bi se rastoči mladič lahko primerno hranil in tako kar naj- bolje izkoristil poletno in jesensko vegetacijsko obdobje oz. hrano, ki je bila takrat na voljo. Proti nižji starosti pa pričata velikost mandibule in obraba М^, ki ni mogla na- stati ob zgolj mlečni prehrani. To bi morda lahko dokazali tudi z izotopskimi anali- zami zobnih tkiv. Menim torej, da pri ocenah starosti niso nastale velike ali celo bistvene napake in da je pri ontogenetskem razvoju zobovja jamskega medveda primerjava z rjavim medvedom umestna. 5. (Tab. 5, si. 1, 2) - Mandíbula samca, starega okoli 6,5-7,5 mesecev: Velikost te čeljustnice je že skoraj tolikšna kot pri poldrugo leto starem rjavem medvedu (tab. 16, si. 1, 2; tab. 18, si. 1). Mg s sprednjim delom prodira iz mandibule. Sklenina pri tem postopoma postaja vse svetlejša. Pri podočniku se je ravnokar pričela oblikovati stena korenine. Krona Mg je zaprta v dvigajoči se spodnječeljustnični veji in je zato značilno temno rjave barve, brez sijaja. Tanka koščena stena nad Mg je polomljena, zato se lepo vidi, da je žvekalna površina obrnjena lingvalno (proti jeziku) in s spred- njim delom usmerjena navpično navzdol. Šele z nadaljnjo rastjo čeljustnice bi nastal prostor za zadnja dva molarja. (Mg se mora pri medvedih zavrteti za 90° v dveh smereh, da se vključi v zobno vrsto.) 6. (Tab. 6, si. 1-4) - Mandíbula samice, stare okoli 6,5-7,5 mesecev: Ta čeljustnica je pripadala mladiču podobne starosti kot v prejšnjem primeru, morda je le za malen- kost starejša. М^ je bil že nekaj časa "na mestu" in v rabi, zato njegova krona nosi približno 3 milimetre velike plitve obrabne fasete. Stena korenine je skoraj v celoti oblikovana, vendar na konceh še vedno odprta (tab. 6, si. 4). Več kot pol krone Mg že gleda iz mandibule; oblikovala se je približno polovica korenine. Njena stena je zelo tanka, notranjost pa votla (tab. 6, si. 4). Korenina М^ je bolj razvita in trdna; stena je debela približno 1 milimeter. V isti etapi ontogenetskega razvoja oziroma pri isti sta- rosti zadnji spodnji molar Mg sploh še nima korenine, tanka ploska krona tega zoba pa se zlahka razlomi (tab. 5). Zelo očitno je, da so bili posamezni zobje istega mladiča različno razviti, različno mehansko odporni, in zato niso imeli enakih možnosti, da se fosilno ohranijo. Pri analizah izoliranih zob moramo računati z različnimi tafonomskimi izgubami. Do teh razlik je prišlo tako zaradi specifične oblike in velikosti posameznih zob kot tudi zaradi različne razvitosti oziroma trdnosti pri določeni starosti. Zanimivo je primerjati velikosti mandibul na tablah 4-6 (in tudi 11-15). Normalno je, da je velikost kosti odvisna od starosti osebka. Opazimo pa, da je velikost čeljust- nic tudi pri podobni starosti lahko precej različna, sorazmerno z velikostjo stalnih zob. Ti praktično v celoti zapolnjujejo čeljustnico, kar se lepo vidi na rentgenskih posnetkih. Večji zobje zahtevajo tudi več prostora. Ugotovimo lahko: 1. Jamski medved je imel izrazito večje zobe kakor današnji rjavi medved. Razu- mljivo je, da so morale biti njegove čeljusti pri isti ontogenetski stopnji in starosti precej večje in bolj robustne. Čeprav so bili mladiči jamskega medveda ob rojstvu Ontogenetski razvoj zobovja pri jamskem medvedu _^ komajda kaj večji kakor pri rjavem medvedu, je bila rast njihovih čeljusti v nasled- njih mesecih bistveno hitrejša. Tako smo na primer ugotovili, da mandíbula dobre pol leta starega jamskega medveda (tab. 5) lahko meri toliko kot pri poldrugo leto starem rjavem medvedu. Ali je bilo toliko večje tudi preostalo telo? S tako hitrim narašča- njem telesne mase pri mladičih jamskega medveda skorajda ne moremo računati. Samica bi težko vzredila dva ali celo tri tako velike mladiče že v prvem polletju, ko je bila prehrana pretežno mlečna. Bolj verjetno je, da so imeli mladiči izrazito velike če- ljusti oz. gobec. Razmerje čeljusti/telo bi torej moralo biti bistveno večje kot pri odra- slih jamskih medvedih in večje kot pri mladičih rjavega medveda. Pri edinem natan- čno opisanem in izmerjenem skeletu približno sedemmesečnega mladiča jamskega medveda (tovrstne najdbe so namreč izjemno redke!) najdemo potrditev te domneve. Avtor tega članka Ehrenberg (1964, 243-244) je bil presenečen nad odkritjem, da je obrazni del lobanje izrazito večji, kakor bi bilo pričakovati glede na možganski del lobanje, kratek trup in šibek toraks. Rekonstrukcija je pokazala, da je pri skupni dolžini 60cm in višini 30cm več kot eno tretjino zavzemala glava (Ehrenberg, 1964, 223). Menim, da takšnemu "nesorazmerju" botruje prav funkcionalni razvoj zobovja, ki je moral biti tako hiter kot pri današnjem rjavem medvedu. Čeljust pa se je pri tem ustrezno prilagodila rastočim zobem. 2. Samci jamskega medveda imajo v povprečju večje zobe kakor samice. Predvsem velja to za kanine, po katerih lahko glede na velikost določamo spol (K o by, 1949; Kurtén, 1955). Široka baza krone kanina in njegova rastoča korenina zasedata pri mladičih zelo velik del čeljustnic. Na rentgenskih posnetkih se lepo vidi, da sta višina in debelina telesa mandibule pri določeni starosti odvisni prav od velikosti kanina. Številni primerki iz Divjih bab kažejo, da so bile na isti razvojni (ontogenetski) stop- nji mandibule samic manjše in bolj gracilne kakor pri samcih. Po tem bi lahko sklepali, da je bil spolni dimorfizem na čeljustnicah jamskega medveda izražen že v prvem letu življenja. Pomisliti pa moramo še na eno možnost: da je razvoj stalnega zobovja pri samcih zaostajal v primerjavi s samicami. Vendar, če so takšne razlike v razvoju sploh obstajale, niso mogle biti bistvene zaradi že večkrat omenjenega razlo- ga: Mladiču so pri določeni starosti morali izrasti prvi stalni zobje, da se je lahko ustrezno prehranjeval. Tudi pri danes živečih medvedih v procesu izraščanja zob niso ugotovili pomembnih razlik med spoloma (Dittrich, 1960; Marks & Erickson, 1966, 393). Vsaj na enem primerku si oglejmo še stanje v zgornji čeljusti: 7. (Tab. 7, si. 1-3) - Medčel j ustnica in maksila samca, starega okoli 6,5-7,5 mese- cev: Obe kosti pri tej starosti nista neločljivo spojem. Pri današnjih medvedih se dokončno zrasteta šele pri odraslih živalih, po 4. letu (Marks & Erickson, 1966, 398-400). Na kroni М^ najdemo prve znake obrabe. Po obliki alveole sodeč, je bil P"^ ravno v fazi izraščanja; večina njegove krone je zagotovo že prodrla iz čeljustnice. Od sekalcev se je ohranil le I^, ki je malo pred poginom tega mladiča z vršičkom krone morda že prodrl skozi diesen. Ležišče korenine je nepoškodovano, tako da lahko ugotovimo, da je bil zob že dokončno izraščen. Nasprotno pa ozka odprtina alveole dokazuje, da se izraščanje tega inciziva sploh še ni začelo. Nad pravkar omenjeno alveolo je ohranjena tudi plitva alveola mlečnega di^, ki je pri tej starosti že tičal v če- ljusti, čez kak mesec pa bi po naravni poti izpadel iz dlesni. Zgornji podočnik je skrit v maksili. Na rentgenskem posnetku (tab. 7, si. 3) vidimo, da se njegova korenina še ni začela formirati. Krona je votla in še precej pod, ali bolje rečeno nad robom zgornje čeljustnice. Globoko ležišče korenine mlečnega podočnika je v celoti ohranjeno in s trdno koščeno steno popolnoma ločeno od razvijajoče krone stalnega kanina, zato 38_v_Irena Debeljak sklepamo, da korenina mlečnega kanina na tej stopnji ontogenetskega razvoja še ni bila prizadeta zaradi kontaktne resorbcije. Preden končamo z opisom ontogenetskega razvoja zobovja v sedmem in osmem mesecu življenja, naj omenim še eno zanimivost: Med juvenilnimi čeljustnicami iz Divjih bab I imamo največ primerkov ravno iz pravkar obravnavanega starostnega obdobja, čeprav bi po ugotovitvah drugih raziskovalcev (Ehrenberg, 1931, 1964; Kurtén, 1958, 1976) ostanki 7-mesečnih mladičev, ki so poginili sredi poletja, morali biti prava redkost. Splošno uveljavljeno prepričanje, ki je obveljalo v zadnjih deset- letjih, je, da množični ostanki jamskega medveda v jamah izvirajo od živali, ki so po- ginile zaradi izčrpanosti med dolgo hibernacijo, pozimi in predvsem tik pred nasto- pom pomladi. Vendar, tudi analiza izoliranih zob d4 in М^ je pokazala, da izredno ve- lik delež v fosilni populaciji zavzemajo prav mladiči, ki so poginili pri domnevni sta- rosti 6-8 mesecev, od julija do septembra (Debeljak, 1996a, 1997). Divje babe I kot tipično najdišče jamskega medveda gotovo ne predstavljajo nobene izjeme, zato so takšni rezultati o sestavi fosilne populacije presenetljivi in nepričakovani. Razložimo jih lahko na dva različna načina: a) Naše ocene individualne starosti (in s tem tudi izoliranih juvenilnih zob) niso pravilne, in tako najpogostejša starostna skupina domnevno 7-mesečnih živali dejan- sko predstavlja tiste mladiče, ki so poginili med drugo hibernacijo. V tem primeru bi moral ontogenetski razvoj zobovja jamskega medveda kar za 6 mesecev zaostajati za ontogenetskim razvojem, ki so ga ugotovili pri današnjih medvedih. Glede na že ome- njene prehranjevalne navade in potrebe v prvem letu se to zdi skoraj nemogoče. Po drugi strani pa bi lahko v podporo zgornji domnevi navedli videz prve tanke cemen- tne obloge na korenini М^. To cementno plast sicer razlagamo kot "neonatno linijo" (Debeljak, 1996a, 29-30, tab. 26-28), vendar je precej podobna "zimskim" prira- stnicam. b) Druga možna interpretacija očitnega razhajanja med pričakovanim in ugotov- ljenim mortalitetnim profilom: Ocene starosti so pravilne. Življenjske navade in smrt- nost famskega medveda so potemtakem bistveno drugačne, kot smo domnevali do zdaj. (Podobno je že Musil (1965, 74-76) na podlagi merjenja dolgih kosti okončin prišel do sklepa, da so jamski medvedi zahajali v jamo Pod hradem in tam umirali tudi v poletnih mesecih.) Dokončen odgovor na zastavljena vprašanja bodo morda omogočile nadaljnje raziskave ontogenetskega razvoja pri današnjih, v različnih okoljih živečih medvedih, pa tudi natančne analize zobnega cementa pri mladičih. Od devetega meseca do dopolnjenega prvega leta V 9. ali 10. mesecu življenja pri medvedih dokončno izrastejo drugi spodnji molar- ji Mg. Zadnji zgornji molarji М^ začnejo izraščati v devetem mesecu. Po desetem me- secu že lahko začnejo prodirati skozi čeljustnico stalni kanini. Malo pred dopolnjenim prvim letom (11. ali 12. mesec) pa predrejo diesen tudi zadnji spodnji molarji Mg. Za- radi poševne lege in izrazito ploske krone mine še precej časa, preden v celoti izraste- jo. Ehrenberg (1931, tab. 120, si. 6) je objavil fotografijo mandibule mladiča jam- skega medveda, ki bi mu lahko pripisali starost približno 8-9 mesecev. Na tabli 8, si. 1 in tabli 10, si. 1 je spodnja čeljustnica recentnega, okoli 10 mesecev starega rjavega medveda iz Slovenije. Sprednji del Mg je "zunaj". Vršički stalnih ka- Ontogenetski razvoj zobovja pri jamskem medvedu _^ ninov so ravnokar pogledali iz alveole, vendar skozi diesen še niso prodrli. Latero- distalno od njih so mlečni kanini. Vsi drugi mlečni zobje so do te starosti že izpadli. Mandíbula na tabli 9, si. 1 in tabli 10, si. 2 je pripadala okoli eno leto staremu ko- čevskemu rjavemu medvedu. Nekaj več kot 1 cm kanina sega čez rob alveole. Ob njem še vedno tiči mlečni kanin z obrabljeno krono in močno resorbirano korenino. V času zamenjave podočnikov imajo medvedje kar nekaj časa v dlesnih stalne in mlečne kanine hkrati. Mlečni kanini izpadejo šele pri starosti 12-15 mesecev, med zimova- njem v brlogu. Zgornja primera mandibul rjavega medveda predstavljamo zato, ker za obravna- vano starostno obdobje v zbirki iz Divjih bab nimamo nobene primerne čeljustnice. Tudi pri izoliranih zobeh smo opazili zelo izrazito vrzel, ki kaže, da v Divjih babah skorajda ni ostankov jamskih medvedov, ki bi poginili med 10. mesecem in dopolnje- nim prvim letom življenja, to je v prvi polovici zimovanja v brlogu (Debeljak, 1996 a, 1997). Vendar, glede na zgornjo razpravo je možno tudi to, da manjkajoča starostna sku- pina predstavlja mladiče iz naslednjega poletja. Od enega leta do poldrugega leta V času od enega leta do poldrugega leta se pri medvedih končuje proces izraščanja stalnega zobovja. Individualne razlike pri tem postajajo vse bolj izrazite (Dittrich, 1960), zato starosti ne moremo določiti tako natančno kot prej. Zadnji stalni zobje (М^, Mg in kanini) so pri poldrugo leto starih recentnih medvedih praviloma dokon- čno izraščeni. To obdobje ontogenetskega razvoja pri jamskem medvedu nam pred- stavljajo naslednji trije primerki. Njihovo individualno starost sem ocenila na podlagi podatkov za današnje rjave medvede. Morali pa bi upoštevati tudi možnost, da je bil ontogenetski razvoj zobovja pri jamskem medvedu počasnejši. V tem primeru bi lahko naslednje tri mandibule pripadale dveletnim ali celo nekoliko starejšim mladičem, ki so poginili v svoji tretji zimi. 8. (Tab. 11, si. 1, 2; tab. 13, si. 1) - Mandíbula samca, starega 12-15 mesecev: Veli- kost te mandibule je bila tolikšna kot pri odraslem recentnem rjavem medvedu. Sim- fizni del, kjer sta bili leva in desna mandíbula povezani, je najbrž patološko spreme- njen. Vnetna sprememba je morda nastala ob kakšni travmatski poškodbi čeljusti. Kanin je že precej razvit. Dober centimeter in pol krone gleda iz alveole in oblikovana je že več kot polovica stene korenine. Sprednja polovica žvekalne površine Mg je rahlo obrabljena. Velik del krone Mg še ni prodrl skozi diesen. Njegova lega je glede na pre- ostale zobe še vedno poševna. Pri izraščanju zadnjega kočnika Mg se je včasih zgodilo, da se je njegova krona za- gozdila ob krono sosednega Mg. Na nekaterih mandibulah jamskega medveda lahko opazimo s tem povezane patološke spremembe, ki so živalim prav gotovo povzročale hude težave. Po nekaterih avtorjih so bile nepravilnosti pri izraščanju zadnji kočni- kov glavni ali pa vsaj zelo velik vzrok smrtnosti pri mladičih v drugi zimi (Ehren- berg, 1931; Abel, 1931.) Z raziskavami v Divjih babah tega nismo mogli potrditi. Menim, da bi omenjene težave jamske medvede resno ogrožale kvečjemu kasneje v življenju. Čeprav je seveda mogoče, da se je morebitna okužba pri oslabelem enolet- nem mladiču lahko končala tudi s smrtnim izidom. 9. (Tab. 12, si. 1, 2; tab. 13, si. 2) - Mandíbula samice, stare okoli 15 mesecev: Oblikovani sta že dve tretjini korenine podočnika. Krona še ni v celoti izrastla; za 40_v Irena Debeljak dobra dva centimetra sega čez rob alveole. Mg še ni čisto "na mestu"oz. v okluzalni ravnini. Korenina Р^ in Mg je na konceh še vedno odprta. М^ ima zaprto korenino in "oglajeno" krono s posameznimi, 2-3 mm širokimi obrabnimi fasetami. Tudi na sprednjem delu Mg je obraba že očitna. Na žvekalni površini Mg še ni sledov obrabe. Zaradi gneče v zobni vrsti posamezni zobje pritiskajo eden na drugega. (Po prvem letu so se ob stiku nekaterih zob začele nakazovati značilne fasete ter se sčasoma še povečale in poglobile. Še posebej je to izrazito na anteriorni steni krone Mg in posteri- orni steni krone М^. Takšen tip obrabe imenujemo aproksimalna obraba; za razliko od okluzalne obrabe na žvekalni površini.) Za primerjavo lahko vzamemo spodnjo čeljustnico slabo leto in pol starega rjave- ga medveda iz okolice Kočevja (tab. 16, si. 1, 2.; tab. 18, si. 1): Tudi pri njem kanini še niso docela izrastli. Korenine zob pa so z izjemo Mg in kanina že zaprte. Krona Mg še ni v celoti pogledala iz dlesni. Na podobni ontogenetski stopnji je naslednji primerek: 10. (Tab. 14, si. 1, 2; tab. 15, si. 1-3) - Mandíbula samice jamskega medveda, stare okoli eno leto in pol: Kanin je nekoliko bolj razvit kakor pri ravnokar omenjenem rjavem medvedu. Krona je praktično v celoti izrastla, manjka samo še kakšen centime- ter korenine. Mg je že na svojem mestu v zobni vrsti. М^ je še nekoliko bolj obrabljen kakor pri prejšnjih primerkih. Površina je zglajena in posuta z majhnimi obrabnimi fasetami. Ob stiku М^ in Mg je na obeh zobeh nastala izrazita faseta (aproksimalna obraba). Na posteriorni steni krone М^ je ta faseta široka kar 4 mm. Korenina М^ se je zaprla že v prvem letu. Pri starosti okoli poldrugega leta je njena stena debela pri- bližno 2,5-2,75 milimetra. Pri Mg sta konici korenine le še nekoliko perforirani. Korenina Mg pa še vedno široko zeva in ima zelo krhko steno (tab. 15, si. 3). Izolirane zobe ponavadi opredelijo kot juvenilne, če je korenina odprta, oziroma adultne, ko je korenina zaprta. Pri tem so nekateri zobje istega osebka označeni kot adultni, drugi, ki v razvoju zaostajajo, pa kot juvenilni. Problem pa ni samo v dvolič- nosti podatkov. Omenjena klasifikacija ni ustrezna predvsem zato, ker se na ta način velik delež zob mladičev napačno prišteje med odrasle (na to je bilo opozorjeno tudi v: Turk et al., 1992). Medved odraste šele okoli 4. leta. Korenina М^ se zapre že pred dopolnjenim prvim letom starosti, Mg in P^ pa pri poldrugem letu. Zaprtost korenine je lahko kvečjemu kriterij za ugotavljanje odraslosti po zadnjih molarjih in kaninih. Kot soavtorica sem dolžna opozoriti na napako v članku izpred petih let (Turk et al., 1992), ko ontogenetskega razvoja zobovja pri medvedu še nismo dovolj dobro poznali. V omenjenemu prispevku so bile statistično obdelane mere "adultnih" molarjev М^, z namenom, da bi preučili razmerje obeh spolov med odraslimi jamski- mi medvedi. V resnici gre za zobe, ki bi jih morali pripisati starejšim mladičem (dveletniki, triletniki, morda še štiriletniki). Njihova korenina je bila zaprta, in na podlagi tega kriterija smo jih napačno prišteli med odrasle. Nadaljnji razvoj zob in čeljusti Domnevno na polovici ali proti koncu drugega leta življenja so imeli jamski me- dvedi že izraščeno cfelotno stalno zobovje. Zobje pa so se kljub temu razvijali še na- prej. Prvotno votle korenine in krone so se vse bolj zapolnjevale z zobovino ali dentin- om. Končno je v sredini ostal samo še ozek kanal in pulpna votlina na prehodu iz korenine v krono. Predvidevamo, da so se pri jamskem medvedu okoli 4. leta zaprle še zadnje zobne korenine: М^, Mg in kaninov. V začetku eksplozivna rast čeljusti se je v naslednjih letih vse bolj umirjala. Ontogenetski razvoj zobovja pri jamskem medvedu _^ 11. (Tab. 17, si. 1, 2; tab. 18, si. 2) - Mandíbula subadultnega samca, starega okoli 4 leta: Starost tega primerka je bila določena s štetjem prirastnic na zobnem cementu. Ta metoda velja za najbolj objektivno in se vsesplošno uporablja za ocenjevanje indi- vidualne starosti pri divjih živalih (več v: Debeljak, 1996a, b). Zgoraj omenjeni proces odlaganja dentina v notranjosti zob je že precej napredoval, kar se lepo vidi na rentgenskem posnetku (tab. 18, si. 2). Krona М^ je najbolj obrabljena (predvsem pro- tokonid in hipokonid). Mg manj in Mg zelo malo (tab. 17, si. 2). Ob stiku posameznih molarjev so nastale precej globoke fasete. Na posteriorni steni krone М^ je takšna faseta široka že več kot 6 mm. Dolžine krone tako ne bi bilo več mogoče res natančno izmeriti. Po rentgenski sliki sodeč, se korenini kanina in Mg še nista docela zaprli, vendar ne manjka dosti. Pri recentnih medvedih se korenina kanina zapre okoli 4. leta (Marks & Erickson, 1966, 395, 397), to je v času, ko dosežejo spolno zrelost. Pravkar opisana mandíbula še ni dosegla svoje končne velikosti. Mandibule dora- slih samcev merijo v dolžino 5-10 centimetrov več. Rast čeljusti je torej napredovala tudi po četrtem letu. Pri recentnem črnem medvedu glava samcev raste prvih 8 let, pri samicah pa se ta rast ustavi nekoliko prej, kmalu po spolni zrelosti (Marks & Erickson, 1966, 400-402). Najbrž je bilo podobno tudi pri jamskih medvedih. Sklep V prispevku je bil predstavljen ontogenetski razvoj zobovja pri jamskem medvedu oziroma pri medvedih nasploh. Proces zamenjave mlečnega zobovja in izraščanja stalnih zob se večinoma konča do poldrugega leta življenja. Do takrat so posamezne ontogenetske faze dober indikator individualne starosti. S pomočjo opisanih primerov in zbranih podatkov bomo lahko ocenili starost ju- venilnih čeljustnic jamskega medveda in za silo tudi izoliranih juvenilnih zob. V bo- doče bo treba natančno predstaviti tudi ontogenetski razvoj in kriterije za določanje individualne starosti pri posameznih (izoliranih) zobeh, ki so najpogosteje ohranjeni in najbolj informativni fosilni ostanki jamskega medveda. V sklepu naj še enkrat povzamem glavne ugotovitve: - Proces rasti zob in zamenjave mlečnega zobovja s stalnim je pri jamskem medve- du potekal na enak način, prek enakih in verjetno tudi sinhronih razvojnih faz kot pri sorodnih, danes živečih medvedih. - Sklepamo lahko, da določena ontogenetska stopnja razvitosti zobovja jamskega medveda ustreza približno isti starosti osebka kot pri rjavem medvedu. Razvoj zobov- ja pri jamskem medvedu ni smel bistveno zaostajati, saj so mladiči pri določeni starosti (6. ali vsaj 7. mesec življenja) potrebovali prvi par stalnih molarjev (М^&М^), da so lahko pričeli žvečiti trdno rastlinsko hrano. - Ta argument govori proti drugi možnosti, da je bil ontogenetski razvoj zobovja pri jamskem medvedu dejansko precej počasnejši kot pri današnjih medvedih. Takšna posebnost bi (v določenih okoliščinah) lahko ogrozila obstoj vrste. Omenjene domne- ve pa zaenkrat vendarle ne moremo in ne smemo povsem ovreči. - Velikost čeljustnic je bila v prvem letu življenja (pa tudi kasneje) odvisna od veli- kosti stalnih zob, ki so se v temu času v njej razvijali in jo skoraj v celoti zapolnjevali. - Rast čeljusti je bila pri mladičih jamskega medveda bistveno hitrejša kakor pri današnjem rjavem medvedu. Že pri enem letu je bila njihova mandíbula tako velika kot pri odraslem rjavem medvedu. To seveda ne pomeni, da je bilo toliko večje tudi preostalo telo. 42_v Irena Debeljak - Domnevamo, da je bil pri jamskih medvedih sekundarni spolni dimorfizem izra- žen že v prvem letu življenja; samci so imeli večje čeljusti od samic. - Splošno uveljavljena metoda ločevanja zob na juvenilne, z odprto korenino in adultne, če je korenina zaprta, za večino zob pri jamskem medvedu ni ustrezna. Medved odraste okoli 4. leta. Korenina М^ pa se na primer zapre že v prvem letu živl- jenja (po 8. mesecu), večina drugih stalnih zob do poldrugega leta in samo korenine М^, Mg in kaninov šele pri priblišno štirih letih. - Pri študiju juvenilnih čeljustnic iz paleolitskega najdišča Divje babe I nismo mo- gli spregledati dejstva, da je večina primerkov nekoč verjetno pripadala približno sedemmesečnim mladičem, ki so torej poginili sredi poletja. To je v nasprotju z dose- danjim mnenjem, da množični ostanki v tipičnih nahajališčih jamskega medveda iz- virajo od živali, ki so zaradi izčrpanosti poginile med hibernacijo, pred nastopom po- mladi. - Zanimiv problem in naloga v prihodnosti bo: z nadaljnjimi raziskavami in do- datnimi podatki dokazati to trditev in jo smiselno obrazložiti. Zahvala Ivanu Turku, vodji izkopavanj v Divjih babah I, se zahvaljujem za material, ki mi ga je prepustil v obdelavo. Izkopavanja izvaja Inštitut za arheologijo Znanstvenorazi- skovalnega centra SAZU. Na Kliniki za kirurgijo in male živali Veterinarske fakul- tete v Ljubljani so prijazno omogočili rentgensko slikanje čeljustnic jamskega in rjavega medveda, ki je lepo uspelo po strokovni zaslugi veterinarjev Teodore Ivanuša, Janeza Štublja in Gregorja Freliha. Andrej Bidovec (Veterinarska fakulteta, Ljublja- na) in Ciril Štrumbelj (Gojitveno lovišče Medved, Kočevje) sta posredovala za primer- javo potrebne lobanje mladičev recentnega rjavega medveda iz Slovenije. Vida Pohar je pregledala manuskript. Iskreno se zahvaljujem tudi vsem drugim, ki so kakorkoli pomagali pri nastanku tega prispevka. References Abel, O., 1931: Die Degeneration des Höhlenbären von Mixnitz und deren wahrscheinliche Ursachen. In: O. Abel & G. Kyrie (eds.), Die Drachenhöhle bei Mixnitz. - Speläolog. Monogr. 7-9, 719-744, Wien. Bocherens, H., Fi z et, M. & M arlotti. A., 1994: Diet, physiology and ecology of fossil mammals as inferred from stable carbon and nitrogen isotope biogeochemistry: implications for Pleistocene bears. - Paleogeogr. Paleoclim. Palaeoecol. 107, 213-225, Amsterdam. Couturier, M. A. J., 1954: L'ours brun {Ursus arctos L.). - 904 pp., Grenoble. Debeljak, L, 1996a: Starostna sestava populacije jamskega medveda iz Divjih bab. (Age structure of cave bear population from the Divje babe Cave.) - Magistrska naloga. Manuscript, 70 pp., 36 tab. Naravoslovnotehniška fakulteta. Oddelek za geologijo, Ljubljana. D e b e 1 j a k. L, 1996b: A simple preparation technique of cave bear teeth for age determina- tion by cementum increments. - Rev. Paléobiol. 15/1, 105-108, Genève. Debeljak, L, 1997: Age composition of the cave bear population from the Divje babe I Cave. - Int. Meeting on Man and Bear, Auberives-Pont en Royans (Vercors - Isère). (In press.) D i 11 r i c h, L., 1960: Milchgebißentwicklung und Zahnwechsel beim Braunbären {Ursus arc- tos L.) und anderen Ursiden. - Morph. Jb. 101/1, 1-141, Leipzig. Ontogenetic development of dentition in the cave bear__43 Ehrenberg, K., 1931: Über die ontogenetische Entwicklung des Höhlenbären. In: O. Abel & G. Kyrie (eds.). Die Drachenhöhle bei Mixnitz. - Speläolog. Monogr. 7-9, 624-710, Wien. Ehrenberg, K., 1964: Ein Jungbärenskelett und andere Höhlenbärenreste aus der Bären- höhle im Hartlesgraben bei Hieflau (Steiermark). - Ann. Naturhistor. Mus. Wien 67, 189-252, Wien. Ehrenberg, K., 1973: Ein fast vollständiges Höhlenbärenneonatenskelett aus der Salz- ofenhöhle im Toten Gebirge. - Ann. Naturhistor. Mus. Wien 77, 69-113, Wien. K o by, F.-Ed., 1949: Le dimorphisme sexuel des canines d'Ursus arctos et d'î7. spelaeus. - Rev Suisse Zool. 56, 675-687, Genève. Koby, E-Ed., 1952: La dentition lactéale d'Ursus spelaeus. - Rev. Suisse Zool. 59, 511-541, Genève. KryStufek, B., 1991: Sesalci Slovenije. - Prirodoslovni muzej Slovenije, 294 pp., Ljub- ljana. Kurtén, В., 1955: Sex dimorphism and size trends in the cave bear, Ursus spelaeus Rosen- müller & Heinroth. - Acta Zool. Fennica 90, 1-48, Helsinki. Kurtén, B., 1958: Life and death of the Pleistocene cave bear A study in paleoecology. - Acta Zool. Fennica 95, 1-59, Helsinki. Kurtén, B., 1976: The cave bear story. Life and death of a vanished animal. - Columbia Univ. Press, 163 pp.. New York. Macdonald, D. (ed.), 1985: The Encyclopedia of Mammals. Vol. 1. - Equinox (Oxford) Ltd., London. Macdonald, D. (ed.), 1996: Velika enciklopedija. Sesalci. - Založba Mladinska knjiga, 980 pp., Ljubljana. Marks, S. A. & Erickson, A. W, 1966: Age determination in the black bear. - J. Wildl. Manage. 30/2, 389-410, Washington. Musil, R., 1965: Die Bärenhöhle Pod hradem. Die Entwicklung der Höhlenbären im letzten Glazial. - Anthropos 18, 7-92, Brno. Nelson, D. E. & Ku, T.-L., 1997: Radiokarbonsko datiranje kosti in oglja iz Divjih bab I. Radiocarbon dating of bone and charcoal from Divje babe I cave. In: I. Turk (ed.). - Opera Instituti Archaeologici Sloveniae 2, 51-65, Založba ZRC, Ljubljana. P o h 1 e, H., 1923: Über den Zahnwechsel der Bären. - Zool. Anz. 55, 266-277, Leipzig. Rädulescu, C. & Samson, P, 1959: Contribution à la Connaissance de la Dentition lac- téale d'Ursus spelaeus. - Eiszeitalter u. Gegenwart 10, 205-216, Öhringen. Rausch, R. L., 1961: Notes on the black bear {Ursus americanus Pallas) in Alaska, with particular reference to dentition and growth. - Z. Säugetierk. 26/2, 77-107, Berlin. Rode, K., 1935: Untersuchungen über das Gebiß der Bären. - Monogr Geol. Palaeont. Ser. II, H. 7, 162 pp., Leipzig. Turk, L (ed.), 1997: Moustérienska "koščena piščal" in druge najdbe iz Divjih bab I v Sloveniji. Mousterian "bone flute" and other finds from Divje babe I cave site in Slovenia. - Opera Instituti Archaeologici Sloveniae 2, 223 pp. Založba ZRC, Ljubljana. Turk, L, Dirjec, J., Strmole, D., Kranjc, A. & Čar, J., 1989 a: Stratigrafija Divjih bab L Izsledki izkopavanj 1980-1986. (Stratigraphy of Divje babe L Results of excavations 1980-1986.) -Razpr IV. razr SAZU 30, 161-207, Ljubljana. Turk, L, Dirjec, J. & Culiberg, M., 1989b: Divje babe I - novo paleolitsko najdišče in skupinsko grobišče jamskega medveda. Poskus tafonomske analize na podlagi vzorcev iz dveh sedimentnih in arheoloških kompleksov. (Divje babe I - a new palaeolithic site and a common grave of the cave bear. An attempt at a taphonomic analysis based on samples from a pair of sedimentary and cultural units.) - Arh. vest. 39-40, 13-60, Ljubljana. Turk, I., Dir j e c, J., Deb el j ak, I. & Hub er, D., 1992: Divje babe I-poskus uporabe sta- tistične analize množičnih živalskih ostankov v paleolitski arheologiji. IV. Posamično najdeni zobje jamskega medveda. (Divje babe I - an attempt to apply statistical analysis to the mass ani- mal remains in the palaeolithic archaeology. IV. Isolated teeth of cave bear.) - Arh. vest. 43, 7-22, Ljubljana. 44 v Irena Debeljak Plate 1 - Tabla 1 Cave bear; left and right mandible of two neonates (from Quad. 86, spit XV, and Quad. 24, spit XVII). Divje babe I 1 From above. Natural size (left) and magnification two times (right) a = germ of deciduous canine, b = germ of deciduous premolar d^ 2 Buccal side of right mandible. Natural size (left) and magnification two times (right) Jamski medved; leva in desna mandíbula dveh neonatov (iz Kv. 86, izkop XV in Kv. 24, izkop XVII). Divje babe I 1 Od zgoraj. Naravna velikost (levo) in dvakrat povečano (desno) a = zametek mlečnega kanina, b = zametek mlečnega premolarja d^ 2 Bukalna stran desne mandibule. Naravna velikost (levo) in dvakrat povečano (desno) Ontogenetic development of dentition in the cave bear 45 Plate 2 - Tabla 2 Cave bear; left mandible (invt. num. 1357) of a cub approx. 2-2.5 months old. Divje babe I. Natural size 1 From above a = alveolus for d3, b = alveolus for d^, c = fissure above Mj 2 Lateral x-ray photograph (made at the Clinic for surgery and small animals of the Veteri- nary Faculty in Ljubljana) 3 Schematic illustration of germs of permanent teeth Jamski medved; leva mandíbula (inv. št. 1357) mladiča, starega okoli 2-2,5 meseca. Divje babe I. Naravna velikost 1 Od zgoraj a = alveola za dg, b = alveola za d^, c = reža nad M, 2 Rentgenski posnetek od strani (izdelan na Kliniki za kirurgijo in male živali Veterinarske fakultete v Ljubljani) 3 Shematska ponazoritev zametkov stalnih zob 46_v_Irena Debeljak Plate 3 Cave bear; left and right mandible (invt. num. 1375 and 1380) of a cub 2.5—3 months old. Divje babe I. Natural size 1 From above a = alveolae for di^_3, b = alveolus for dc, c = alveolus for dg, d = alveolus for d^, e = М^ 2 Lateral x-ray photograph (made at the Clinic for surgery and small animals of the Veteri- nary Faculty in Ljubljana) 3 Schematic illustration of germs of permanent teeth Tabla 3 Jamski medved; leva in desna mandíbula (inv. št. 1375 in 1380) mladiča, starega okoli 2,5-3 mesece. Divje babe I. Naravna velikost 1 Od zgoraj a = alveole za dij_o, b = alveola za dc, c = alveola za dg, d = alveola za d^, e = М^ 2 Rentgenski posnetek leve mandibule od strani (izdelan na Kliniki za kirurgijo in male živali Veterinarske fakultete v Ljubljani) 3 Shematska ponazoritev zametkov stalnih zob Ontogenetic development of dentition in the cave bear 47 48_v Irena Debeljak Plate 4 Cave bear, right mandible (invt. num. 1033) of a female approx. 6-7 months old. Divje babe I. Natural size 1 Lingual side 2 From above a = alveolus of dc-C, b = alveolus of d,, c = alveolus of dg 3 Lateral x-ray photograph (made at the Clinic for surgery and small animals of the Veteri- nary Faculty in Ljubljana) 4 Isolated molar М^; lingual side 5 Isolated molar М^; from below Tabla 4 Jamski medved; desna mandíbula (inv. št. 1033) samice, stare okoli 6-7 mesecev. Divje babe I. Naravna velikost 1 Lingvalna stran 2 Od zgoraj a = alveola dc-C, b = alveola d^, c = alveola d, 3 Rentgenski posnetek od strani (izdelan na Kliniki za kirurgijo in male živali Veterinarske fakultete v Ljubljani) 4 Izoliran molar М^; lingvalna stran 5 Izoliran molar М^; od spodaj Ontogenetic development of dentition in the cave bear 49 50_v Irena Debeljak Plate 5 Cave bear; left mandible of a male approx. 6.5-7.5 months old. Divje babe I. Natural size 1 Lingual side 2 Lateral x-ray photograph (made at the Clinic for surgery and small animals of the Veteri- nary Faculty in Ljubljana) Tabla 5 Jamski medved; leva mandíbula samca, starega okoli 6,5-7,5 mesecev. Divje babe I. Naravna velikost 1 Lingvalna stran 2 Rentgenski posnetek od strani (izdelan na Kliniki za kirurgijo in male živali Veterinarske fakultete v Ljubljani) Ontogenetic development of dentition in the cave bear 51 52_v Irena Debeljak Plate 6 Cave bear; right mandible (invt. num. 1095) of a female approx. 6.5-7.5 months old. Divje babe I. Natural size 1 Lingual side 2 Lateral x-ray photograph. Mj^ is isolated; lower part of its root is sawn off. (x-ray was made at the Clinic for surgery and small animals of the Veterinary Faculty in Ljubljana) 3 Isolated molars М^ and Mg; lingual side 4 Isolated molars Mj^ and Mg; from below Tabla 6 Jamski medved; desna mandíbula (inv. št. 1095) samice, stare okoli 6,5-7,5 mesecev. Divje babe I. Naravna velikost 1 Lingvalna stran 2 Rentgenski posnetek od strani. Mj^ je izoliran; spodnji del korenine je odžagan. (Posnetek je bil izdelan na Kliniki za kirurgijo m male živali Veterinarske fakultete v Ljubljani) 3 Izolirana molarja М^ in Mg; lingvalna stran 4 Izolirana molarja Mj^ in Mg; od spodaj n„,„„„etic develoomentoftotU^^ 53 54_v Irena Debeljak Plate 7 Cave bear; left premaxilla and maxilla of a male approx. 6.5-7.5 months old. Divje babe I. Natural size 1 Buccal side 2 Occlusal 3 Lateral x-ray photograph (made at the Clinic for surgery and small animals of the Veteri- nary Faculty in Ljubljana) Tabla 7 Jamski medved; leva medčeljustnica in zgornja čeljustnica samca, starega okoli 6,5-7,5 mesecev. Divje babe I. Naravna velikost 1 Bukalna stran 2 Okluzalno 3 Rentgenski posnetek od strani (izdelan na Kliniki za kirurgijo in male živali Veterinarske fakultete v Ljubljani) Ontogenetic development of dentition in the cave bear 55 56_v Irena Debeljak Plate 8 Present-day brown bear; mandible (upper view) of a male approx. 10 months old. Natural size (Cub found on 28 Nov. 1989, about two weeks' decay.) LD Draga Trava - Loški potok. Collec- tion of the Veterinary Faculty in Ljubljana (No. 178/89) See also PL 10, fig. 1 (buccal side of the same specimen) Tabla 8 Današnji rjavi medved; mandíbula (slikana od zgoraj) samca, starega okoli 10 mesecev. Naravna velikost (Mladič najden 28. 11. 89, razpadal približno 2 tedna.) LD Draga Trava - Loški potok. Zbirka Veterinarske fakultete v Ljubljani (št. 178/89) Glej še tab. 10, si. 1 (bukalna stran istega primerka) Ontogenetic development of dentition in the cave bear 57 58_v Irena Debeljak Plate 9 Recent brown bear; mandible (upper view) of a female approx. one year old. Natural size (Cub killed on 26 Dec. 1986, weight 55 kg). Collection of the "Medved" breeding and hunting ground, Kočevje See also PI. 10, fig. 2 (buccal side of the same specimen) Tabla 9 Današnji rjavi medved; mandíbula (slikana od zgoraj) samice, stare okoli eno leto. Naravna velikost (Uplenjena 26. 12. 86, teža 55 kg.) Zbirka Gojitvenega lovišča "Medved", Kočevje Glej še tab. 10, si. 2 (bukalna stran istega primerka) Ontogenetic development of dentition in the cave bear 59 60_v Irena Debeljak Plate 10 1 Recent brown bear; buccal side of right mandible of a male approx. 10 months old. Natural size See also PI. 8 (upper view of the same specimen) 2 Recent brown bear; buccal side of left mandible of a female approx. one year old. Natural size See also PI. 9 (upper view of the same specimen) Tabla 10 1 Današnji rjavi medved; bukalna stran desne mandibule samca, starega okoli 10 mesecev. Naravna velikost Glej še tab. 8 (isti primerek od zgoraj) 2 Recentni rjavi medved; bukalna stran leve mandibule samice, stare okoli eno leto. Naravna velikost Glej še tab. 9 (isti primerek od zgoraj) Ontogenetic development of dentition in the cave bear 61 62_v Irena Debeljak Plate 11 Cave bear; left mandible (invt. num. 1053) of a male approx. 12-15 months old. Divje babe I. Natural size 1 Lingual side 2 From above See also PL 13, fig. 1 (lateral x-ray photograph of the same specimen) Tabla 11 Jamski medved; leva mandíbula (inv. št. 1053) samca, starega okoli 12-15 mesecev. Divje babe I. Naravna velikost 1 Lingvalna stran 2 Od zgoraj Glej še tab. 13, si. 1 (lateralni rentgenski posnetek istega primerka) Ontogenetic development of dentition in the cave bear 63 64_v Irena Debeljak Plate 12 Cave bear; left mandible (invt. num. 1385) of a female approx. 15 months old. Divje babe I. Natural size 1 Lingual side 2 From above See also PI. 13, fig. 2 (lateral x-ray photograph of the same specimen) Tabla 12 Jamski medved; leva mandibula (inv. št. 1385) samice, stare okoli 15 mesecev. Divje babe I. Naravna velikost 1 Lingvalna stran 2 Od zgoraj Glej še tab. 13, si. 2 (stranski rentgenski posnetek istega primerka) Ontogenetic development of dentition in the cave bear 65 66_v Irena Debeljak Plate 13 Cave bear; left mandible (invt. num. 1053) of a male approx. 12-15 months old; lateral x-ray photograph (made at the Clinic for surgery and small animals of the Veterinary Faculty in Ljubljana) See also PI. 11, figs. 1, 2 (lingual side and upper view of the same specimen) Cave bear; left mandible (invt. num. 1385) of a female approx. 15 months old; lateral x-ray photograph (made at the Clinic for surgery and small animals of the Veterinary Faculty in Ljubljana) See also PI. 12, figs. 1, 2 (lingual side and upper view of the same specimen) Tabla 13 Jamski medved; leva mandibula (inv. št. 1053) samca, starega okoli 12-15 mesecev; stranski rentgenski posnetek (izdelan na Kliniki za kirurgijo in male živali Veterinarske fakultete v Ljubljani) Glej še tab. 11, si. 1, 2 (lingvalna in zgornja stran istega primerka) Jamski medved; leva mandibula (inv. št. 1385) samice, stare okoli 15 mesecev; stranski rent- genski posnetek (izdelan na Kliniki za kirurgijo in male živali Veterinarske fakultete v Ljubljani) Glej še tab. 12, si. 1, 2 (lingvalna in zgornja stran istega primerka) Ontogenetic development of dentition in the cave bear 67 68_v Irena Debeljak Plate 14 Cave bear; left mandible (invt. num. 1428) of a female about one and a half years old. Divje babe I. Natural size 1 Lingual side 2 From above See also PI. 15, figs. 1-3 (lateral x-ray photograph and isolated molars of the same specimen) Tabla 14 Jamski medved; leva mandibula (inv. št. 1428) samice, stare okoli eno leto in pol. Divje babe L Naravna velikost 1 Lingvalna stran 2 Od zgoraj Glej še tab. 15, si. 1-3 (stranski rentgenski posnetek in izolirani molarji istega primerka) Ontogenetic development of dentition in the cave bear 69 70_v Irena Debeljak Plate 15 Cave bear; left mandible (invt. num. 1428) of a female about one and a half years old. Divje babe I. Natural size 1 Lateral x-ray photograph. Mj is isolated; lower part of its root is sawn off. (x-ray was made at the Clinic for surgery and small animals of the Veterinary Faculty in Ljubljana) 2 Isolated molars М^, Mg and Mg; buccal side 3 Isolated molars М^, Mg and Mg; from below See also PL 14, figs. 1, 2 (lingual side and upper view of the same specimen) Tabla 15 Jamski medved; leva mandibula (inv. št. 1428) samice, stare okoli eno leto in pol. Divje babe L Naravna velikost 1 Rentgenski posnetek od strani. Mj^ je izoliran; spodnji del korenine je odžagan. (Posnetek je bil izdelan na Kliniki za kirurgijo m male živali Veterinarske fakultete v Ljubljani.) 2 Izolirani molarji М^, Mg in Mg; bukalna stran 3 Izolirani molarji М^ M, in M,; od spodaj Glej še tab. 14, si. 1,2 (lingvalna in zgornja stran istega primerka) Ontogenetic development of dentition in the cave bear 71 72_v Irena Debeljak Plate 16 Present-day brown bear; right mandible of a male approx. one and a half years old. Natural size (Found on 2 June 1992; killed by another bear). Kamenjak. Collection of the "Medved" breeding and hunting ground Kočevje 1 From above 2 Buccal side See also PI. 18, fig. 1 (lateral x-ray photograph of the same specimen) Tabla 16 Današnji rjavi medved; desna mandibula samca, starega okoli eno leto in pol. Naravna velikost (Najden 2. 6. 1992; ubit od drugega medveda.) Kamenjak. Zbirka Gojitvenega lovišča "Medved", Kočevje 1 Od zgoraj 2 Bukalna stran Glej še tab. 18, si. 1 (stranski rentgenski posnetek istega primerka) Ontogenetic development of dentition in the cave bear 73 74_v Irena Debeljak Plate 17 Cave bear; left mandible (invt. num. 1094) of a male approximately 4 years old. Divje babe I 1 Lingual side. Reduction 2:1 2 Detail: tooth row P4-M3 from above. Natural size See also PL 18, fig. 2 (lateral x-ray photograph of the same specimen) Tabla 17 Jamski medved; leva mandibula (inv. št. 1094) samca, starega približno 4 leta. Divje babe I 1 Lingvalna stran. Pomanjšano 2:1 2 Izsek: zobna vrsta P4-M3 od zgoraj. Naravna velikost Glej še tab. 18, si. 2 (stranski rentgenski posnetek istega primerka) Ontogenetic development of dentition in the cave bear 75 76_v Irena Debeljak Plate 18 1 Present-day brown bear; right mandible of a male approx. one and a half years old; lateral x- ray photograph (made at the Clinic for surgery and small animals of the Veterinary Faculty in Ljubljana). Natural size See also PL 16, fig. 1, 2 (upper view and buccal side of the same specimen) 2 Cave bear; left mandible (invt. num. 1094) of a male approx. 4 years old; lateral x-ray photo- graph (made at the Clinic for surgery and small animals of the Veterinary Faculty in Ljubl- jana). Natural size See also PL 17, fig. 1, 2 (lingual side and upper view of the same specimen) Tabla 18 1 Današnji rjavi medved; desna mandibula samca, starega okoli eno leto in pol; stranski rent- genski posnetek (izdelan na Kliniki za kirurgijo in male živali Veterinarske fakultete v Ljub- ljani). Naravna velikost Glej še tab. 16, si. 1,2 (zgornja in bukalna stran istega primerka) 2 Jamski medved; leva mandibula (inv. št. 1094) samca, starega približno 4 leta; stranski rent- genski posnetek (izdelan na Kliniki za kirurgijo in male živali Veterinarske fakultete v Ljubljani). Naravna velikost GEOLOGIJA 39, 79-90 (1996), Ljubljana Solenopora ladinica n. sp. und Solenopora suhadolica n. sp. (Rotalgen) und Paragondolella ? trammeri (Kozur, 1972) (Conodonta) aus dem Ladin (Mitteltrias) bei Suhadole, östlich von Ljubljana, Slowenien Solenopora ladinica n. sp. in Solenopora suhadolica n. sp. (rdeče alge) in Paragondolella ? trammeri (Kozur, 1972) (Conodonta) iz ladinija (srednji trias) pri Suhadolah, vzhodno od Ljubljane Anton Ramovš Katedra za geologijo in paleontologijo Univerza v Ljubljani, Aškerčeva 2, 1000 Ljubljana, Slovenija Schlüsselworte: Rotalgen, Konodonten, Ladin-Mitteltrias Ključne besede: rdeče alge, konodonti, ladinij - srednji trias Zusammenfassung Südw^estlich der Ortschaft Suhadole, östlich von Ljubljana, ist ein Riffkalk mit kleinen patch reefs von fächerförmigen, stark mit Kalk inkrustierten Rotalgen Solenopora ladinica n. sp. und Solenopora suhadolica n. sp. und mit kleinen patch reefs von phaceloiden Korallen Tropidendron rhopalifer Cruif, 1957 aufge- schlossen. Die umgebenden schwarzen Plattenkalke führen die Conodontenart Paragondolella ? trammeri (Kozur, 1972), die ladinisches Alter (Mitteltrias) des Riffkalkes beweist. Kratka vsebina Južnovzhodno od vasi Suhadole, vzhodno od Ljubljane, je razgaljen grebenski apnenec z majhnimi patch grebeni pahljačastih, močno z apnencem inkrustiranih rdečih alg Solenopora ladinica n. sp. in Solenopora suhadolica n. sp. in faceloidnih koral vrste Tropidendron rhopalifer Cruif, 1957. Opisani sta novi vrsti rdečih alg. V črnih ploščastih apnencih, ki obdajajo grebene, je ugotovljena konodontna vrsta Paragondolella ? trammeri (Kozur, 1972), ki dokazuje ladinijsko starost alginega in koralnega apnenca. 80 Anton Ramovš Einführung Südwestlich der Ortschaft Suhadole, östlich von Ljubljana befindet sich am linken Hang des Bučavnica-Baches ein massiger Riffkalk (Abb. 1). Der tektonisch zerklüftete und erosionsdeformierte Riffkalk-Körper erreicht in der Mitte seine grösste Mächtigkeit von 20 m und verjüngt sich nach beiden Seiten. Am Hang nördlich des Feldweges gibt es nur vereinzelte kleinere Vorkommen eines massigen Kalkes mit der grössten Mächtigkeit von 2 m. Auch nördlich und nordöstlich von der beschriebenen Lokalität sind vereinzelte kleine Riffkalk-Körper aufgeschlossen. Den mächtigsten Riffkalk-Körper baut ein schwarzer mikritischer bis fein- körniger, mit weissen Kalzitadern durchzogener Kalk auf. Sehr häufig sind kleine Hornstein-Körnchen vorhanden. Im tieferen und oberen Abschnitt des Riffkalk-Kör- pers sind Büschel von kleinen Korallen-Kolonien charakteristisch. Mehr oder weniger zahlreich sind Echinodermenreste, zarte Kalkschwämme (Inozoa) kommen häufig vor. Abb. 1. Die Lage des Fundortes der Rotalgen Solenopora ladinica n. sp. und Solenopora suhadolica n. sp. Sl. 1. Najdišče rdečih alg Solenopora ladinica n. sp. in Solenopora suhadolica n. sp. Solenopora ladinica n. sp. und Solenopora suhadolica n. sp. (Rotalgen) und ■.._83 Im unteren Teil des Riffkalk-Körpers kommen Exemplare der neuen Rotalge Solenopora ladinica n. sp. vor. Im mittleren und oberen Teil des Riffkalk-Körpers sind innerhalb des mikriti- schen Kalkes in Segmente geteilte fächerförmige, mit Kalk inkrustierte Thalli der neuen Rotalge Solenopora ladinica n. sp. charakteristisch. Sie bilden bis etwa 25 cm breite und ungefähr 20 cm hohe dicht beinander stehende Thalli. In anderen Kalkab- schnitten kommen Korallen-Büschel vor, bis etwa 20 cm lang und etwas weniger hoch. Korallen {Tropidendron rhopalifer Cuif, 1975) sind klein und umkristallisiert. Im Bereich des astförmigen Korallen-patch reefs kommen keine Rotalgen vor und umgekehrt. Äusserst selten treten Einzelkorallen vor, sie haben einen Durchmesser bis 1,5 cm. Schlecht ethaltene unbestimmbare Schalenreste und Echinodermenreste befinden sich in Bereich ohne Korallen und Rotalgen. Der Riffkalk ist vom schwarzen mikritischen Plattenkalk mit wechsellagernden dünnen mergeligen oder tonigen Lagen umgeben. Diese Kalke führen seltene Cono- donten mit der stratigraphisch wichtigsten Art Paragonodolella ? trammeri (Kozur, 1972), die auch das laninische Alter der Riffkalke beweist. Die neuen Solenoporen- und Korallen-Riffkalk-Körper hat Goce Mitrevski ent- deckt und mich auch zu der Fundstelle geführt. Dafür bin ich ihm sehr dankbar. Bekannte Solenoporen in der Mittel- und Obertrias in Slowenien Vereinzelte Solenopora sp.-Exemplare im massigen mittelanisischen Kalk am Schlossberg von Bled ähnelten nicht den Solenoporen von Suhadole. Sie bilden auch keine buildups (cf. Flügel et al., 1994, Taf. 2, Fig. 5-7). In Slowenien sind meines Wissens in den ladinischen Kalken keine riffbildenden Rotalgen bekannt. Im karnischen Riff von Hudajužna tritt die Gattung Solenopora nur mit einigen Thalli auf und spielt als Gerüstbildner keine besondere Rolle (Senowbary - Daryan, 1981, 112). Die unterkarnische Solenopora sp. von Mežakla, Mojstrana und Vitranc ähnelt im Wachstum der ladinischen Solenopora ladinica von Suhadole, ist jedoch nicht gesteinsbildend und kommt nur vereinzelt vor Sie hat auch eine viel feinere und ein- heitUche Struktur Im Thallus sind bis etwa 45 Zellenlagen (cf. Ramovš & Turnšek, 1984, 183, Taf. 10, Fig. 5). Solenopora alciformis Ott, 1966 vom Zatrep zwischen dem Kot-Tal und dem Vrata-Tal bildet kleine ramose Kolonien und ist mit den Soleno- poren von Suhadole nicht vergleichbar (cf. Ramovš & Turnšek, 1984, 183, Taf. 10, Fig. 6). Auch Solenopora sp. in den Jul/Tuval-Kalken von Pokljuka ist mit beiden Soleno- pora-Arten von Suhadole nicht vergleichbar (cf. Turnšek & Buser, 1989). Im Begunjščica-Gebirge, S-Karawanken, sind die Rotalgen durch die Art Soleno- pora styriaca Flügel, 1960 vertreten. Sie ist in typischer Form mit nodularen Thalli aus perlschnurförmigen Zellfäden entwickelt (Flügel & Ramovš, 1961, 291). Dieselbe Art ist in den Nor/Riffkalken in den nördlichen Julischen Alpen, am Splev- ta-Berg bekannt. Sie kommt nur vereinzelt vor und ist mit Solenoporaceen von Suhadole nicht vergleichbar (cf. Turnšek & Ramovš, 1987, 45, Taf. 15, Fig. 6). 82_Anton Ramovš Zur Bildung der Solenoporen buildups bei Suhadole Die kleine neue Solenopora ladinica ist nicht in Segmente gegliedert und bildet reguläre, kreisförmig angeordnete Zellenlagen. Sie sind ziemlich hoch. Es ist keine wesentliche Unterbrechung der Zellen-Lagen zu verfolgen. Kleine Hornstein-Körner haben stellenweise den Zellen wuchs verhindert. Auch bei der wesentlich grösseren, in Segmente gegliederten Solenopora suhadolica ist deutlich, dass die Zellenlagen nur mit kurzen Unterbrechungen gewachsen sind, eine Zellenlage folgte der anderen. Sie variiren in Höhe und Länge. Die charakteristischen paraleli angeordneten polygonalen Zellen-Lagen verlaufen im unteren Abschnitt der Segmente ununterbrochen und meist gleichmässig gewölbt. Im verbreiteten mittleren und oberen Teil der Segmente bilden sie meist höhere und niedrigere und untenschiedlich lange Zellenlagen. Gegen die senkrechten oder schrä- gen Segment-Grenzen keilen die Zellenlagen stumpf oder spitz aus. In den Solenoporen buildups bei Suhadole kann man keine Wechsellagerung von organischen und sedimentären Lagen beobachten. Der Wuchs von kleinen Soleno- poren-patch reefs ist nicht unterbrochen worden. Zeitweise hat sich während des Wuchses mechanische oder biologische Erosion manifestiert. In einigen Segmenten haben Anhäufungen von Mikrofossilien und- oder vom Feindetritus zwischen den Solenoporen-Zellenlagen den Algenwuchs kurz unterbrochen. Bei dem Bau der beschriebenen Solenoporen-buildups haben sich Cyanobacterien als stromatolithen- bildende Organismen nicht beteiligt. Die Solenoporen-Zellenlagen-Struktur ist in meistens weissen und teilweise auch in grauen Teilen der buildups noch deutlich erhalten. In den jetzigen dunkelgrauen und schwarzen, meist mittleren Teilen der Zellenla- gen ist die Zellenstruktur durch diagenetische Vorgänge vernichtet. Die Diagenese hat in vereinzelten Abschnitten manchmal unregelmässig zwei oder mehr Zuwachs- zonen in Mikrit umgewandelt (unregelmässige schwarze Felder, Abb. 5a, 5b). Wendt (1993) hat sich eingehend mit "Solenoporacean Stromatolites" beschäftigt. Er beschreibt Collenella sp. A aus dem Oberperm von Djebel Tebaga, Tunesien, und Collenella sp. B aus dem unteren Kam von Denti di Terrarossa, Dolomiten, Italien. Beide stellen wahrscheinlich zwei neue Arten dar, er hat jedoch beide Formen als Collenella sp. A und Collenella sp. B dargestellt. Wendt (1993, 108, 109) beschreibt auch die Geschichte der Collenella-Unter- suchungen, erstmals von Johnson (1963) beschrieben. Er konnte im Material von der Typus-Region keine Mikrostruktur nachweisen. Er kam jedoch zum Schluss, Col- lenella guadalupiensis sei ein "Solenoporacean Stromatolit", "in which the algal cell structure is totaly obliterated by diagenesis". Er schreibt: "Therefore it can be speculated that the rhytmic growth of the solenoporacean stromatolites reflects annual oscillation of muddy influx over period- ically re-established algal mats. Newertheless these stromatolites do not fit into a simple model of regularly alternating organic and sedimentary layers (Wendt, 1993, 107). In den Solenoporen buildups von Suhadole sind keine Stromatoliten-Lagen vorhanden. Es handelt sich nur um Solenoporen buildups. Mineralogische Untersuchungen der Solenoporen-Lagen brachten folgende Ergebnisse: "x-ray diffraction measurement: only calcite mineral was detected. Aragonite mineral was not proved". Solenopora ladinica n. sp. und Solenopora suhadolica n. sp. (Rotalgen) und ■.. 83 Systematische Paläontologie Rhodophyta Wettstein, 1901 Familie Solenoporaceae Pia, 1927 Unterfamilie Solenoporoidae Maslov, 1935 Gattung Solenopora Dybowsky, 1878 Typische Art Solenopora spongioides Dybowsky, 1878 Solenopora suhadolica n. sp. Abb. 2, 3 Derivatio nominis: ladinica, nach dem ladinischen Alter des Fundortes. Holotypus: Abb. 2. Paläontologische Sammlung des Lehrstuhls für Geologie und Paläontologie der Universität Ljubljana, Katalognummer 5330. Abb. 2. Solenopora ladinica n. sp. Holotypus. Suhadole, KGP Nr. 5330, Gesteinsstück, Oberfassan, Ladin, Mitteltrias, x 1,5 Sl. 2. Solenopora ladinica n. sp. Holotip. Suhadole, KGP št. 5330, kamninski kos, zgornji fassan, ladinij, srednji trias, x 1,5 84 Anton Ramovš Abb. 3. Solenopora ladinica n. sp. Paratypus. Suhadole, KGP Nr. 5330 a, Dünnschliff, Oberfa- ssan. Ladin, Mitteltrias, x 5 Sl. 3. Solenopora ladinica n. sp. Paratip. Suhadole, KGP št. 5330 a, zbrusek, zgornji fassan, ladinij, srednji trias, x 5 Stratum typicum: Riffkalk-Körper südwestlich der Ortschaft Suhadole, östlich von Ljubljana. Locus typicus: Nordöstlicher Hang des Bučavnica-Baches, südwestlich der Ortschaft Suhadole, östlich von Ljubljana. Diagnose: Thalus aufrecht, seitlich fächerförmig, nicht segmentiert, mit kon- vexen konzentrischen Zuwachszonen. Dicht beieinander stehende Zellen sind poly- gonal. Thalus ist mit Kalk inkrustiert. Beschreibung: Die Basis des Thallus kreis- bis ellipsenförmig und knollig verdickt. Der Thallus ist bis etwa 3 cm hoch und 2 cm breit. Die konvexen Zuwachs- zonen sind verhältnismässig stark ausgebildet. In den beobachteten Exemplaren kommen auf 3 cm Höhe 10 bis 11 Zellenlagen vor. Sie sind etwa gleich stark in ganzer Höhe und in regelmässigen Abständen angeordnet. Im angewitterten Zustand sind zwischen den halbkreisförmigen erhöhten Teilen ziemlich tiefe Furchen. Solenopora ladinica n. sp. und Solenopora suhadolica n. sp. (Rotalgen) und ■.._87 Beziehungen: Solenopora ladinica stellt eine ältere und einfachere Form der ladinischen Rotalgen im Fundort Suhadole dar Sie leitet über zu den segmentierten Formen der ladinischen Solenopora, welche auch viel grösser ist. Solenopora ladinica kommt überwiegend im unteren Abschnitt des Riffkalk-Körpers von Suhadole vor. Im höheren Riffkalk-Bereich kommt sie nur noch vereinzelt vor Im oberen patch reef beobachtet man nur noch grosse, segmentierte Solenopora suhadolica. Solenopora ladinica unterscheidet sich wesentlich von der Gattung Collenella (Johnson, 1963, 136-137) aus dem Oberperm der Guadalupe Mountains in Nor- damerica. Auch mit Collenella sp. A im tunesischen Oberperm und Collenella sp. B im Unterkam der Dolomiten (Wendt, 1993, Fig. 2 und Fig. 3) ist sie nicht vergleichbar Solenopora suhadolica n. sp. Abb. 4, 5a, 5b Derivatio nominis: nach dem Fundort Suhadole genannt. Holotypus: Gesteinsstück. Abb. 4, 5a, 5b. Paläontologische Sammlung des Lehrstuhls für Geologie und Paläontologie der Universität Ljubljana. Katalog- Num- mer 5331. Stratum typicum: Riffkalk-Körper südwestlich der Ortschaft Suhadole, östlich von Ljubljana. Locus typicus: Nordöstlicher Hang des Bučavnica-Baches, südwestlich der Ortschaft Suhadole, östlich von Ljubljana. Diagnose: Thallus aufrecht, breit fächerförmig, stark in Segmente gegliedert mit nach oben verschieden breiten, konvexen, konzentrischen, verhältnissmässig schmalen, einander folgenden Zuwachszonen mit polygonalen Zellen. Thallus mit Kalk inkrustiert. Beschreibung: Die Basis des Thallus kreis- bis ellipsenförmig und knollig verdickt. Der aufrechte Thallus verbreitet sich stark fächerförmig, ist in Segmente geteilt mit leicht konvexen Zuwachszonen. Zwischen den Segmenten verlaufen ver- tikale oder schräge Furchen. Im Abstand von 4 cm kommen bis etwa 20 Zellenlagen vor Sie sind etwa gleich stark bis unterschiedlich hoch und in regelmässigen Abstän- den angeordnet. Der Thallus kann eine Höhe bis etwa 20 cm und eine Breite von 25 cm erreichen. Ini Thallus treten manchmal kleine schwarze Hornstein-Körnchen auf, die das Wachstum der Zellenlagen verhindert haben. Beziegungen: Solenopora suhadolica unterscheiden sich von Solenopora ladini- ca durch beträchtliche Grösse, durch einen viel komplizierter gebauten, stark segmen- tierten Thallus. Solenopora suhadolica hat sich aus der primitiven Solenopora ladini- ca entwickelt. Solenopora suhadolica zeigt in der Morphologie der Zellen-Lagen und im Zellenbau eine Ähnlichkeit mit der unterladinischen Collenella sp. vom Cipit boul- der, Denti di Terrarossa, Dolomiten, Italien (Wendt, 1993, 106, Fig. 3). 86 Anton Ramovš Abb. 4. Solenopora suhadolica n. sp. Holotypus. Suhadole, KGP Nr. 5331, Gesteinsstück, Oberfassan, Ladin, Mitteltrias Sl. 4. Solenopora suhadolica n. sp. Holotip. Suhadole, KGP št. 5331, kamninski kos, zgornji fassan, ladinij, srednji trias Abb. 5a. Solenopora suhadolica n. sp. Holotypus. Suhadole, KGP Nr. 5331, Dünnschliff vom Holotypus. Vier Segmente mit aneinander folgenden Solenoporen-Zellenlagen. In den unter- schiedlich ausgebild^eten weissen und hellgrauen Zellenlagen ist die Struktur noch erhalten. In den schwarzen Zellenlagen und in unregelmässigen Partien (Feldern) hat eine feine Kalzit- Kristallisation die Zellenlagen-Struktur umgewandelt. Im ersten und zweiten Segment von links sind in weissen Abschnitten Anhäufungen von Mikrofossilien und Feindetritus, x 5 Sl. 5a. Solenopora suhadolica n. sp. Holotip. Suhadole, KGP Nr 5331, zbrusek holotipa s štirimi segmenti solenoporskih celičnih plasti. V različno oblikovanih belih in svetlo sivih celičnih plasteh je še ohranjena struktura. V črnih celičnih plasteh in v nepravilnih delih segmentov je kalcitna kristalizacija spremenila algino celično strukturo. V prvem in drugem segmentu od leve so v belih delih mikrofosili in droben detritus, x 5 Solenopora ladinica n. sp. und Solenopora suhadolica n. sp. (Rotalgen) und ■.._89 Stamm Conodonta Eichenberg, 1936 Oberfamilie Gondolellacea Lindstöm, 1970 Familie Gondolellidae, Lindström, 1970 Gattung Paragondolella Mosher, 1968 Typusart Paragondolella excelsa Mosher, 1968 Paragondolella ? trammeri (Kozur, 1972) 1972 Gondolella haslachensis trammeri Kozur n. subsp. - Kozur und Mock, S. 13, Taf. 1, Fig. 3-5, non Fig. 5, 7. 1980 Gondolella trammeri Kozur emend. - Kovács und Kozur, S. 58, Taf. 6, Fig. 6, 8, non Fig. 7. 1983 Gondolella trammeri Kozur, 1971 (corr. A. R. 1972). - Krystyn, S. 239, Taf. 1, Fig. 5, Taf. 2, Fig. 5-6, Taf. 3, Fig. 3, 4. Material: Zwei Exemplare. Original-Diagnose: Kozur und Mock, 1972, S. 13. Beschreibung: Ramovš, 1994. Zum Alter: Paragondolella ? trammeri nach Original-Beschreibung kommt in der curionii-Zone (Oberfassan) und im unteren Longobard der südalpinen Sub- provinz der austroalpinen Conodonten-Provinz vor Stratum typicum ist eine Ammonitenbank mit Eoprotrachyceras curionii und Proarcestes (Kozur & Mock, 1973, 13), die der obersten curionii-Zone angehört. In der Tafel-Beschreibung von G. trammeri emend. (Kovács & Kozur, 1980, S. 58, Taf. 6, Fig. 6-8) ist das Alter unteres Longobard, M. hungaricus A.-Z. Nach Krystyn (1983, 239) zählt G. tram- meri im Epidaurus-Profil zu den wichtigsten Leitformen und hat sich im Grenzbe- reich Anis/Ladin aus G. eotrammeri entwickelt. Alter des Rotalgen-Kalkes: Oberfassan, Budurovignathus truempyi A.Z. (von Kozur, 1989, S. 394 aufgestellt). Astförmige Conodontenelemente Paragondolella ? trammeri, der einzige gefundene Plattformconodont in den schwarzen Plattenkalken bei Suhadole, ist von folgenden astförmigen Elementen begleitet: cypridodelliformes Element, enantiognathiformes Element, hindeodelli- formes Element, ozarkodiniformes Element und prioniodiniformes Element. Abb. 5b. Neunfache Vergrösserung des mittleren Abschnittes des dritten Segmentes von Abb. 5a. In weissen und grauen Zellenlagen sind Lagen mit dicht aneinander stehenden Zellen sicht- bar In schwarzen Feldern ist die Kalzit-Kristallisation erkennbar Sl. 5b. Devetkratna povečava srednjega dela tretjega segmenta pete slike. V belih in sivih celičnih plasteh so vidne tesno stoječe algine celine. V črnih poljih je razpoznavna kalcitna kristalizacija Vse fotografije M. Grm 90__Anton Ramovš Andere Mikrofossilreste In den Conodontenproben gibt es auch vereinzelte Steinkerne von Foraminiferen und juvenilen Ammoniten. Vereinzelt kommen Reste von Schwebcrinoiden und Fischzähnchen vor. Zahlreich sind Radiolarien- und Spongien-Reste. Danksagung Dr. Ivka Munda, Forschungszentrum der Slowenischen Akademie der Wis- senschaften und Künste danke ich für aufschlussreiche Diskussion und grundlegende Literatur sowie Herrn Prof. Dr Jost Wendt, Geologisch-Paläontologisches Institut der Universität Tübingen für wichtige Literatur und Herrn Prof. Dr. Robert Riding, Department of Earth Sciences Cardiff, für kritische Bemerkungen. Schriftum Flügel, E. & Ramovš, A. 1961: Fossilinhalt und Mikrofazies des Dachsteinkalkes (Ober- Trias) im Begunjščica-Gebirge, S-Karawanken (NW-Slowenien, Jugoslawien. - N. Jb. Geol. Palönt., Mh., 287-294, Stuttgart. Flügel, E., Ramovš, A. & Bucur, I.I. 1993: Middle Triassic (Anisian) Limestones from Bled, Northwestern Slovenia: Microfacies and Microfossils. - Geologija 36 (1993), 157-181, Ljubljana. Johnson, J. H. 1963: Pennsylvanian and Permian algae. - Quart. Colorado School Mines 58, No 3, 211 S., Golden, Colorado. Kovács, S. & Kozur, H. 1980: Stratigraphische Reichweite der wichtigsten Conodonten (ohne Zahnreihenconodonten) der Mittel- und Obertrias. - Geol. Paläont. Mitt. Innsbruck 10, 47-78, Innsbruck. Kozur, H. 1989: Significance of events in conodont evolution for the Permian and Triassic stratigraphy. Courier Forsch.-Inst. Senckenberg 117, 385-408, 1 Fig., 7 Tabs., Frankfurt/M. Kozur, H. & Mock, R. 1972: Neue Conodonten aus der Trias der Slowakei und ihre strati- graphische Bedeutung. - Geol. Paläont. Mitt. Innsbruck 2, 1-20, Innsbruck. Krystyn, L. 1983: Das Epidaurus-Profil (Griechenland) - ein Beitrag zur Conodonten- Standardzonierung des tethyalen Ladin und Unterkam. - Schriftenreihe Erdwiss. Komm., Österr. Akad. Wiss. 5, 231-258, 8 Taf., Wien, New York. Ramovš, A. 1994: Oberfassanische (mitteltriassische) Conodonten aus Kalken südlich von Slugovo, Südslowenien. Geologija 37/38, 141-151, Ljubljana. Ramovš, A. & Turnšek, D. 1984: Lower Carnian reef buildups in the northern Julian Alps (Slovenia, NW Yugoslavia). - Razprave IV. razr SAZU 25, 161-200, 15 Taf., Ljubljana. Senowbary - Daryan, B. 1981: Zur Paläontologie des Riffes innerhalb der Amphycli- nen-Schichten bei Hudajužna, Slowenien. - Razprave IV. razr. SAZU 23, 99-118, 10 Taf., Ljub- ljana. Turnšek, D. & Buser, S. 1989: The Camian reef complex on the Pokljuka (NW Yugoslavia). - Razprave IV. razr. SAZU 30, 75-127, Ljubljana. Turnšek, D. & Ramovš, A. 1987: Upper Triassic (Norian-Rhaetian) reef buildups in the northern Julian Alps (NW Yugoslavia). - Razprave IV. razr SAZU 28, 27-67, 16 Taf., Ljubljana. Wendt, J. 1993: Solenoporacean Stromatolites. - Palaios 8, 101-110, Tulsa/OK. GEOLOGIJA 39, 91-95 (1996), Ljubljana Pironaea buseri n. sp. from olistostromal breccia of Paleocene flysch by Anhovo Desanka Pejović Simina 19, 11000 Beograd, Yugoslavia Key words: Hippuritidae, Pironaea, taxonomy, chaotic breccia, Soča Valley, Slovenia Abstract A new species, Pironaea buseri, found in chaotic breccia in Paleocene flysch beds in the wider region of the Soča valley, is ascribed to the genus Pironaea Meneghini. The large L-S distance and equal L-S and E-S spacings distinguish the new species from any known pironaea species. The species was found with Vaccinites giordani (Pirona) and Hippuritella cornucopiae (Defranee). Introduction In the chaotic limestone breccia of the Podbrdo cyclotheme within the Paleocene flysch Jože Fekonja years ago found in the Rodež quarry at Anhovo (Fig. 1) a well preserved sample of sorted out incomplete right valve of a pironaea that was stored by Miklavž Fajgelj in the collection of rocks from the quarry. Shortly afterwards Dr Stanko Buser found in a similar chaotic breccia in flysch not far from the pironaea find on the crest between the quarries Lastivnica and Deskle the rudists Vaccinites giordani (Pirona) and Hippuritella cornucopia (Defranee). The mentioned rudist fauna was ceded to me by Stanko Buser for paleontologie examination for which I am very grateful to him. The rudists were redeposited during the forming of Paleocene flysch as isolated specimens into the flysch basin from the southerly lying Diñarle carbonate platform. Owing to their position within the impermeable flysch marls, the isolated rudists were not lithified in the chaotic breccia nor firmly glued to its limestone fragments, and were therefore well suited for palaeontologic study. It is interesting to note that previously nowhere in Slovenia pironaeas and the species Vaccinites giordani were found in primary position in the Upper Cretaceous limestone, but only redeposited in younger flysch beds. This permits the supposition that these rudist species were asso- ciated with a narrow living environment on the northern rim of the Diñarle carbon- ate platform that was redeposited into the flysch basin during the time of its disinte- gration (B u s e r et al., 1988; B u s e r et al., in press). 92 Desanka Pejović Fig. 1. Location map of Pironaea buseri n. sp. Ov^^ing to the extremely well preserved internal characteristics, and owing to the fact that the pironaea found in Anhovo in the Soča valley differs from all pironaeas found so far, the fossil was attributed to the new species Pironaea buseri. Systematic palaeontology Hippuritidae Gray, 1848 Pironaea Meneghini, 1868 Pironaea buseri n. sp. PI. 1, Fig. 1 Derivation of name: The species is dedicated to Professor Stanko Buser, Uni- versity in Ljubljana. Holotype: Transverse section of the right valve shown in PI. 1, Fig. 1, sample no 158, author's collection of rudists, Belgrade. Type locality and stratigraphie position: The quarry of Rodež near Anhovo; redeposited in Paleocene flysch. Material studied: Only one incomplete specimen of the right valve. Pironaea buseri n. sp. from olistostromal breccia of Paleocene flysch by Anhovo_^ Diagnosis: Right valve externally ribbed longitudinally, ribs separated by a narrov^ furrow. Outer shell layer thin. Ligamental ridge and pillars radially posi- tioned to each other. Ligamental ridge and the second pillar almost equal in length. L-E distance takes approximately one-third of valve circumference; L-S and S-E dis- tance equal. Secondary folds of the first cycle well developed and narrower at base; secondary folds of the second cycle distinctly marked, nonuniform in shape. Description: The found fragment of a right valve is 5cm long; its anterior-pos- terior and dorsal-ventral diameters are 10.5 cm and 11cm, respectively. The part of the right valve to which the fragment belonged is impossible to identify, but seems to be the central part. It shows externally large longitudinal ribs 1 cm wide, separated by narrow furrows equivalent to internal folds. Each rib shows two or three secon- dary ribs. Plicated growth lines are distinct. Internal features are not distinguishable in the three successive transverse sections, i.e. ontogenetic changes are not detectable. The outer shell layer is relatively thin (about 3 mm) in relation to the valve size. Ligamental ridge is long, wide at the top and narrow at base and slightly bent away from the first pillar. The first pillar is droplike, narrow at base like a stem. The sec- ond pillar is longer than the first pillar and insignificantly longer than the ligamental ridge, almost uniform in thickness through the length, radially positioned and very slightly curved at top to the first pillar. It clearly shows facing sheets of the outer shell layer. L-E distance is large, greater than in any known pironaea species; it takes almost a third of the valve circumference. L-S and S-E distances are equal. Secon- dary folds of the first cycle, 11 in number, are well developed and equally long, widening distally and narrow at base, they look like drops. They distinctly show the facing line of two outer shell layer sheets. Secondary folds of the second cycle are well marked, 12 in number, unequal in size, mostly half shorter than those of the first cycle. They also show the facing line of the outer shell layer sheets. Three secondary folds between ligamental ridge and the first pillar, and three between the first and the second pillars, are arranged so that the first cycle fold is in the middle and a sec- ondary fold of the second cycle on its either side. Remarks: The large L-E distance and equal L-S and E-S spacings, and the shapes of pillars and ligamental ridge, distinguish sufficiently Pironaea buseri n. sp. from any known pironaea species. The new species resembles Pironaea machnitschi Wiontzek (Wiontzek, 1933, p. 10, Fig. 1) in having larger siphonal zone, or the L-S spacing, and in certain similarities of shape and position of E and S pillars and the ligamental ridge. However, L-S distance in the latter species is half that of S-E, whereas L-S and S-E distances are equal in the new species. Also, the shape and number of secondary folds of the first and second cycles clearly differ in the two species. Secondary folds of the first cycle are forking in the proximal end in Pironaea machnitschi, and are simple in the new species. Besides, the configuration of secon- dary folds is also different: it is regular in Pironaea buseri, i.e. one fold of the first cycle between two folds of the secondary cycle, and in Pironaea machnitschi two folds of the first cycle are next to each other. In the shape of ligamental ridge, and in the shape but not the number of secon- dary folds of the first and second cycles, the new species has some resemblance to the species Pironaea fruscagorensis Milovanovic, Sladic, Grubić. However, the L-E dis- tance in P. fruscagorensis is even smaller than that of L-S or S-E in the new species; moreover, secondary folds are lacking in the siphonal zone. If the moniliform nature of folds in Barrettia, and not only this genus because it 94_Desanka Pejović was also noted in some pironaeas {Pironaea milovanovici Kühn, P. postdalmatinica Pamouktchiev, P. milovanovici quatretondaensis Philip), was a secondary phenome- non, as I suggested as a possibility (Pejovic, 1988; Pejović, in press) and con- firmed on some caprinids (Pejovic, 1972, p. 367-368, Figs, a-d), the new species would be also comparable with Barrettia monilifera Woodward from Flor de Alba Limestone, Puertorico (Van Dommelen, 1971, p. 113, PL X, Fig. 1). The L-S dis- tance in this specimen is almost identical with that of the new species Pironaea buseri. Also, the number and distribution of secondary folds between L and S, and S and E, which are not even moniliform, neither the first and second pillars are identi- cal with respective folds of the new species. References Buser, S., Pe j ovi Ć, D. & Radoičić, R. 1988: Redeposited Rudists in Senonian and Pale- ocene Flysch Beds in the wider Region of the Soča Valley. - First International Conference on Rudists, October 1988, Abstracts, p. 3, Belgrade. Buser, S., Pejović,D. & Radoičić, R. 19 : Redeposited Rudists in Senonian and Pale- ocene Flysch Beds in the wider Region of the Soča Valley. - Proc. Intern. Conf. on Rudists (Belgrade, October 1988), Serb. Geol. Soc., Spec. Pubi, (in press). Pej ović, D. 1972: On the Phenomenon of "Rosary" in the external Layer of the Caprinidae Shell. - Bulletin scientifique. Sect. A, Tome 17, No 11-12, Zagreb. Pejović, D. 1988: On Radiolitidae and Hippuritidae Shell Structure. - First International Conference on Rudists, October 1988, Abstracts, p. 18, Belgrade. Pejović, D.: Sur la structure du test des Radiolitidae et Hippuritidae. - Proc. Intern. Conf. on Rudists (Belgrade, October 1988), Serb. Geol. Soc., Spec. Pubi, (in press). VanDommelen, H. 1971: Ontogenetic, Phylogenetic and Taxonomic Studies of the Amer- ican Species of Pseudovaccinites and of Torreites and the Multiple-fold Hippuritids. - Thesis, University of Amsterdam, 1-125, Amsterdam. Wiontzek, H. 1933: Rudisten aus Oberen Kreide des Mittleren Isonzogebietes. - Palaeon- tographica, 80, A, Stuttgart. Pironaea buseri n. sp. from olistostromal breccia of Paleocene flysch by Anhovo 95 Plate 1 1 Pironaea buseri n. sp., Rodež by Anhovo Holotype, transverse section of right valve, sample no 158, natural size GEOLOGIJA 39, 97-118 (1996), Ljubljana Pseudosocka Beds with Coal in Borehole Tdp-1/84 Trobni Dol (Eastern Sava Folds, Slovenia) Psevdosoteške plasti s premogom v vrtini Tdp-1/84 Trobni Dol (vzhodne Posavske gube) Karel Grad, Stevo Dozet, Rajko Petrica & Lija Rijavec Geološki zavod Ljubljana Inštitut za geologijo, geotehniko in geofiziko Dimičeva 14, 1000 Ljubljana, Slovenija Key-words: coal, chemistry, stratigraphy, tectonics. Upper Oligocene, Miocene, eastern Sava Folds, Slovenia Ključne besede: premog, kemična sestava, stratigrafija, tektonika, zgornji oligocen, miocen, vzhodne Posavske gube, Slovenija Abstract The sedimentary succession with coal in the Trobni Dol area was studied in detail. The coal district lies east of Laško and belongs to the eastern part of the Sava folds. Every attention was given to the stratigraphie problems of the Egerian succession as well as to the coal, his stratigraphie position and age. The Pseu- dosocka beds are subdivided into the lower Pseudosocka beds, the coal horizon and the upper Pseudosocka beds. The coal seams of the Trobni Dol sedimentary succession were formed in the Upper Oligocene, the Lower Egerian respectively. Finally, the correlation of the Pseudosocka beds from Trobni Dol and western Laško synclinorium area was performed. Kratka vsebina Na območju Trobnega Dola smo podrobno raziskali zaporedje sedimentnih kamnin z vložki premoga in piroklastitov. Trobnodolski premogovni bazen leži vzhodno od Laškega na ozemlju, ki geotektonsko pripada vzhodnim Posavskim gubam. Glavno pozornost smo posvetili stratigrafskim problemom egerijskega sedimentacijskega zaporedja, zlasti pa premogu, njegovi stratigrafski legi in staro- sti. Psevdosotešfc plasti smo razčlenili v spodnje Psevdosoteške plasti, premogov- ni horizont in zgornje Psevdosoteške plasti. Sloji premoga v trobnodolskem sedi- mentnem zaporedju so se oblikovali v zgornjem oligocenu oziroma spodnjem egeriju. 98 Karel Grad, Stevo Dozet, Rajko Petrica & Lija Rijavec Introduction Geologie investigations in the Trobni Dol area were carried out in the frame of the coal exploration programme in Slovenia. The scope of these investigations was to study the geology of the abandoned Trobni Dol and Pojerje coal mines as well as the area between Trobni dol, Breze and Pojerje (Fig. 1). With this purpose about 16 km^ of the terrain among Breze, Trobni Dol and Pojerje was mapped in detail (Petrica, Fig.l. Location sketch map SI. 1. Položajna karta Pseudosocka Beds with Coal in Borehole Tdp-1/84 Trobni Pol_101 1984). In the year 1984 two deep exploration boreholes were bored west and north of the abandoned coal mine Trobni Dol. For understanding the lithostratigraphic condi- tions of the wider area the borehole Tdp-1/84 with the depth of 385 metres reaching the Tertiary basement is important. Due to tectonic conditions the second borehole (Tdp-2/84), being bored up to 400 m, did not reach the Pre-Tertiary basement. Further on, the area between Lahomno and Grahovo was reconnoitred for the scope of underground gas storage construction by S. Dozet, P. Mioč, M. Žnidarčič, B. Stojanovič and M. Demšar (Mioč et al., 1983). The Rudnica anticlinal area was explored for the same purpose by S. Dozet and B. Stojanovič (Dozet, 1985). Simultaneously with the geological mapping the sampling of the Tertiary rocks and coal was performed. The Tertiary microfauna was determined by Rijavec (1983, 1984 a, b, c). Pétrographie analysis of the Oligocene and Miocene rocks was carried out by Orehek and Kovič (1984). X-ray analysis was done by Mišič (1984). Chemical analysis of the coal samples was executed in the laboratory of REK Trbovlje by T. Žuža. The Tertiary macrofauna was revised by V. Mikuž. Previous investigations In the past the wider area of Trobni Dol was investigated many times owing to the coal and other mineral resources. A great number of printed and manual works exist on these investigations. The Zollikofer's decription of the Tertiary beds among Konjiška gora, Macelj, Sotla and Savinja was one of the first and most important geological works. This work was the basis for the Bittner's and other subdivisions of the Tertiary in this area. Zollikofer (1861) ranged the coal-bearing beds at Zagorje and Trbovlje as well as their continuation to the east of Laško to the oldest Neogene. Stur (1871) described the Neogene beds of the wider area. As Socka beds he considered all continental strata of the region Socka-Trbovlje-Zagorje lying between the Triassic basement and the Marine marly clay. He noticed that the Socka beds of Laško originated in the fresh-water environment and that towards the east a brackish and a marine fauna prevails. Bittner (1884) divided the Tertiary beds between Laško and Zagorje into the "Socka" beds with coal, the marine Miocene beds (Marine clay and green sands, the lower Leitha limestone, the Laško marl and the upper Leitha limestone) as well as the brackish Sarmatian beds. Granigg (1910) noticed that the coal mine Trobni Dol lies in the southern limb of the Laško synclino- rium. He mentioned a 72 cm thick coal seam which contains a 37 cm thick clay interbed. He ranged the beds with coal into the Govce beds. In the period between both wars the study area was explored by A. Winkler, M. Munda and W. Petrascheck. Petrascheck (1926/29) distinguished two horizons of coal: a) - older, from the limnic and brackish "Socka" beds and b) - younger from the Aquitanian marine beds. Munda (1939, 1942, 1953) correlated the "Socka" beds of Senovo, Trobni Dol, Zagorje, Medvode and Bohinj. He mentioned that the Trobni Dol coal formation, can not be of Miocene age taking into account its fossil contents. The period of most intensive geological investigations occurs after the Second World War with appereance of the following researchers: M. Hamrla, M. Munda, K. Grad, A. Nosan, D. Kuščer, L. Rijavec and others. Hamrla (1954, 1955, 1987) observed that the Laško Tertiary coal seam was getting thinner in the west-east direction. He considered that simultaneously with the predominant marine develop- ments of the Oligocene beds in the east direction, conditions for formation of coal 100_Karel Grad, Stevo Dozet, Rajko Petrica & Lija Rijavec were less favourable. In short brackish intervals only thin coal seams can be formed. Grad (1962, 1967) gave a geologic outline of the Kozje area. Among Tertiary beds he mentioned the Oligocene, Badenian and Sarmatian ones. He considered the main folding in the area to be Post-Pannonian. Nosan (1956) distinguished three facial types of the "Socka" beds: a) - the "Socka" beds at Zagorje-Hrastnik-Trbovlje, b) - the "Socka" beds in the Senovo basin and, c) - the "Socka" beds between Pohorje and Bohor. Kuščer (1962, 1967) ascertained that in the Lasko-Zagorje synclinorium occurs only one coal seam in the "Socka" beds. The coal passes downwards into a black shaly clay (black footwall) and upwards gradually into the light brown marly lime- stone and shale with sandy intercalations. Rijavec (1959, 1965, 1974, 1983, 1984a, b, c, 1986) determined the Tertiary microfauna in the following areas: Rudnica and Boč, Loka at Žusem, Šmarje at Jelše as well as the Trobni Dol and its wider sur- roundings. She determined the microfauna from the surface and both boreholes of Trobni Dol. The detailed investigations for the Geological map of Slovenia, the map sheet Ce- lje on the scale of 1:100 000 with corresponding explanatory text written by Buser (1979) are of great importance. The author combined the results of the geological mapping and reconnaissance in the Celje map sheet area a detailed description of the mapping units. He attributed the main folding of the study region to Helvetian. Lately, R. Petrica et al., P. Mioč et al., S. Orehek et al., P. Kovic, M. Mišic, S. Dozet et al., G.S. Odin et al. and M. Jelen et al. contributed to the interpretation and expla- nation of geologic problematics of the area. Mioč et al. (1983) reported on results of geological and geophysical explorations in the Šmarjeta-Lahomno area. Mišič (1984) analysed with X-ray method the volcanic succession from the borehole Tdp- 1/84 in the hanging wall of the "Socka" beds. Jelen (1984) examined palinologically samples of the Oligocene marine clay and the "Socka" beds from the borehole Tdp- 1/84. Dozet (1985) and Dozet et al. (1994) reported on results of the geological investigations in the Rudnica anticline area. Dozet and Rijavec (1994) described geological conditions in the area of Šentjur-Planina-Trobni Dol-Loka at Žusem. Ko- vič (1984, 1985) described and sistematically classified Tertiary rocks of the Trobni Dol area by means of microscopic examination of thin sections. Jelen et al. (1990) described changes of the Oligocene microfossil assemblages in the Zagorje region. Jelen et al. (1992, 1994) established that the "Socka" beds in the southern Kara- vanke and Socka area are of Middle and Upper Eocene age. Since the beds with coal in the area between Laško and Zagorje are of Oligocene age, they considered the Socka beds as Pseudosocka beds. Odin et al. (1994) presented the results of geochronological analysis of pyroclastic interbeds in the coal from Neža (Trbovlje). The analytical results indicate that the plagioclase samples were erupted at 25 ± 1.0 Ma (2a), therefore the Pseudosocka volcanoclastic layers containing the plagioclase were deposited during the Late Chattian. Petrica et al. (1995) described strati- graphy of the Upper Oligocene and Miocene beds in the Trobni Dol area. Geographic setting The Trobni Dol and Pojerje coal mine areas are situated in the eastern Sava folds 10 km east of Laško and 8 km south of Šentjur This is the area of up to 800 metres Pseudosocka Beds with Coal in Borehole Tdp-1/84 Trobni Pol_103 high narrow elevations of west-east direction as well as of steep and narrow valleys being formed by faulting and stream erosion. The access to the investigated area is possible through the Lahomnica valley from the Laško direction, along the Gračnica valley (Jurklošter, Marof) from the Rimske Toplice direction, as well as from the Šentjur direction passing across Breze. Geology of the area Pre-Tertiary basement The Pre-Tertiary basement is exposed only along contacts with the Tertiary suc- cession. Most of Tertiary overlies erosively and discordantly the Permo-Carbonifer- ous micaceous shales, quartz sandstones and conglomerates. South of V. Grahovše and in the close vicinity of the abandoned Trobni Dol coal mine crop out Permo-Car- boniferous rocks and Triassic dolomite underlying the Tertiary beds. The other part of the Pre-Tertiary basement is probably built up from the Permian sandstones. Mid- dle Triassic Pseudozilian shales and kerathophyre tuff as well as the Triassic dolomi- te, which are in tectonic contact with the Tertiary rocks at northern and southern edge of the investigated area. Stratigraphie and tectonic relationships of the Pre-Tertiary rocks were not stud- ied by us. Tertiary In the investigated area the Tertiary succession begins with the Upper Oligocene Pseudosocka beds, which lie discordantly upon the Triassic dolomite. Upwards fol- low grayish green Marine marly clay, green dacitic tuff and repeatedly clayey beds belonging to Egerian and passing upwards into the Govce beds. Discordantly upon the Govce beds rests the Badenian (Tortonian) succession which is discordantly over- lain by the Sarmatian sediments. The complete development of the Tertiary beds is similar to the Tertiary developments in other parts of the Laško synclinorium. Upper Oligocene In the study area the Oligocene comprises the Pseudosocka beds, grayish green Marine marly clay and dacitic tuff. In this paper the Pseudosocka beds from the bore- hole Tdp-1/84 are considered in detail. According to S tur (1871) the beds at Socka (north of Celje) and the coal-bearing beds between Zagorje and Trbovlje are described as Socka beds. Kuščer (1967), who studied the Tertiary area at Zagorje, used the name Socka beds dividing them into the lower and upper Socka beds. These beds are separated by the main coal seam. The lower Socka beds (footwall) are composed of clay, sand and locally gravel. The upper Socka beds are represented by marl, marly limestone and quartz shale. Upon the Socka beds lies conformably the bluish Marine marly clay with a rich microfauna. Recently, Jelen et al. (1992, 1994) established that the Socka beds from southern Karavanke are of Middle and Upper Eocene age. Since the beds with coal between Laško and Zagorje are of Oligocene age Jelen et al. (1992) as well as Odin et al. (1994) considered the up to that time Socka beds as Pseudosocka beds. 102_Karel Grad, Stevo Dozet, Rajko Petrica & Lija Rijavec Pseudosocka beds-Lower Egerian According to the data of the borehole Tdp-1/84 (Fig. 2) the oldest Tertiary rocks of the Trobni Dol area have a similar development as it can be seen between Zagorje and Laško where it is divided into the lower and upper Socka beds (Kuščer, 1967). In the eastern part of the Laško synclinorium there is few data about the Oligocene beds, owing to erosion of cover by younger sediments. The lower Pseudosocka beds in the borehole Tdp-1/84 consist of brownish and gray massive clay, inidvidual regular lenses of fine gravel (up to 1 cm thick) and of rare coal veinlets. The thickness of the lower Pseudosocka beds attains 14.85 metres. Approximately in the middle of the clay, which by analogy with the Laško syncli- norium can be nominated the footwall clay, about 5.50 m above the Triassic dolomite, occurs the first, about 30 cm thick coal seam that passes upwards into a 30 cm thick layer of clayey coal. The coal has the calorific value 20.36 MJ/kg (as received basis, a.r.b.), whereas the clayey coal reaches 4.29 MJ/kg (a.r.b.) only. In the borehole Tdp-1 the coal is overlain by an about 8.75 m thick grayish clay. Immediately above the footwall clay lies a 40 cm thick second coal seam. The core from the borehole was crushed, so it is possible that the coal is thicker. The calorific value of the coal is 15.94 MJ/kg (a.r.b.). According to the stratigraphie position this coal seam can be correlated with the coal seam exploited in the Laško synclinorium between Laško and Zagorje. The upper Pseudosocka beds start with a 26.85 m thick succession of the hanging wall marl. It consists of fine laminated grayish and yellowish marl, limy marl and marly limestone. In the upper part of the marl, approximately 3 metres under the boundary of the succession, a 30 cm thick coal seam of good quality occurs, resem- bling at first sight to anthracite. The calorific value of this coal is relatively high, 22.50 MJ/kg (a.r.b.). The hanging wall marl was formed in a shallow, calm and predominantly, brackish environment. It is laminated in the lower part, and it shows the signs of f]faser-bed- ding in the upper part. Above the hanging wall marl in the borehole Tdp-l/fe4 follows upwards a 42 m thick succession composed of rhythmic alternation of dark gray sandstone and siltstone characterised by organic admixture and bioturbation. This succession starts with a 2.15 m thick horizon of a black clay and claystone containing numerous small pelecypods with thin shells. Upwards lie conformably the following beds: - Black claystone. Thickness 2,1 metres. - Grayish, fine-grained sandstone alternating with siltstone. Thickness 1.6 metres. - Gray, fine to medium-grained, massive sandstone. Thickness 5.8 metres. - Dark gray flaser bedded siltstone. Thickness 0.40 metres. - Gray to yellowish gray sandstone with carbonate admixture, and white up to 2 cm thick calcite veins. Thickness 2.3 metres. - Dark gray, here and there flaser-bedded siltstone containing rare thin pelecypod shells. Thickness 3.4 metres. - Gray, massive, medium-grained, bioturbated carbonate sandstone. Thickness 3.4 metres. - Gray, massive, medium-grained bioturbated carbonate sandstone. Thickness 4.0 metres. - Thin-bedded, fine-grained, laminated sandstone and siltstone alternating with dark gray shale. Thickness 2.8 metres. Pseudosocka Beds with Coal in Borehole Tdp-1/84 Trobni Pol 103 Fig. 2. Geologic column of the Pseudosocka Beds with coal seams in the Tdp-1/84 borehole at Trobni Pol Sl. 2. Geološki stolpec psevdosoteških plasti s premogom v vrtini Tdp-1/84, Trobni Pol 104_Karel Grad, Stevo Dozet, Rajko Petrica & Lija Rijavec - Gray, massive sandstone. Thickness 3.6 metres. - Fossiliferous, bedded, yellowish gray marly limestone containing numerous pelecypods and gastropods. Thickness 1.6 metres. - Dark gray claystone alternating with a gray siltstone containing rare small pyrite grains. Thickness 1.7 metres. - Gray, massive sandstone passing gradually into a siltstone. Thickness 1.1 metres. - Coarse grained sandstone passing upwards into a siltstone. Thickness 4.2 metres. - Gray, clayey, here and there flaser-bedded siltstone. Thickness 2.3 metres. - Gray quartz sandstone with bioturbation. The grain thickness diminishes from bottom to top. The passage into the overlying Marine clay ("sivica" in Slovene) is gradual and fast. Thickness 4.7 metres. Coal Basic data on the Trobni Dol and Pojerje coal seams The abandoned Trobni Dol and Pojerje coal mines have been known for a long time. Their geology was already studied in the last century. The first data about the Trobni Dol area were presented by Z o 11 i k o f e r (1861), who studied the stratigraph- ie position of the productive formation. Granigg (1910) noted that in the Martin pit a lenslike, about 60 cm thick coal seam was mined. South of Martin pit there was another pit with a 70 cm thick coal seam containing a 37 cm thick sterile interlayer. In the hanging wall Petrascheck (1926/29) found a shale with Cyrena and a clay upon the shale. The exploited coal seam was 0.6-1 metres thick. He mentioned a shale with Cyrena in the hanging wall and a 40 cm thick bed of limnic limestone in the footwall. Under the limnic limestone he noticed an other 20 cm thick coal seam. According to the exploration borehole Tdp-1/84 data in the Trobni Dol area three thin coal seams occur in the Pseudosocka beds: The first coal seam is 30 cm thick. It lies in the footwall clay, 5.50 m above the Pre- Tertiary basement that is composed of the Triassic dolomite. The second coal seam with the thickness of 40 cm is situated at the contact between the footwall clay and the hanging wall marl. By its stratigraphie position this coal is correlative with the coal excavated in the coal mines of the Laško syncli- norium between Zagorje and Laško. We supposed that this coal was mined in the Trobni Dol area although, according to the Petrascheck's description (1926/29), it is not possible with certainty to conclude. The highest, 30 cm thick coal seam is situated in the uppermost part of the hang- ing wall marl and has the highest calorific value according to chemical analysis. The coal quality was estimated on the basis of the coal analyses from the borehole Tdp- 1/84 and from the surface. Owing to limited possibilities of sampling in the borehole the results of analyses have a limited value. Chemical composition of the Trobni Dol coal seams The results of the proximate and ultimate analyses of the coal from the borehole Tdp-1/84 and from the surface in the Trobni Dol area have been obtained. On the Pseudosocka Beds with Coal in Borehole Tdp-1/84 Trobni Pol 105 surface the Pseudosocka beds were only partly exposed, therefore the connections of individual samples with coal horizons are not certain. The coal sample No 47 has been collected east of the road Aškerc-Trobni Dol. The 20 cm thick coal outcrop is situated under the beds of the upper Socka limy marl. The results of the proximate and ultimate coal analyses from the surface are the following (table 1). Table 1. The chemical composition of the coal sample No 47 Tabela 1. Kemična sestava vzorca premoga št. 47 106 Karel Grad, Stevo Dozet, Rajko Petrica & Lija Rijavec The results of the coal analyses of the samples from the borehole Tdp-1/84 on the "as received basis" are the following (table 2). Table 2. The chemical analysis of the coal samples from the borehole Tdp-1/84 Tabela 2. Kemična analiza vzorcev premoga iz vrtine Tdp-1/84 Sample 1 - the coal within the footwall clay; depth 377.80-378.10 metres Sample 2 - the coal between the footwall clay and the hanging wall marl; depth 368.30- 368.70 metres Sample 3 - the coal from the upper part of the hanging wall marl; depth 343.40-343.70 metres Hamrla (1987) examined the mean random huminite-vitrinite reflectance of the coal from the borehole Tdp-1/84 at the depth of 368 m. This coal horizon is situated along the contact between the footwall clay and the hanging wall marl. By its strati- graphic position and maturation it is comparable with the coal seam in the Laško synclinorium. It is known that the maturation of the organic substance in a sediment is reflected in change of chemical and physical parameters. The attained stadium of transformation is named the stage of maturation or rank. The Trobni Dol coal was characterized byHamrla(1987)asa brilliant brown coal ("Glanzbraunkohle") with the following values of the coal rank parameters: mean random vitrinite reflectance 0.60 %, carbon content 69 % (dry ash-free basis; d.a.f.), volatile matter 47.8 % (d.a.f.) and the total moisture content 25 %. The maximal depth of burial was estimated to 800 metres. The rank of the Trobni Dol coal is relatively high with respect to the coals Pseudosocka Beds with Coal in Borehole Tdp-1/84 Trobni Pol__109 westward of the studied area. In Laško the coal rank amounts to 0.32 % and in Zagorje and Trbovlje 0.30 %. H a m r 1 a (1987) explained the anomalous rank of coal from the Trobni Dol area with possible thermal influence of andesite-dacite volcan- ism in the coal hanging wall. Petrascheck (1926/29) concluded that the higher maturity of the coal is caused by influences of marine environment after the forma- tion of peat. Fossils and age of coal-bearing beds The age of coal was defined on the basis of macro and microfauna. Stur (1871a,b) studied the rich macrofauna from the hanging wall beds and established their brackish character on the basis of certain marine species. In the yellowish white limestone from the Trobni Dol area he determined the following fossils: Natica helicina Brocchi Tympanotonus margaritaceum var. marginatum Grateloup Pirenella plicata var papillata Sandberger Pirenella plicata var. pustulata Al. Brogniart Cerithium rahtii Al. Brogniart Littorinella acuta Al. Brogniart Melania cf. falcicostata Hofmann Cytherea incrassata var., styriaca Rolle Cyrena semistriata Deshayes In the dark gray sandy shale, which is most probably equivalent of the silty and sandy succession above the hanging wall marl, S tur (1871) mentioned the following fossils: Brotia escheri Brogniart Brotia sotzkanensis Stur Unio eibiswaldensis Stur Chara sp. Stur (1871a,b) considered that the sediments from the Trobni Dol are the brack- ish and partly marine equivalent of the lacustrine "Socka" beds of Trbovlje. He cor- related the brackish "Socka" beds with the Upper Oligocene beds and Cyrena marl in Siebenbürgen and Upper Bavaria. Granigg (1910) ranged the Trobni Dol coal beds into the Lower Miocene Govce beds. Petrascheck (1926/29) also mentioned the lacustrine limestone from the footwall of the main coal seam. According to the borehole Tdp-1/84 data the hanging wall limestone and marl are developed only in the footwall of the third coal seam. From the hanging wall marl, which is usually 60 cm thick, Petrascheck (1926/29) quoted beside above-enumerated also some other fossils, namely: Congeria basteroti Deshayes Cardium thunense (?) Mayer Cerithium galeotti Nyst Neritina pietà Ferrusac 108_Karel Grad, Stevo Dozet, Rajko Petrica & Lija Rijavec Beside brackish forms Stur (187la,b) found in the waste material a dark gray sandy coal shale containing lacustrine fossils. The author could not define the posi- tion of these beds considering them brackish and marine. Munda (1939) tried repeatedly to determine the macrofauna of the coal-bearing succession, but the gath- ered material from the dump was not good enough to get new data and to permit con- clusions. He considered the "Socka" beds to be of the Chattian age. On the basis of determined microfossils Rijavec (1983, 1984a,c) concluded on the Oligocene age of the Trobni Dol coal horizons. At the depth 309.00 m to 326.00 m the washouts from the borehole Tdp-1/84 contain rare foraminifera Cydamina sp., Quinqueloculina sp., Ostracoda as well as imprints and calcitic cores of gastropod tests. In this interval, at the depth to 313.10 m to 315.10 m, an interlayer of marly limestone in the sandy and silty succession was found. It is interesting that in the marly limestone, the richest fossiliferous layer in the whole borehole Tdp-1/84, numerous undeterminable gastropods and pelecypods have been found. We do not know with certainty whether Stur, Petrascheck, Munda and others found the macro- fauna in a bed corresponding to this horizon, but it is very probable. In the borehole we found another horizon with less macrofauna in the immediate hanging wall marl at the basis of the sandy-silty succession. Jelen (1984) examined 15 samples from the borehole Tdp-1/84 and examined 30 thin sections of the Pseudosocka beds and Oligocene Marine clay. In positive samples the palynological contents was poorly preserved. In the clayey coal at the depth 376.80 m Jelen (1984) determined the following palynologie species: Spores: Verrucatosporites favus favus Thomson & Pflug Verrucatosporites sp. Laevigatosporites sp. Pollen: Monocolpopollenites tranquillus tranquillus Thomson & Pflug Inaperturopollenites hiatus Thomson & Pflug In the sample of silt at the depth 312.80 m Jelen (1984) determined the following palynological contents: Spores: Verrucatosporites favus favus Thomson & Pflug Polypodiaceoisporites sp. Pollen: Inaperturopullenites hiatus Thomson & Pflug Engelhardtioidites microcoryphaues verus Thomson & Pflug Monocolpopollonites sp. Jelen concluded that in the lower part of the borehole Tdp-1/84 as well as in the "Socka" beds of the Zagorje coal basin undistinct similarities of the palynological spectrum can be shown. Similarités are also observed in the upper "Socka" beds of both areas. Grayish Green Marine Marly Clay and Tuff - Lower Egerian At the depth of 299.50 metres in the borehole Tdp-1/84 (Fig. 3) rests without dis- cordance upon a sandstone the grayish green Marine marly clay. In the clay a foraminiferal fauna appears already 50 cm above the underlaying sandstone. The Pseudosocka Beds with Coal in Borehole Tdp-1/84 Trobni Pol 109 Fig. 3. Geologic column of the Upper Oligocene Marine marly clay and dacito-andesitic tuff from the borehole Tdp-1/84 at Trobni Pol Mi - Micropaleontologic analysis; PI - Palynologie analysis; + Positive; - Sterile Sl. 3. Geološki stolpec zgornjeoligocenske morske lapornate gline (sivice) in dacitnoandezitnega tufa V vrtini Tdp-1/84 Mi - Mikropaleontološka analiza; PI -Palinološka analiza; + Vsebuje mikrofavno; - Sterilna 110_Karel Grad, Stevo Dozet, Rajko Petrica & Lija Rijavec microfauna occurs upwards in numerous samples of the clay up to 159.40 metres. At that point begins a sedimentary succession composed of alternating dacite-andesitic fine-grained tuff, lapilli tuff and pyroclastic breccia. This succession goes on contin- ually upwards as far as to the point of 28.50 metres where the grayish green Marine marly clay reappears, alternating with tuffs to up to 12.50 metres, the base of the overlying alluvial deposits. In the grayish Marine marly clay above the tuffs Rijavec (1984a,c) found similar microfauna as under the tuffs. On the basis of microfauna from the interval 16.7m to 27m Rijavec ascertained the probable Lower Egerian age of the beds. Beside numerous foraminifera Almaena osnabrugensis also foraminifer Anomaloides granosus is present. In numerous samples of the Marine marly clay between 158.30 m and 299 m Rijavec (1984a,c) determined the following Upper Oligocene (Egerian) foraminifera: Glomospira charoides (Parker & Jones), Cyclammi- na acutidorsata (Hantken), Spiroplectammina carinata (d'Orbigny), Martinottiella communis (d'Orbigny), Cyclogyra polygyra (Reuss), Nodosaria longiscata d'Orbigny, Vaginulinopsis gladius (Phillippi), Vaginulinopsis pseudodecorata Hagn, Glandulina laevigata d'Orbigny, Sphaeroidina bulloides d'Orbigny, Stainforthia schreibersiana (Czjzek), Uvigerina cf. farinosa Hantken, Siphonina reticulata (Czjzek), Cibicides lobatulus (Walker & Jacob) Pullenia bulloides (d'Orbigny), Gyroidina soldanii d'Or- bigny, Anomalina affinis (Hantken), Cibicidoides ungerianus (d'Orbigny) Hanzawaia boueana (d'Orbigny), Melonis soldanii (d'Orbigny), Almaena osnabrugensis (Roemer), Hoeglundina elegans (d'Orbigny), Bathysiphon filiformis Sars, Haplophragmoides sp., Textularia sp., Gaudryina sp., Karreriella sp., Nodosaria sp., Lenticulina sp., Guttulina sp., Uvigerina sp., Chilostomella sp., Gyroidina sp., Heterolepa sp., Melonis sp., Miliolidae. In the Marine marly clay above the dacite-andesitic pyroclastic succession at the depth from 28.50 m to 12.50 m Rijavec (1984 a, c) determined the following foraminifera: Glomospira charoides (Parker & Jones), Martinottiella communis (d'Orbigny), Glandulina laevigata d'Orbigny, Sphaeroidina bulloides d'Orbigny, Uvigerina hantkeni Cushman & Edwards, Pullenia bulloides (d'Orbigny), Gyroidina soldanii d'Orbigny, Anomalina affinis (Hantken), Anomalinoides granosus (Hantken), Cibicidoides ungerianus (d'Orbigny), Heterolepa dutemplei (d'Orbigny), Melonis sol- danii (d'Orbigny), Almaena osnabrugensis (Roemer), Globigerina div. sp., Textularia sp., Cyclogyra sp., Lenticulina sp., Guttulina sp., Uvigerina sp., Heterolepa sp., Mili- olidae. Beside foraminifera in the Marine marly clay fish teeth, echinoid spines as well as limonitized and pyritized gastropod cores also occur For the Lower Egerian age are still characteristic numerous Paleogene foraminifera Vaginulinopsis pseudodecorata, Vaginulinopsis gladius and Uvigerina hantkeni. In the Lower Egerian beds estward and westward of Trobni Dol beside the above enumerated foraminifera also species Tritaxia (Clavulinoides) szaboi and Plan- ularia kubinyii are found. The grayish Marine marly clay is the most characteristic and regional wide-extended Oligocene sediment in the Laško synclinorium. Gorenjs- ka and the Savinja valley area. If andesitic tuffs occur, they usually lie in the hanging wall of the Marine marly clay. However, the Marine marly clay resembles very much to the Kiscell clay in Hungary. Opinions about the more precise age of the Marine marly clay and underlying Pseudosocka beds are still very different. A group of researchers (Kuščer, 1967; Buser, 1977, 1979; Cimerman, 1979; Pavšič, 1985; Jelen et al., 1990) attributed them the Middle Oligocene (Rupelian). Pavšič proved the age by means of nanoplankton. Jelen's statements about the Middle Oligocene Pseudosocka Beds with Coal in Borehole Tdp-1/84 Trobni Pol_113 repose on palynological research. On the basis of several ten years of investigations of foraminifera in Slovenia Rijavec (1984a, b, c) and Rijavec &Plenicar (1979), arrived at a decision that the Marine marly clay is of Egerian age. In favour of this age also speak the results of investigations of miogypsinas and lepidocyclinas at Zagorje (Papp, 1954). Lately, the results of absolute age datation on the basis of plagioclase from the volcanoclastic layers within the coal seam at Zagorje caused a great sensation (Odin et al., 1994). The analytical results indicate that the plagioclase samples were erupted at 25.0 ± 1.0 Ma (2 o), therefore the volcanoclastic layers (Pseudosocka beds) contain- ing the plagioclase were deposited during the Late Chattian. The precise age corre- sponds to the Lower Egerian, accurately to Late Chattian. The grayish green Marine marly clay lies directly upon the Pseudosocka beds with coal: according to this their Lower Egerian age is confirmed. Regarding numerous unsolved questions it will be necessary to continue systematic research of individual Oligocene basins in Slovenia. This research is also interesting and important for adjacent regions i.e. for the whole sedimentary area of the former Paratethys. Indications exist that from Hungary across Slovenia to Italy there was a relatively uniform sedimentary basin. Oligo-Miocene and Miocene beds Over the andesitic tuff lie the beds which were deposited between the Upper Oligocene and the Lower Miocene, and which can not be subdivided either by fauna or lithologically. Accordingly, the grayish green to brownish sandy clay as well as the beds of sandy clay sandstone and sand are ranged into the Upper Egerian (Petrica et al., 1995). According to lithologie and paleontologie characteristics the sandy- clayey beds, which in other parts of the Laško synclinorium overlie the Marine marly clay, correspond to the lower Govce beds. In the Trobni Dol area the upper Govce beds (Eggenburgian), Laško beds (Badenian) and incomplete Sarmatian beds are developed, too. The enumerated beds area already described in detail (see: Dozet & Rijavec, 1994;Petrica et al., 1995). Structural relations The investigated area is a part of the eastern continuation of the Tertiary belt which appears at Moravče and passes through Zagorje, Trbovlje, Hrastnik, Laško and east of Savinja. The entire Tertiary belt belongs to the Sava folds tectonic unit. Kuščer (1967) denominated the belt as Laško synclinorium, whereas other authors use the name Laško syncline. The Tertiary beds of the investigated area were subjected to two types of deforma- tions: 1) The deformations originated during the Tertiary sedimentation, manifested as erosional and tectonical-erosional discordances between the Pseudosocka beds and Pre-Tertiary basement, the Lower Miocene and Badenian (Tortonian) beds as well as the Badenian and Sarmatian ones. 2) The deformations occurred after the deposition of the Sarmatian beds. They were caused by orogenic activity which folded the Tertiary beds of the whole area. Kuščer (1967) found that the main orogenic phase in the Sava folds, which caused 112_Karel Grad, Stevo Dozet, Rajko Petrica & Lija Rijavec the folding of the Tertiary beds and influenced the origin of structures, v^^as the Attic orogenic phase that was active in the Lower Pliocene. Forces which caused the folding were acting from the north to the south. To the second type of tectonic deformations two sjoiclines (Laško, Planina) and the anticline Rudnica between them are ranged. During and after the folding came to a faulting and deformation of the folded structures. Fault systems with directions NW-SE, SW-NE, N-S and W-E originated. The strongest fault systems were those with the NW-SE and W-E direction. In the Laško syncline the synform was preserved undisturbed. Deformations arose at the northern flank where along the W-E fault at Podgorje one part of this limb sank, so that in the northern flank area the andesitic tuff came in tectonic contact with the Pre-Tertiary rocks. However, in the northern flank a normal succession of beds with- out any essential changes is observed. The synclinal core is built of Laško marl strata. The southern limb of the Laško syncline is also deformed. The preserved part of northern syncline and the core are somewhat sunk along the W-E fault regarding the southern limb which in the central part of investigated area strongly turned to the NE. Between Res j e and Matizel the southern limb of the syncline is divided in some smaller local synforms and antiforms. Only in the western part of the investigated area the southern limb preserved his shape. The limb was deformed along NW-SE, W-E and N-S faults. In the southern limb of the Laško syncline the upper Pseudosoc- ka beds. Oligocene Marine clay, Govce beds and Laško beds are developed. The crest of the Rudnica anticline is deformed similarly as the southern limb of the Laško syncline. It turns to the NE and becomes divided between Matizel and Resje in several smaller folds, synforms and antiforms respectively. Because of pre- dominantly clayey sediments and consequently a small density of measured dips it is not possible to define everywhere the crest of the anticline. The anticlinal crest pass- es through the grayish green marly clay in the western part of the investigated area, and east of the road Mala Breza-Trobni Dol it is totaly invisible. The southern Planina syncline is also strongly deformed, especially its southern limb which is overthrusted by the beds of the Pre-Tertiary basement. In the northern limb there are the same sediments as in the Laško syncline, with distinction that the Upper Oligocene sandy beds and Pseudosocka beds do not outcrop there. In the east- ern part of the mapped area the northern limb continues up to Matizel. The sandy clayey Egerian beds outcrop there, whereas in the western part of the mapped area the grayish green Egerian clay is to be found. Upwards in the northern limb the nor- mal Tertiary succession follows. In the synclinal core there are Sarmatian sandy marly clays and Sarmatian conglomerate, belonging according Winkler (1924) to the Carynthic Delta. The anticlinal axis has a direction SE-NE. The southern limb between Globoko and Mirni Dol is strongly tectonically deformed. In this area the Pre-Tertiary basement lies over the southern limb of the Planina syncline. For that reason the Sarmatian and Egerian beds are in inverse position. Consequently, between Mirni Dol and Globoko the Planina syncline passes to a plunging fold. Inside of the plunging southern limb of the syncline it also came to thrusting of Ter- tiary beds (Sarmatian and Egerian beds). In the eastern part of the area between Pojerje and Blatni Vrh it came to folding and smaller overthrusting. Also in the southern part of the Planina syncline the development of beds is normal from the Upper Oligocene to the Middle Sarmatian, but they are owing to strong tectonic deformations very thinned. In the mapped area the most expressive fault system has the NW-SE direction. Pseudosocka Beds with Coal in Borehole Tdp-1/84 Trobni Pol_115 Faults of this system transverse the whole area. It came to horizontal movements along the faults. Along the faults N-S and W-E especially the latter, occurred larger and stronger vertical movements of the studied area. For example, at Podgorje the northern limb of the syncline sank along the W-E fault. On the other hand, the faults in SW-NE direction did not essentially influence the geological structure of the mapped area. Suggestion for further investigations The most perspective area for investigation with exploration boring, regarding the results of detailed geological mappings and the boreholes, is the southern limb area of the Laško syncline. Especially perspective is the southern limb, from the road Trobni dol-Breze towards the west in the continuation of the Trobni Dol Oto coal field. In this part of the limb an about 30 cm thick coal seam outcrops. The coal lies between clastic and marly sediments corresponding to the Pseudosocka beds. The western part of the southern limb is not deformed so much that it would come to folding within the southern limb; in such a manner this part of fold preserved its shape. The beds in the southern limb area dip 25° to 35° towards NW. Regarding all these conditions we believe that this area is favourable for further investigation with exploration drilling. The northern limb of the Laško syncline at Podgorje, can also be prospective for further coal investigation with drilling since these beds are not tectonically deformed except along the contact with the Pre-Tertiary basement. If taking into account the thickness of individual litostratigraphic members found out by detailed geological mapping we expect there a coal seam at the depth about 300-350 metres. Less prospective is the area of the Planina syncline and eastern part of the southern limb of the Laško sjmcline. In this part of the investigated area, in Egerian outcrops and along the contact with the Pre-Tertiary basement, there are no Pseudosocka or ana- loguous beds, because towards the north they wedged out. Over the Pre-Tertiary basement lie sandy-clayey beds containing coal lenses. In the beds of gray to white sand and sandstone at Laška Vas we found several about 10-20 cm thick outcrops of coal. This syncline is also strongly tectonically affected. Its southern part is over- turned so that the Pre-Tertiary rocks are overthrusted upon the Tertiary ones. In the Planina syncline area of some interest is the Pojerje locality where before the Second World War an up to 4 metres thick coal seam was excavated. For this area it would be necessary to find out whether the coal seam appears also in the north- eastern continuation of the abandoned Pojerje coal-mine; therefore, the area is prospective for investigation with drilling. The eastern part of the southern limb of the Laško syncline is divided along the faults into several smaller folds with steep limbs. At present stage of investigations of the terrain this part is not suitable for exploration by drilling. Summary In the Trobni Dol area lie discordantly over the Pre-Tertiary basement Oligocene Pseudosocka beds intercalated with thinner seams of brown coal. They are compara- ble with the productive Pseudosocka beds in the wider Laško synclinorium area 114_Karel Grad, Stevo Dozet, Rajko Petrica & Lija Rijavec towards the west, between Laško and Zagorje, where economically more important coal field and coal mines are situated. In the Trobni Dol area, 8 km east of Laško, the brown coal was excavated in the past, and carried away by narrow-gauged railway. The beds with coal at Trobni Dol are exposed in a deformed anticline. The anticline is better expressed in the Rudnica area where in the anticlinal core prevalently the Triassic rocks came to light. At the depth of 385.00 m in the structural borehole Trobni Dol Tdp-1/84 lies discordantly upon the Triassic dolomite a 14.85 m thick footwall clay. Upon the footwall clay rests conformably a 40 cm thick brown coal seam which is by its stratigraphie position comparable with the productive coal seam in the area between Laško and Zagorje. Upon the coal lies a 26.85 m thick succession of fine stratified marly limestone. It is called the hanging wall marl, and this is also a very typical horizon in the area between Laško and Zagorje. Continuously over the marly limestone lies the 42 m thick succession of rhythmic alternating siltstone and sandstone which end the sedimentation of the Pseudosocka beds. At the depth of 299.50 metres starts without any visible discordance about a 140 m thick succession of bluish gray Marine marly clay known by the name "Sivica" and mostly containing rich microfauna which indicate the lower part of Egerian. Upwards, upon the Marine clay, at the depth 159.40 m, starts a cca 131 m thick pyro- clastic succession. Above the Marine clay, from the depth 28.50 m, alternate a pelitic tuff and Marine marly clay with the Lower Egerian microfauna. The Marine clay is the typical Oligocene sediment in the wider area of central and eastern Slovenia. By its lithologie development it is comparable with the Kiscell clay from Hungary. Pyro- clastic rocks are products of high silica dacite magma belonging to ignimbrites. Their characteristics indicate submarine pyroclastic streams. Pyroclastic rocks in the Trob- ni Dol area are the extreme westerly exposed larger outcrops of volcanic rocks in the Laško synclinorium. East of Trobni Dol we found them at Žusem in the Rudnica area. Towards the west the volcanic rocks occur in the form of thinner interbeds in the coal and Marine marly clay. Discussion and Conclusions The Pseudosocka beds at Trobni Dol show certain litostratigraphic differences in the upper part regarding their development towards the west. Namely, the Pseu- dosocka beds between Laško and Zagorje end with the hanging wall marl. At Zagorje Kuščer (1967) mentioned a special development of the upper Pseudosocka beds that are composed of grayish brown shale which often contains leaf imprints. There are several interlayers of sand within the shale succession resembling the Govce sand. East of the Kotredež brook there are clastic quartz sediments within the shale. Kuščer (1967) considered them the hanging wall. The Oligocene Marine clay with foraminifera at Potoška vas near Zagorje lies concordantly upon the shale. A similar stratigraphie position can be seen in the Trobni Dol borehole where the Marine clay lies concordantly upon the quartz sandstone and siltstone. It is necessary to emphasize that the alternation of sandstone and siltstone above the hanging wall marl in the borehole Tdp-1/84 does not represent any lateral equivalent in the area of the Laško synclinorium. The Pseudosocka beds of the area studied are divisible into the lower Pseudosocka beds, the main coal horizon, and the upper Pseudosocka beds. In the borehole Tdp-1/84 three coal seams occur. On the other hand, in the mapped Pseudosocka Beds with Coal in Borehole Tdp-1/84 Trobni Pol_117 area some other very thin (up to 1 cm) coal seams are to be found in the uppermost part of the Pseudosocka succession. Determined macro- and microfauna indicates that the Trobni Dol coal is of the Upper Oligocene age. The characteristics of the footwall, main coal horizon and hanging wall sediments indicate the following chronology of the geologic events: 1. Supply of continental waters which filled the depression with clay and sandy material, and deposition of the footwall clay. 2. Periodical ingressions of the sea caused mixing of the marine, brackish and limnic sedimentation and fauna. 3. The gathered fauna indicates predominantly brackish and limnic character of the coal-bearing beds. Limnic are probably the lower Pseudosocka beds under the main coal horizon. 4. The hanging wall marl is mostly a brackish sediment formed in a shallow lagoon. After the formation of the hanging wall marl oving to the intensive shallowing of the sea repeated filling up with sandy material occurred. 5. After the deposition of the hanging wall marls it came in the lagoon to a stronger continental water supply which filled up the lagoon with sandy mate- rial. In a brackish environment a vegatation reappeared, what is proved by lenselike coal seams and charred plant remains in the Upper Pseudosocka beds. 6. The sinking of the investigated area was intensified and the lagoon was flood- ed with the sea water; in a new somewhat deeper environment the marine Upper Oligocene grayish green limy clay was deposited what is proved by a rich foraminiferal fauna. Acknowledgements We are greatly indebted to Prof. Dr Vasja Mikuž for revision of macrofauna from the Pseudosocka beds according to data of Stur, Petrascheck and Munda. For techni- cal assistence in drafting and typing we would like to thank Ms. Metka Karer and Ms. Marjeta Oman. 116_Karel Grad, Stevo Dozet, Rajko Petrica & Lija Rijavec Psevdosoteške plasti s premogom v vrtini Tdp-1/84 Trobni Dol (vzhodne Posavske gube) Cilj članka je podrobneje prikazati zaporedje in razvoj oligocenske skladovnice Trobnega Dola in ga primerjati z razvojem zahodneje v Laškem sinklinoriju. V okviru raziskav premoga na območju Trobnega Dola vzhodno od Laškega sta bili poleg geo- loškega kartiranja površine na območju premogovnika Trobni Dol izvrtani razisko- valni vrtini Tdp-1/84 globine 385 m in Tdp-2/84 globine 400 m. Za preučevanje litostratigrafskih razmer je pomembnejša vrtina Tdp-1/84, ker je prevrtala normalno zaporedje oligocenskih plasti in dosegla predterciarno podlago. Vrtina Tdp-2/84 zaradi tektonskih razmer ni dosegla produktivnih plasti s premogom. Na sl. 2 in sl. 3 je prikazan razvoj oligocenskih plasti Trobnega Dola, ki jih po mikropaleontoloških raziskavah foraminifer prištevamo k zgornjemu oligocenu oz. spodnjemu egeriju. Psevdosoteške plasti so limnično-brakične. Pričenjajo se s talno glino in z vložkom premoga. Na talni glini je v vrtini 40 cm debela plast svetlega rjavega premoga. V krovnini premoga je 27 m debela skladovnica drobnoplastovitega krovnega lapornega apnenca. Krovni lapor je prekrit z 42 m debelim sedimentnim zaporedjem, ki ga sestavlja ritmično menjavanje peščenjaka in meljevca. Te plasti prehajajo brez diskordance v 140 m debelo lapornato glino, bogato s foraminiferami, ki kažejo na spodnji egerij. Ta glina je zelo razširjena v osrednji Sloveniji, podobna pa je Kiscelski glini na Madžarskem. V normalnem zaporedju leži na laporasti glini 131 m debela piroklastična skladovnica, ki je produkt visoko silicijske dacitne magme. Piroklastiti prehajajo navzgor v laporasto glino s podobno foraminiferno mikrofavno, kakršna je v njihovi talnini. Večino litostratigrafskih členov iz Trobnega Dola moremo primerjati z razmerami zahodneje v Laškem sinklinoriju, kjer je razvit premogov sloj, ki ga odkopavajo v več premogovnikih. Spodnji produktivni del v Trobnem Dolu prištevamo k Psevdosoteš- kim plastem. Te so bile doslej obravnavane kot Soteške plasti. Omenili smo že, da se psevdosoteška skladovnica Trobnega Dola pričenja s talno glino, ki vsebuje tanke vložke drobnega proda in 30 cm debel vložek premoga in da talni glini sledi v vrtini 40 cm debela plast rjavega premoga. Slednjega primerjamo po legi in glede na značaj talnine in krovnine s produktivnim premogovim slojem med Laškim in Zagorjem. Premog pripada svetlemu rjavemu premogu in ima odsevnost 0,60 % Ro, ki je najvišja med oligocenskimi vrstami premoga Laškega sinklinorija. Visoko odsevnost premoga je mogoče razložiti s termičnim vplivom vulkanizma pri Trobnem Dolu. S korelacijo litostratigrafskih členov smo ugotovili, da v krovnini laporja ležeča 42 m debela skladovnica Trobnega Dola, ki jo sestavlja ritmično menjavanje pešče- njaka in meljevca, ni značilna za Psevdosoteške plasti proti zahodu. Piroklastiti so v Laškem sinklinoriju razkriti v večjem obsegu le na območju Rud- nice; zahodno od Trobnega Dola pa se v lapornati glini pojavljajo samo tanjši vložki tufov in tufitov. Pseudosocka Beds with Coal in Borehole Tdp-1/84 Trobni Pol_117 References Bittner, A. 1884: Pie Tertiär-Ablagerungen von Trifail und Sagor - Jb. Geol. R.-A., 34, 433-600, Wien. Buser, S. 1977: Osnovna geološka karta SFRJ, list Celje 1:100 000. - Zvezni geološki zavod, Beograd. Buser, S. 1979: Tolmač lista Celje. Osnovna geološka karta SFRJ 1:100 000. - Zvezni geološki zavod, 72pp., Beograd. 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GEOLOGIJA 39, 119-131 (1996), Ljubljana Ambrus Beds - Important Key for Interpretation of Neocomian Paleogeography, Sea-Level Changes, Depositional Setting and Tectonics in Suha Krajina Area (Slovenia) Ambruške plasti in njihov pomen za interpretacijo neokomskih paleogeografskih, evstatičnih in tektonskih razmer na območju Suhe krajine (Slovenija) Stevo Dozet Geološki zavod Ljubljana Inštitut za geologijo, geotehniko in geofiziko Dimičeva 14, 1000 Ljubljana, Slovenija Key-words: carbonate sediments, lithology, genesis, paleogeography, Lower Cretaceous, Outer Dinarides, Central Slovenia Ključne besede: karbonatni sedimenti, litologija, geneza, paleogeografija, spodnja kreda. Zunanji Dinaridi, osrednja Slovenija Abstract The lower part of the Lower Cretaceous stratigraphie sequence at Ambrus, composed of limestones, dolomitic limestones, dolomites, intertidal breccias and overlying heterogeneous carbonate breccias is described in this paper. On the basis of stratigraphie order, fossil contents as well as the well-determined fossiliferous underlying Upper Malm and overlying Barremian carbonate sediments, the for- mation denominated the Ambrus beds was ascribed to the Neocomian. Fenestral limestones, laminated limestones and dolomites containing stromatolites, mud- cracks and numerous erosion and oxidation surfaces are interpreted as tidal storm deposits. The shallow water sediments, the breccias and the subaerial exposures, evidenced by relatively common karstification phenomena, are considered to be connected with eustatic sea-level variations and epeirogenetic movements. The lithology and areal distribution of these deposits indicate a sedimentation in a rel- atively symmetric, rather shallow lagoon. The breccias composed of various poorly sorted angular and subangular limestone and dolomite fragments, as well as of calcitic and dolomitic cement, have been attributed to tidal and cliff breccias. The majority of the breccia fragments indicate a pretty shallow water and subaerial sedimentation conditions. Kratka vsebina Najnižji del spodnjekrednega sedimentnega zaporedja pri Ambrusu sestavljajo apnenci, dolomitizirani apnenci, dolomiti in heterogene karbonatne breče. Glede na statigrafsko lego, fosile in s fosili dobro dokazane spodaj ležeče zgornje- malmske plasti ter zgoraj ležeče barremijske sedimente, smo formacijo, ki smo jo poimenovali Ambruške plasti, uvrstili v Neokom. Fenestralni in laminirani apnen- 120 Stevo Dozet ci in dolomiti s stromatoliti, izsušitvenimi porami ter številnimi erozijskimi in oksidacijskimi površinami so nastali v plimskem območju. Nastanek plitvovodnih karbonatnih sedimentov, breč in nadplimskih tvorb s številnimi pojavi zakraso- vanja povezujemo z evstatičnimi in epirogenetskimi premikanji. Litološka sestava in razširjenost teh sedimentov na površini kažeta na sedimentacijo v plitvi laguni. Breče, ki so sestavljene iz različnih slabo sortiranih oglatih do slabo zaobljenih apnenčevih in dolomitnih drobcev, vezanih s kalcitnim in dolomitnim cementom, smo uvrstili med plimske breče in breče strmih obrežij (cliff). Drobci kamnin v brečah kažejo na plitvovodne in nadplimske pogoje sedimentacije. Introduction The purpose of this preliminary work is to describe the carbonate formation, denominated the Ambrus beds that builds up the small hills Kamni vrh. Stražarjev vrh and Mali vrh at Ambrus. The most part of the data from the study area were obtained by detailed geological mapping for the Geological map of Slovenia on the scale of 1:50.000. This study is based on field mapping data and thin-section analysis. Fades characteristics of the Ambrus sedimentation have been considered, with the Fig. 1. Location sketch map of investigated area Sl. 1. Položajna karta raziskanega ozemlja Ambrus Beds - Important Key for Interpretation of Neocomian .■._121 purpose to explain the geological events of the Suha Krajina area (Fig. 1). In order to ascertain the geologic significance of the discontinuous breccia body, we have attempted to date the breccia exposures along the road that leads to Kamni vrh, and to reconstruct its shape, size, composition, depositional conditions and environment. In addition to this, we wanted to find out, whether the brecciation phenomenon was related to tectonic activity. The study of the Ambrus formation has a great impor- tance not only for the stratigraphy of the study area, but also for better explanation of the Lower Cretaceous paleogeography. On the other hand, the breccias provide an important key to the depositional setting during the Neocomian. An attention is given to the Ambrus breccia constituents, differentiating fragment and cement types, as well as to the underlying and overlying sedimentary successions, providing in this way a more general information on the brecciation process and evolution. As a mat- ter of fact, the carbonate breccias reflect a specific and relatively longstanding phase in the geologic history of the considered area. The carbonate rocks are classified using Folk's (1959) practical pétrographie classification of limestones and Dunham's (1962) classification of carbonate rocks according to depositional textures. The present work has been performed with sup- port of the IGGG-Geological survey of Ljubljana. Previous Work Šribar (1966) described the Jurassic sedimentary rocks between Zagradec and Randol in the Suha Krajina area. On the basis of microfossils and the stratigraphie position she divided the Jurassic stratigraphie sequence into the Lower and Middle Liassic, the Upper Liassic-Dogger, the Lower Malm and the Upper Malm. After styd- ing all the aspects of the occurrences of abberant tintinnids she found (1979) that abberant tintinnids from the Dinarides of the South Slovenia do not indicate the Valanginian stage. She attributed the transitional beds between Jurassic and the Lower Cretaceous to Berriasian. Buser (1979) mapped the Ribnica Map sheet area and divided the Upper Malm carbonate rocks of the area into the lower (Oxfordian and Lower Kimmeridgian) and upper part (Upper Kimmeridgian and Tithonian). The author subdivided the Lower Cretaceous beds into the following units: Valanginian, Hauterivian+Barremian, Apt- ian+Albian+ +Cenomanian. According to Buser (1989) the Outer Dinarides underwent a differentiation due to the formation of the Slovene trench, and the originally uniform area was dissected into two minor platforms, the Julian and the Dinaric one. Savie and Dozet (1985) described the general geology of the Delnice Map sheet area dividing the Lower Cretaceous succession as follows: Berriasian, Valanginian, Hauterivian, Barremian, Lower Aptian, Upper Aptian, Lower Albian and Upper Albian. To the Neocomian they attributed the limestone-dolomite-chert breccia. Dozet (1990) subdivided the Jurassic stratigraphie sequence of the Kočevje and Gorski Kotar area into 5 cenozones and 3 subzones by algae, foraminifera and pelecypods. Furthermore, 5 cenozones and 3 subzones are recognized in the Lower Cretaceous sequence by algae and foraminifera. Strohmenger and Dozet (1991) studied the stratigraphy, facies developments and geochemistry of the Jurassic carbonate rocks in Suha Krajina. The field studies showed that at least the uppermost part of Dogger was not deposited. 122_Stevo Dozet Stratigraphie Position The Neocomian Ambrus beds can be followed in a some kilometres wide area north of Ambrus. The treated beds are about 250 metres thick. They lie between the Upper Malm and the Upper Barremian beds. The underlying strata The strata occurring immediately bellow the Ambrus beds are composed of micritic, biomicritic, biointrasparitic, oncolitic and stromatolitic limestones, as well as early and late diagenetic dolomites and carbonate breccias that reflect the shallow subtidal, intertidal and supratidal cycles. The carbonate rocks enumerated above are more or less recrystallized and dolomitized. According to the texture they mostly belong to calcirudites and calcarenites. The Malm beds of the Suha Krajina area con- tain coated grains of algal origin that were formed in periodically and intermediately agitated water in a shallow subtidal environment. Some data suggest that a part of oncolites were deposited in a water of greater turbulence (Dozet, 1995b). The Upper Malm succession is composed predominantly of Clypeina and Tintinnina limestones and dolomites intercalated with carbonate breccias. Sedimentological features with- in the majority of limestones and dolomites point at shallow-subtidal, intertidal and supratidal depositional settings. The carbonate breccias prevalently occur in the uppermost part of the Malm stratigraphie sequence. Occurring in numerous stratigraphie levels of the Malm sedimentary succession at Korinj, the breccias have been named the Korinj breccias (Dozet&Strohmenger, 1996). Five genetically different breccias have been distinguished. The polymict karst breccia is interpreted to be the lateral equivalent of the Lower Malm/Upper Malm bauxite horizon (Strohmenger, 1988). Emplacement of carbonate breccia into the Malm sedimentary succession is a characteristic feature in certain places of the Outer Dinarides region, the Logatec plateau and especially in the Suha Krajina area (Dozet, 1995a). Mudstone breccia-conglomerate originated by desiccation. Textural and structural characteristics of some breccias indicate their intertidal and supratidal formation (tidal breccias). Dolomitic, limestone-dolomitic and limestone talus brec- cias were formed by accumulation and consolidation of talus at the base of coastal cliffs. Some talus breccias have been formed in relation to submarine synsedimentary faulting. The uppermost part of the Malm sedimentation is characterized by rhythmic sedi- mentation of light gray, micritic and laminated limestones and dolomites. The strati- graphic sequence described above belongs biostratigraphically to the Upper Malm Clypeina jurassica cenozone (Dozet, 1994, 1996). The overlying strata The strata which overlie the Ambrus breccias and which consist of platy and stratified (5 - 45 cm) limestones, dolomitic limestones and dolomites, sporadically intercalated with thin layers of small-scale intraformational carbonate breccias, belong to the Barremian. The limestones include fine, medium and thick-bedded, gray, dark gray and black, more or less bituminous micrites, pelmicrites, bioin- Ambrus Beds - Important Key for Interpretation of Neocomian .■._ 125 trasparites, biosparites and stromatolites. Among biomicrites and biosparites pre- dominate the foraminiferal and algal ones. The main constituents of the foraminifer- al limestones are benthic foraminifera, miliolids and algae Dasycladaceae. Rhythmic sedimentation of limestones can be often seen in this interval of the Lower Creta- ceous stratigraphie sequence. Rhythms of pelsparite-stromatolite are very common and typical. Also characteristic is a rhythmic alternation of early diagenetic and late diagenetic dolomites. From the biostratigraphical point of view the described succes- sion of limestones and dolomites belongs to the Salpingoporella muehlhergii (Lorenz) cenozone (Šribar, 1979). The gradational contact of the breccia and overlying strata is characterized by a development of alternations of up to 0.35 metres thick, light- brown coloured dolomites and equally thick, dark gray mudstones, locally with bird'S-eyes. The dolomite beds decrease in thickness from bottom to top. In fact, these dolomite beds are chiefly composed of coarse-grained structureless and finer-grained stromatolitic dolomites. The stromatolites within breccia testify to high-intertidal and supratidal conditions. Above this alternating succession the unit is mainly com- posed of mudstones. On the basis of field and sediment-petrographical data the over- lying carbonate strata (Barremian) are interpreted to be chiefly originated in a shal- low lagoon. The Ambrus Beds Berriasian The lower part of the Ambrus sedimentary succession consists of limestones, dolomitic limestones, dolomites, dedolomites and tidal carbonate breccias. Lime- stones are commonly more or less early and late-diagenetically dolomitized. Conse- quently, all transitional types between limestone and dolomite can be observed in the Ambrus stratigraphie sequence. Limestones were formed in shallow marine environ- ments, namely: lagoon, subtidal, intertidal and back reef. According to the structure and the texture the limestones belong to micrites, dismicrites, as well as stromatolitic and intraelastic limestones. Most typical and important are Favreina and Salpingo- porella limestones. The limestones are commonly more or less karstified and contain at some places residual materials. Erosive, rarely stylolitic contacts and surfaces can be found, too. Further on, the lower part of the Ambrus stratigraphie sequence which chronostratigraphically belongs to Berriasian consists of alternating late diagenetic, early diagenetic, structureless and stromatolitic-dolomites, as well as dedolomites. Early diagenetic dolomite is light gray to white, stratified (30-80 cm), fine-grained, cryptocrystalline to microcrystalline, laminated and stromatolitic, containing ostra- cods, rare gastropods, oncoids, shrinkage pores, fecal pellets and bird's-eyes. Late diagenetic dolomite is chiefly dark gray to brownish gray, coarse-grained (saccha- roidal), internally structureless, occurring in lenticular or irregular bodies. Small- scale brecciation and the limestone breccia become apparent at the Lower Malm/Lower Cretaceous contact and within the beds at the base. According to its origin it belongs to the tidal type of breccias. The strata occurring immediately bel- low the breccias reflect shallow intertidal and supratidal cycles. Tidal breccias, origi- nated due to desiccation, are overlain by fenestral and laminated limestones of pre- dominantly algal origin, and karstified limestones with residual materials. Stroma- tolitic dolomites, locally characterized by gastropod remains, are sometimes interca- lated within structureless dolomites. At the top of the described sedimentary succès- 124_Stevo Dozet Sion white and dark gray mudstones occur An increase in bed thickness towards the upper contact is present. The mudstones above the Lower Berriasian stratigraphie sequence represent a short transgressive trend. At the top of the transgressive strata mudstones with bird-s-eyes and stromatolites occur Neocomian (Valanginian to Lower Barremian) Ambrus Breccias General description of breccias The Neocomian heterogeneous carbonate breccias come to light in the Kamni vrh- Stražarjev vrh-Mali vrh area at Ambrus. They build the upper part of the Ambrus beds with an average thickness of 150 metres. The Ambrus breccias (Fig. 2) are prevalently massive. In the lower part of the breccias an unclear stratification can be seen. Better stratified are breccias from the upper part of the Neocomian lithologie column. The size of limestone and dolomite fragments varies considerably. In the lower part of the breccia unit the fragments are on an average 3 cm to 6 cm and in the upper one from 0.5 cm to 3.5 cm in size. The fragments are bound together by calcific and dolomitic cement and some clayey matrix. Since some carbonate fragments con- tain the Malm microfossils and due to the Barremian dasycladaceans in the overlying strata, the breccias chronostratigraphically correspond to Neocomian. In spots in the upper part of the breccia column a thick-bedded, white biomicrite and biopelmicrite with algae Clypeina? solkani occur, which confirms the Neocomian age of the brec- cias. According to the composition and sedimentological properties of the breccias we can conclude that after the Upper Malm important paleogeographic and depositional changes took place. These changes are supposed to be a consequence of epeirogenetic, eustatic and tectonic movements which caused the differentiation of up to this time relatively uniform environment. These movements caused faulting, uplifting, vertical displacements, local dry land and, accordingly, new paleogeographic disposition between the land and the sea. On the basis of morphological characteristics, the size, the shape, the poor sorting of breccia constituents, and with regard to the type of cement, we come to conclusion that during the deposition of the breccias there were great differences with respect to the base level of erosion. The section Brezovšče-Kamni vrh at Ambrus was investigated in the field, howev- er, the description of the breccias given here is based on numerous outcrops in the entire study area. About 30 thin sections from the type locality section and 20 thin sections from other outcrops were studied under the pétrographie microscope. The maximum thickness of the breccias at the type locality on Kamni vrh at Ambrus is 150 m, but elsewhere it can be extremely reduced. The contact with the underlying Berriasian rocks is pretty sharp and it is about parallel to bedding. The contact of the breccias with the overlying Barremian limestones and dolomites is in some places sharp, but locally a gradual transition of the breccias into the overlying carbonate succession can be seen. The dark gray to black heterogeneous carbonate breccias consist of fragments varying in dimensions from pieces of almost half a metre in length to the smallest ones of microscopic dimensions. On the basis of the fragment size the breccias can be divided in two parts: the coarse-grained (5-55 cm) lower part and the finer-grained (0.5-3.0 cm) upper one. The Ambrus breccias are mostly mas- sive carbonate sediments. However, the upper part of the breccia complex is often more or less clearly stratified. Moreover, carefull examination of the fragment Ambrus Beds - Important Key for Interpretation of Neocomian .■. 125 Fig. 2. Geologic column of the Ambrus beds in the Suha Krajina area 1 Bedded limestone; 2 Bedded coarse-grained dolomite; 3 Stromatolitic dolomite; 4 Massive breccia; 5 Bedded breccia; 6 Clypeina jurassica Favre; 7 Aberrant tintinnids; 8 Gastropods; 9 Favreinas; 10 Algae (generally); 11 Clypeina Ž solkani Conrad & Radoičić; 12 Dasycladaceae; 13 Benthic foraminifers; 14 Stromatolites SI. 2. Geološki stolpec Ambruških plasti na območju Suhe krajine 1 Plastnati apnenec; 2 Plastnati debelozrnati dolomit; 3 Stromatolitni dolomit; 4 Masivna breča; 5 Plastnata breča; 6 Clypeina jurassica Favre; 7 Velike tintinine; 8 Polži; 9 Favreine; 10 Alge (splošno); 11 Clypeina ? solkani Conrad & Radoičić; 12 Dazikladaceje; 13 Bentonske fora- minifere; 14 Stromatoliti 126_Stevo Dozet lithology show that many of the larger displaced fragments still maintain a relative orientation approximately parallel to the stratification giving the breccias of the lower part an apparent stratification, too. On the other hand lenses of very light gray to white, thick-bedded Clypeina? solkani limestone can be observed in the upper part of the Lower Cretaceous brecciated lithologie interval. Petrography of the breccia fragments The Ambrus breccias are composed of limestone, dolomite and silica fragments. The fragments are rather variable from millimetre to half a metre-sized. Larger frag- ments occur more frequently in the lower part of the breccia. Angular and subangu- lar fragments are the main constituents of the breccias. Some fragments, especially from the lower part of the breccia interval, contain calcite and/or dolomite veins. Normally, the breccias have a heterogeneous and rather chaotic fabric. Namely, the breccia which is locally associated with tectonics, consists of a mixture of large and small blocks of irregular shape and different age and very fine-grained, tightly packed material accumulated in a state of total disorder It is oligomictic with dolomite fragments as the most abundant rock type. Limestones fragments are common in the upper part of the breccia complex. The predominant limestone type of fragments is white lime mudstone containing small algae and ostracods. Other mudstone fragments contain rare mollusc remains. The mudstones are interpreted as lower intertidal to shallow subtidal muds. The exis- tence of broken ostracods suggests that some of these bioclasts were redeposited. Algal laminated mudstone fragments, consisting mainly of dense accumulation of pellets, are also common. The algal laminated mudstone is interpreted as having been deposited in the intertidal zone or possibly in a shallow subtidal environment. Lime- stone fragments are usually subordinate constituents of the Ambrus breccias, but in spots they become even predominant. The limestone fragments of the Ambrus brec- cias belong to the following structural and textural types: black, greyish black, dark gray, dark brownish gray, brownish gray, gray, moderate gray, light gray and white micrites, biomicrites, biopelmicrites, biosparites, biointrasparites, intramicrites, intrasparites, intrasparrudites, as well as grained, stromatolitic, fenestral and dolomitic limestones. Dolomite fragments are predominant (60-85 %) particles in the Ambrus breccias. Three dolomite types are present in the fragments, namely: brownish gray, dark brownish gray and grayish black dolomicrite, dolosparite and stromatolitic dolomite. Gray dolomicrite was recognized in the lower breccia unit: The dark brown idiotopic dolosparite fragments predominate in the lower breccia unit. Dolomite in crystalline form almost always occurs together with calcitized and dolomitized mudstones or is interbedded with grainy limestones. It consists of subhedral to euhedral dolomite crystals. This dolomite rarely retains original sedimentary textures. In outcrop it is often intensively altered by surface weathering. Fragments composed solely of stro- matolitic dolomite also exist. These dolomites normally retain original sedimentary textures. Here and there gastropod sections, ostracod shells, as well as fecal pellets and algal skeletons can be observed in the stromatolitic dolomite. All three dolomite types constitute continuous beds in the lower part of the Ambrus beds, i.e. in the sed- imentary succession immediately underlying the cliff breccias, as well as the dolomites in the Upper Malm dolomite-limestone succession. Ambrus Beds - Important Key for Interpretation of Neocomian .■._ 127 Silica fragments occur only sporadically in the studied breccia. They are present exclusively in the middle part of the upper breccia unit and belong to chert. The sili- ca fragments are usually more than 5 centimetres in size. Breccia cement and matrix The cement in Ambrus breccias belongs to fine-grained calcite, dolomite, rarely matrix. In spots, coarser sparry crystals originated as a result of crystallization of fine-grained miciritic carbonate can be observed. Occasionally, only coarsely crystalline calcite (sparry calcite) cement fills the space among fragments. Since the matrix itself is often brecciated, it clearly postdates the lithification of the microsparitic matrix. As already said, the two breccia units were differentiated on the basis of the grain size and the material filling the interstices among grains. In the lower breccia unit the sparry calcite cement is preceded by a finelly crystalline cal- cite. Moreover, the clayey fine-grained interstitial material contains individual clasts and dolomite crystals. The dolomite crystals commonly are abraded and/or broken, being in any case formed before brecciation. Some smaller mudstone fragments, incorporated in the mud, are completely recrystallized. Larger cavities may be partly sediment-filled or in part spar-filled which created geopetal fabrics. In fact, the sedi- ment forms the floor, and the sparry calcite the upper part of the cavity. Genesis The Ambrus beds represent an important key to the depositional setting during Neocomian time intervals as well as to major tectonic events in the Suha Krajina area. The occurrence of stromatolites, mud-cracks, erosion surfaces, karstification phenom- ena, accumulations of insoluble residue, breccias, rhythmical alternations of highly dolomitized and laminated lime mud in the lower part of the Ambrus beds, lead us to conclusion that the finely stratified dolomites are supratidal deposits. The lack of fos- sils as well as the structural characteristics suggest current-agitated conditions. Fur- thermore, fine stratification of the intertidal and supratidal mud deposits is per- formed by storms that transport and deposit marine sediment into the intertidal and supratidal setting. It should be noted that the fragmentation of the newly formed sed- iment occurred at shoaling and temporary withdrawal of water by dessication and mud-cracking. Irregular dried-out and mud-cracked polygons have been broken into angular fragments, being later deposited and lithified together with remained lime mud. The lithologie composition, the scarity of fauna as well as textural and structur- al characteristics of the breccias indicate their intertidal and supratidal formation. The main characteristics of the cliff breccias are angular to subangular carbonate clasts of uniform or polymict composition, a very dense packing of clasts, a very poor sorting without grading or bedding, and different-sized fragments. It should be emphasized that this all speaks in favour of hypothesis that the breccias were formed by accumulation and consolidation of rock fragments derived from cliffs i.e., a high, very steep to overhanging face of rocks rising above the shore, usually produced by physical disintegration, chemical decomposition, faulting and erosion. The talus has been chiefly formed by gravitational falling of loose fragments, and their accumula- tion and consolidation at the foot of the described escarpments or steep walls. 128_Stevo Dozet Fossils and Age The lov^^er part of the Ambrus beds contains numerous Favreina salevensis Paréjas which are almost always rock-forming, further on Salpingoporella annulata Carozzi, Thaumatoporella parvovesiculifera (Raineri), Verneuilinidae and Textulariidae. Fos- sils have not been found in the matrix of the breccias so far Consequently, we can describe biofacies and define the age of the Ambrus breccias on the basis of the fossil association from the rock fragments. The biofacies can be referred to the Clypeinal solkani Conrad & Radoičić zone, which is typical for the carbonate platform shallow marine environment of the Neocomian age. Considering the constituent breccia frag- ments, their fossil contents, the stratigraphie position as well as the underlying and overlying fossiliferous carbonate sediments the breccias are of Valanginian, Hauteri- vian and very probably of the Lower Barremian age. During the Neocomian the restricted lagoon was developed in the study area. Detrital influx within the area studied was insignificant, suggesting that the sur- rounding dry land was built of carbonate rocks. The lithologie composition, structur- al and textural characteristics of the sediments suggest that these sediments were formed in a shallow-marine setting. The stratification of breccias is poor, what is comprehensible, since strata in these depositional conditions could not be formed. Paleogeographic Interpretation According to the composition and sedimentological properties of the breccias, we can conclude that after the deposition of the Upper Malm beds important paleogeo- graphic and depositional changes took place. The quoted changes, which are sup- posed to be the consequence of epeirogenetic, eustatic and tectonic movements, caused the differentiation of up to this time relatively uniform environment. These movements and forces caused faulting, uplifting, vertical displacements, local dry land and, accordingly, new paleogeographic disposition of the land and the sea. On the Jurassic/Lower Cretaceous boundary some parts of the Suha Krajina area were subjected to tectonic movements as a consequence of the Late Kimmerian oro- genetic phase (Dozet, 1989), resulting in an uplifting and rupturing of individual parts of the bottom of the sea. The new formed land gave the material for origin of the heterogeneous limestone-dolomite sedimentary breccias. A new paleogeographic picture between the land an the sea developed. The Neocomian carbonate breccias that originated predominantly in shore regions are genetically closely related to the mentioned paleogeographic changes. On the basis of morphological characteristics, the size, the shape, the poor sorting of breccia constituents, and with regard to the type of cement, we come to conclusion that during the deposition of the breccias, there were great differences with reference to base level of erosion. The coast region was characterized by steep, often vertical and even overhanging cliffs and with a strong water dynamics, but the transport was very short. With regard to the composition of the coarse-grained carbonate rocks it is evident that then being land, as source area of rock material, was composed exclu- sively of carbonate rocks. At new conditions of sedimentation carbonate breccias were formed. Ambrus Beds - Important Key for Interpretation of Neocomian .■.__ 131 Depositional environment of the Berriasian beds (Lower Ambrus Beds) A poor faunal diversity i.e., a low number and a low quantity of species, as well as stromatolites, bird's-eyes, numerous local erosion surfaces, common occurrences of marine and meteoric cements, dolomitization, common occurrences of karstified car- bonate rocks, clearly indicates shallow subtidal to intertidal and even shortstanding periodical supratidal setting during Berriasian as well as Valanginian, Hauterivian and very probably the Lower Barremian. Deposition of the brecciated rocks (Ambrus breccias) The brecciated Neocomian carbonate succession at Ambrus was deposited in a very shallow restricted lagoonal setting. The predominance of the shallow intertidal to supratidal carbonate fragments i.e., dolomites, algal laminates and mudstones with bird'S-eyes within the breccia indicates an overall restricted shallow lagoonal setting. Bellow the breccia in the Ambrus-Kamni vrh type section the pétrographie evidence suggests that the restricted lagoon periodically changed into dry land. The first small brecciation could have resulted from small-scale periodic seasonal dessication under evaporative conditions. The lower breccia part underwent two major phases of forming. The first probably occurred soon after deposition during a short period of emergence. The existence of an emergence period between the lower and upper breccia part is resumed from the observation that the mud matrix is absent in the upper breccia part. The carbonate groundmass material may originate from unlithified mud, occurring at the top of the lower breccia unit, or may relate to mud infiltration at the initial stages of sedimentation of the upper breccia unit. After the emergence period sedimentation resumed with deposition of mudstones. The dolomite beds become less prevalent through time and finally disappeared. Characteristic appearances within the breccia such as veined fragments, re-brec- ciated breccia fragments and the presence of two groundmass generations (micro- crystalline and sparry calcite cement) exhibit at least two phases of formation of breccia. Initial formation of breccia occurred soon after deposition during a short period of emergence. During this stage the original carbonate beds locally became veined and fractured. Carbonate mud infiltrated into interstices between the frag- ments. Finally, the breccia fragments were cemented by sparry calcite. Conclusions During the Upper Triassic, Jurassic and Cretaceous periods the study area was a part of the Dinaric Carbonate Platform. As far as tectonics is concerned, in the Jurassic and the Lower Cretaceous periods the Dinaric Carbonate Platform was not subjected to any stronger tectonic move- ments (Savie, 1973; Bus er, 1979, 1980, 1989; Dozet, 1989, 1994). Consequently, in the Upper Malm and the Lower Cretaceous a relatively continuous sedimentation occurred, interrupted with periodical, short-lived local interruptions, as a conse- quence of intensified epeirogenetic movements of the Carbonate Platform. These movements caused periodical land forms especially at the time between the Lower and the Upper Malm as well as between the Upper Malm and Neocomian. 130_Stevo Dozet The Malm and the Berriasian sedimentation was, generally speaking, a result of three different modes of sediment forming: 1) - land setting, 2) - changeable shallow marine and subaerial setting and 3) - shallow marine setting. The beds between fossiliferous underlying Upper Malm Tintinnina and Clypeina limestones and overlying Barremian Dasycladacea limestones at Ambrus have been named the Ambrus beds. The lower part of the Ambrus beds, belonging to Berriasian, is interpreted as a shallow water deposition with considerable degree of subaerial exposures. The pre- dominance of laminites, mudstones with birdseyes and shallow intertidal to suprati- dal carbonate fragments indicates that the treated sequence was originally formed in a shallow restricted lagoonal setting. The upper part of the Ambrus beds is occupied by heterogeneous carbonate brec- cias. In the breccia interval the heterogeneous dolomite breccias are predominant, the limestone-dolomite breccias are less extended, whereas pure limestone breccias are rare. Chronostratigraphically, the Ambrus-breccias are of Valanginian, Hauterivian, and probably of the Lower Barremian age, since in their composition the fragments of dark gray to black carbonate fragments, being common in Barremian, are predom- inant. From the biostratigraphic point of view the Ambrus beds are included in the Clypeina? solkani Conrad & Radoičić zòne (Neocomian). It seams acceptable to conclude that the Neocomian heterogeneous breccias dis- cussed above, composed of the Upper Berriasian, Valanginian, Hauterivian and very probably the Lower Barremian fragments, could not be exposed by erosion alone. The reason can be found in tja« increasingly more intensive movements of the sedi- mentary basis from the Berriasian to the Upper Barremian. Interruption in the stratigraphie record without larger angular discordance testi- fies to the statement that from the Upper Malm, Berriasian respectively, to the Upper Barremain predominantly epeirogenetic movements with local disturbances existed, contributing to the origin of the Ambrus breccias. Finally, our main concept is, the heterogeneous Ambrus breccias with limestone and dolomite constituents are products of intensified epeirogenetic and tidal move- ments, eustatic sea-level changes, erosion as well as local synsedimentary tectonics. Ambrus Beds - Important Key for Interpretation of Neocomian .■.__ 131 References Buser, S. 1979: Tolmač za list Ribnica. Osnovna geološka karta SFRJ 1:100 000. Zvezni geološki zavod, 60 pp., Beograd. Buser, S. 1980: Stratigraphie gaps in Paleozoic and Mesozoic beds in Slovenia. - Symp. Geol. Reg. Paleont. - Inst. Geol. Reg. Paleont. Fak. Min. Geol. Univ Belgrade, 335-345, Beograd. Buser, S. 1989: Development of the Dinaric and Julian carbonate platforms and of the intermediate Slovenian basin (NW Yugoslavia). - Mem. Soc. Geol. It., 40 (1987), 313-320, Rome. Dozet, S. 1983: Tolmač lista Delnice. Osnovna geološka karta SFRJ 1:100 000. Type-writ- ing. - Geološki zavod Ljubljana, 109 pp., Ljubljana. Dozet, S. 1989: Tectonic movements in the Younger Paleozoic and Mesozoic in the Kočevje area, southern Slovenia (orig. Slov). - Rud.-met. zbornik, 36/4, 663-673, Ljubljana. 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GEOLOGIJA 39, 133-157 (1996), Ljubljana Dachstein Limestone from Krn in Julian Alps (Slovenia) Razvoj dachsteinskega apnenca na Krnu v Julijskih Alpah Bojan Ogorelec Geološki zavod Ljubljana Inštitut za geologijo, geotehniko in geofiziko Dimičeva 14, 1001 Ljubljana, Slovenija Stanko Buser Univerza v Ljubljani, Naravoslovnotehniška fakulteta Oddelek za geologijo, Aškerčeva 2, 1000 Ljubljana, Slovenija A stari moj Km, And my old Km ki seval okrog milijone je krat that shone many million times o soncu ko zlat, in sun like a golden coin, a V zimi neštetokrat bil je srebrn, while in winter he was silvery so many times. in vedno je gledal brezčutno k nam dol, and always he looked merciless down on us, sè srcem brez čuta je srečen, happy in his impassive heart, saj on je pač večen, eternal as he is. (Simon Gregorčič, Iz predsmrtnic, 9) (Simon Gregorčič, from Songs before death, 9 Slovenian poet (1844-1906), bom in the village Vrsno by Km) Key words: Dachstein limestone. Upper Triassic, sedimentology, paleogeo- graphy, Julian Alps Ključne besede: dachsteinski apnenec, zgornji trias, sedimentologija, paleogeo- grafija, Julijske Alpe Abstract The Dachstein limestone from Km is characterized by Lofer development. The section encompasses 30 cyclothems on average 3-4 metres thick. Intra- and supratidal environment of deposition is evident by stromatolites, loferite and tem- pestile breccias. They were all locally affected by early diagenetic dolomitization. Biomicritic limestone with several horizons of megalodont clams was deposited in shallow and restricted shelf. Basal members A of the Lofer cyclothem are devel- oped only exceptionally. Solution cavities are fairly common, being infilled by sparry calcite and insoluble rich red limestone. The limestone was deposited on the Julian carbonate platform near its passage part to the southerly lying Slovenian basin. In this part reigned specific circum- stances that resulted into formation of very numerous corrosion vugs; they are filled in their central parts by variegated marly clay. Interesting are frequent tem- 134 Bojan Ogorelec & Stanko Buser pestite layers. Their origin is explained by synsedimentary tectonic processes that caused fracturing and slumping in unconsolidated limestone beds. Kratka vsebina Dachsteinski apnenec na Krnu kaže vse značilnosti loferskega razvoja. S pro- filom je bilo zajetih 30 ciklotem, ki so v povprečju debele 3 do 4 metre. V med- in nadplimskem okolju so nastajale stromatolitne in loferitne plasti ter tempestitit ("nadplimski konglomerat"); vse je ponekod zajela zgodnjediagenetska dolomitiz- acija. V plitvem in mirnem šelfu se je odlagal biomikritni apnenec z več horizonti megalodontidnih školjk. Bazalni členi loferske cikloteme A so razviti le izjemoma. Pogoste so korozijske votline, zapolnjene s pasovitim sparitnim kalcitom in resid- ualno karbonatno glino. Apnenec je nastal na Julijski karbonatni platformi blizu pregibnega dela z juž- neje ležečim Slovenskim bazenom. V tem delu so bile specifične okoliščine, ki so povzročile nastanek izredno številnih korozijskih votlin; le-te v središčnem delu zapolnjuje različno obarvana laporna glina. Zanimive so pogostne plasti tempesti- tov. Njihov nastanek razlagava s sinsedimentarnimi tektonskimi procesi, ki so povzročili razlamljanje in zdrsnitve še nekonsolidiranih plasti apnenca. Introduction When approaching the middle Soča River area, the eye is caught by vast moun- tainous massifs of the Julian Alps among which is especially dominant the mighty summit of Krn (fig. 1). These massifs are prevailingly built of the more than 1000 meters thick sequence of light thick bedded limestone that is known in the geological literature as the Dachstein limestone. Fig. 1. Massive of Dachstein limestone with Krn in the foreground, taken from Kolovrat Sl. 1. Dachsteinski apnenec na Krnu, posnet s Kolovrata Dachstein Limestone from Krn in Julian Alps (Slovenia)__ 135 The Dachstein limestone, or the Dachstein Formation, is of Late Triassic Norian-Rhaetian age. The name is derived from the Dachstein massif near Salzburg. In the larger part of the Julian Alps the formation is developed mostly as thick-bed- ded limestone and dolomitized limestone (Selli, 1963; Kuščer et al., 1974; Bus er, 1986, 1987; Jurkovšek, 1987;) in places, the bedded limestone passes into more or less extensive reefs of coral limestone (Turnšek & Buser, 1991). Below the Norian-Rhaetian Dachstein limestone lies a thick succession of layered Main dolomite the lower part of which extends down into the Carnian stage. The develop- ment of the Main dolomite and Dachstein limestone in Julian Alps is equal, or very similar as in the wider region of the Northern and Southern Alps (Sander, 1936; Zankl, 1967, 1971; Flügel, 1963, 1972; Fischer, 1964, 1975; Bosellini, 1967; Bosellini & Rossi, 1974), Dinaric Mountains (Buser, 1974; Ogorelec, 1975, 1988; Ogorelec & Rothe, 1993; Dozet, 1990; Herak et al., 1967; Babić, 1968; Dimitrijevič & Dimitrij evie, 1988; Čadjenović, 1988), Hungary (Fülöp, 1976; Haas, 1994), and even Sicily (Ma t a velli et al., 1969; Catalano et al., 1974). This is an indication of unique depositional and paleogegraphic conditions in the wide region of the Northern and Southern Alps and the Mediterranean in Norian and Rhaetian times. Such circumstances were possible only through a sedimentation process of limestone that was equilibrated with sinking of the carbonate platform (Fischer, 1964; Bosellini, 1967). During the Middle Lias a general disintegration of the entire system of large car- bonate plates happened. Breaking and sinking of particular parts was accompanied locally by forming of more or less thick carbonate breccias and neptunian dikes (Bernouilli&Jenkyns, 1974). Such breccias do not occur in the southern slopes of Krn where the studied traverses is situated, but they are excellently exposed in immediate vicinity, on the Krnska škrbina and near the lake at Lužnica (Babić, 1980/81; Buser, 1986). The quiet depositional environment on the carbonate plat- form continued from Rhaetian to Lias, so that the formation of dislocation fissures in the Slovenian part of the Julian Alps, as well as the slope breccias and neptunian dikes took place in Jurassic only, more precisely in the Late Lias. Such cases were recorded also near Bovec and on Mangart (Jurkovšek et al., 1990). The traverse on Krn (figs. 2 and 3) covers only the smaller upper part, equal to about one tenth of the entire thickness of the Dachstein limestone. The goal of the presently described study was the recording of lithologie and microfacial character- istics of the limestone especially with the intention of comparison with the beds of the same age in the Southern and Northern Alps. The complex of the Dachstein lime- stone on Krn is thicker, attaining above 1000 meters; owing to the position of beds and monotonous development of the limestone the investigation was limited to the most diversely developed part of the formation which comprises 30 cyclothems. The beds underlying the Dachstein limestone on Krn are not exposed. The Lower Jurassic Lias shallow marine limestones that normally overlie the Late Triassic Dachstein limestone are preserved as erosion remnant on the Batognica Mountain, only a few hundred meters southeast of the Krn summit. So it may be concluded that the sampled Dachstein limestones on Krn belong to the upper part of Upper Triassic. The Lias beds have a larger extension in northern slopes of Polovnik northeast of Krn (Kuščer et al., 1974; Buser, 1987). The studied massif of the Dachstein limestone belongs in the tectonic sense to a large overthrust structure named after Krn the Krn nappe (Buser, 1986). As the marginal part of the Julian Alps the Krn nappe is thrust over the Rutar nappe (fig. 2) 136 Bojan Ogorelec & Stanko Buser Fig. 2. Structural map of the Km area and location of the investigated section Sl. 2. Tektonska karta ozemlja okrog Krna in položaj raziskanega profila that consists of Jurassic and Cretaceous sediments of the deeper marine development of the Slovenian basin (Buser, 1986, 1989). The limestone on Krn v^as researched in the frame of the studies for the Basic geo- logic map 1:100,000, sheet Tolmin and Videm, in 1979 (Buser, 1986, 1989). Description of the Traverse The Dachstein limestone was examined in a 160 meters thick continuous traverse that is situated on the south slopes of Krn next to the mountaineering trail between the Kožljak saddle and the Gomišček refuge below the Krn summit (fig. 2). The tra- verse comprises only the upper part of the several hundred meters thick succession with a rather monotonous development of beds. The same textural and lithologie rock types keep repeating up to the summit of Krn. The traverse is throughout its course excellently exposed so that also lateral passages and changes in the rock can be examined. In the southern slope of Krn the beds of Dachstein limestone dip gently towards northeast (55/25). They are to a large degree covered by slope talus and mountain grass, but they may be nevertheless observed in detail in roadcuts of the winding mil- itary road that dates from the First World War The characteristic roof-like south slope of Krn was most probably formed in a large rockslide of limestone beds during the Ice Age, and is not conditioned by the downslope directed dip of the limestone Dachstein Limestone from Krn in Julian Alps (Slovenia) 137 Fig. 3. Lithologie column of the Km section; Dachstein limestone SI. 3. Litološki stolpec profila Krn; dachsteinski apnenec 138_ Bojan Ogorelec & Stanko Buser beds, as it is the case for many slopes of the Soča valley. The limestone beds in this slope of roof-like shape dip into the slope. In the entire traverse alternate cyclically thicker beds of biomicritic limestone and thinner beds, characteristic for deposition in the inter- and supratidal environ- ments. They comprise chiefly the stromatolitic horizons, laminite, loferite and tem- pestites ("supratidal conglomerate"). Individual cyclothems are from one to five meters thick, 3-4 meters on the average, and exceptionally they attain also 15 meters (fig. 3). The lithology and sedimentology of the Krn limestone at Krn are similar to that of the Northern Alps (Sander, 1936; Fischer, 1964; Flügel, 1963, 1972; Zanki, 1967, 1971). Such development was named by Sander the Lofer fades after the Loferer Steinberge massif, and Fischer (1964) introduced for the cyclothemes the term "Lofer Cyclothem". Characteristic for a classic Lofer cyclothem (fig. 4) is alter- nation of three lithologie members - thinner beds of basal breccia with cement of red or green residual carbonate clay (the A member), stromatolitic or loferitic horizon (B member), and thick beds of biomicritic limestone (C member). The Dachstein lime- stone at Krn shows all characteristics of the Lofer fades, although its development is in a sense specific. On Krn irregularly alternate especially the B and C members, while the basal breccia appears only in two cyclothemes of the investigated traverse. These breccias suggest episodic and short lived interruptions of deposition, i.e. local emersions. The larger part of the beds in the investigated traverse belongs to the somewhat recrystallized limestone of light olive grey color It occurs in 30 cm to 2 m thick beds, and is typical for deposition in the subtidal environment. According to texture, the limestone is biomicritic and pelmicritic, and it contains usually 10 to 30 % allochems. Among the fossils individual foraminifers (Involutina sp.), skeletal algae (especially of genus Solenopora sp., Thaumatoporella parvovesiculifera Raineri), gastropods, ostracods, echinoderm plates and fragments of bivalve shells. The Norian-Rhaetian age of beds is proved by numerous, up to 20 cm large megalodontid shells that appear in several beds. Of the megalodontid shells most commonly both valves are pre- served. During the early diagenesis the originally probably aragonitic shells were washed out, and their moldic pores were filled by coarse grained fibrous calcite dis- playing zonal crystal growth. Seldom in parts of these valves also red carbonate clay can be observed. It represents the mechanic residual deposit as an internal sediment. Among the allochems are the most abundant the pellets with frequent up to 5 mm large micritic plasticlasts admixed to them. The micritic matrix is in places recrystal- lized to microsparite, while in certain samples it is partly leached out and replaced by fine grained sparite. The energy index of the sampled rocks is low to very low It indicates a quiet depositional environment that was only at times moderately agitated. Deposition in littoral environment is suggested primarily by laminite and stromatolitic horizons. The laminite layers are up to 80 cm thick, and individual laminae measure from a few mm to 1 cm, and contain numerous sheet and mud cracks. The mineralogy of laminite consists of a mixture of micritic calcite and dolomite. We presume the forming of dolomite during the time of early diagenesis owing to salty pore solutions saturated with ions. The brines were rising through capillary mechanisms in the uncon- solidated carbonate mud at times of exposure to the supratidal environment (the "capillary concentration" dolomitization model - Illing et al., 1965). Periodically occurred as a result of tectonic processes breaks and slumps of incompletely lithified Dachstein Limestone from Krn in Julian Alps (Slovenia) 139 Fig. 4. Different tjrpes of cyclothems in the Dachstein limestone from the Krn section. Classical Lofer cyclothem after Fischer (1964) is on the left 1 - Megalodontidae; 2 - Corals and oncoids; 3 - Limestone with shrinkage pores (loferite); 4 - Laminite; 5 - Stromatolite; 6 - Tempestile layers ("flat pebble conglomerate") with carbonate blocks; 7 - Solution cavity; 8 - Breccia with residual carbonate clay Lofer cyclothem: member A - Red or green residual sediment enriched by clay and iron miner- als; residue of weathered material; member B - Laminated and dolomitised stromatolite or loferite; intertidal environment of deposition; member C - Megalodon limestone; subtidal envi- ronment SI. 4. Različni tipi ciklotem, ki se javljajo v dachsteinskem apnencu na Krnu. Levo je klasična loferska ciklotema po Fischerju (1964) 1 - Megalodonti; 2 - Korale in onkoidi; 3 - Apnenec z izsušitvenimi porami (loferit); 4 - Laminit; 5 - Stromatolit; 6 - Tempestitne plasti ("nadplimski konglomerat") s karbonatnimi bloki; 7 - Korozijske votline; 8 - Breča z residualno karbonatno glino Loferska ciklotema: člen A - Rdeči ali zeleni residualni sediment, bogat z glino in železovimi minerali; preperinski material; člen B - Pasoviti, dolomitizirani stromatolit ali loferit; medplim- sko okolje sedimentacije; člen C - Megalodontidni apnenec; podplimsko okolje sedimentacije parts of the limy bottom. Up to 80 cm long and up to 10 cm thick carbonate slabs or scales were formed, and they give to the rock the appearance of "flat pebble con- glomerate", (fig. 5). These carbonate slabs are often turned up and curved at margins along the longitudinal axis. Fissures between slabs are filled by granular calcitic sparite. In literature such sediments are known as tempestites (Aigner, 1982). The origin and classification of sedimentary structures formed in the supratidal environ- ment owing to disiccation and breaking of incompletely lithified carbonate laminae and bands were described in Upper Triassic beds of the Dolomites byAssereto and Kendall (1977). They named such structures "tepee", the term for Indian tent of pyramidal shape. 140_ Bojan Ogorelec & Stanko Buser Fig. 5. Large carbonate blocks, mostly of loferitic and stromatolitic origin, composing tempestile SI. 5. Velike raztrgane karbonatne luske, po sestavi pretežno loferitne in stromatolitne, ki grade tempestit The stromatolitic horizons are up to 40 cm thick, and they are more frequent mostly in the middle part of the traverse. The larger part is a stromatolite of polygo- nal type (Ai t ken, 1967; Gebelein, 1969), with up to 2 mm thick parallel laminae. The horizons of spongy texture are very rare (pi. 3, fig. 1). The interspaces of stroma- tolitic laminae and tiny disiccation pores (fenestrae, shrinkage pores) are filled by transparent sparitic cement, and in certain larger pores also geopetal structures with internal micrite can be found (pi. 2, fig. 1). Stromatolitic horizons are prevailingly in part dolomitized. The proportion of dolomite which is microcrystalline and associat- ed with organic laminae is estimated at between 5 and 19 %. Forming of dolomite in stromatolitic layers is connected with early diagenetic processes in the supratidal environment with an intense activity of microorganisms. The cyanophytes that participating in formation of stromatolites caused with their decay an increase in COg" ions in the microenvironment which promoted the crystallization of dolomite (Gebelein & Hoffman, 1973). Owing to increased contents of organic matter in the sediment during growth of stromatolites these beds are of darker color than the country rock, and can be macroscopically distinguished in the field. A special lithology of rock characteristic for the supratidal environment is the micritic and pelmicritic limestone with disiccation marks (pi. 1, fig. 1-2, pi. 2, fig. 2-3). Layers of this limestone, called loferite after Fischer (1964), are quite fre- quent in the traverse, and are up to 50 cm thick. The mud cracks measure up to sever- al mm and are oriented with their longer axis parallel to bedding. The features are a consequence of drying and shrinkage of unconsolidated carbonate mud during the phases of the supratidal environment, and their share might attain 40 % of the rock. They are filled with coarse grained sparite, while in larger vugs also internal micritic sediment and gravitational (stalactitic) cement can be found (pi. 2, fig. 3). The latter Dachstein Limestone from Krn in Julian Alps (Slovenia)___141 is typical for diagenesis under meteoric conditions, an indication of episodic expo- sure of the limestone during sedimentation above the sea level. In the lower part of traverse in places thinner layers of oncoid limestone can be seen. The oncoids measure up to 3 cm and display typical concentric structure with numerous algal envelopes (pi. 3, fig. 2-3). They are slightly dolomitized, like the stro- matolitic laminae. Individual oncoids are often overgrown. The origin of oncoids is associated with a slightly more agitated environment, with tidal channels in which the tidal currents enabled steady movement and their concentric growth. In the entire traverse occur in several layers also solution cavities measuring sev- eral cm to a few dm. They are an indication of episodic emersions of Dachstein lime- stone, and they represent paleokarstic passages and caves. They are filled by several generations of variously colored sparitic calcite, so that they display a variegated cocade structure. Especially pretty and large solution cavities are developed on Krn summit where they are often filled also with red residual carbonate clay (fig. 6, pi. 2, fig. 4). The limestone with numerous variegated solution cavities is an interesting ornamental stone. Fig. 6. A detail of the solution cavity filled by sparry radial calcite and red carbonaceous clay; the top of Krn, natural size Sl. 6. Detajl korozijske votline, ki jo zapolnjujeta conami sparitni kalcit in rdeča karbonatna glina; vrh Krna, naravna velikost Paleogeographic Conditions during Forming of Dachstein Limestone The Upper Triassic rocks that build the predominant part of the geotectonic unit of the Southern Alps, to which also the Krn area with the studied traverse belongs, were deposited on the Julian carbonate platform that was formed at the beginning of the Late Triassic. South of this platform extended the deeper marine Slovenian basin that wedged out in the area of the present central Soča valley between Kobarid and 142_ Bojan Ogorelec & Stanko Buser Srpenica. Owing to wedging out of the Slovenian basin the Julian and the Dinaric carbonate platforms bordered westwards directly one to the other, and continued far- ther west to neighboring Italy as a unique Trento platform (Buser & Debeljak, 1996). The depositional circumstances on the Dinaric and Julian platforms were differ- ent during the Late Triassic, as indicated by the Main dolomite that contains only rare megalodontid bivalves on the Dinaric platform (Ogorelec & Rothe, 1993), while these are extraordinarily numerous in the C member on the northerly situated Julian platform. Characteristic for the Dachstein limestone in the described traverse on Krn is the outstanding appearance of large solution vugs and tempestites, or the "flat pebble conglomerate". This is typical in the Julian Alps also in the environs of Krn on Polovnik, in the Soča valley southeast of Bovec and in Bohinj along the road from the Voje valley to the Blato pasturage. Especially characteristic are cavities in which the walls are rimmed by calcite of zonal texture, while the centers are filled by red, yel- low to violet carbonate clay. In other areas the cavities are less frequent, and they are mostly filled by calcite only. An interesting fact is that solution cavities occur only in limestone layers that were deposited in the subtidal environment of the carbonate platform, and that they never reach into the stromatolitic and laminated layers. The extraordinary abundance of solution cavities indicates special condition dur- ing their genesis. The margin of the carbonate platform, on which the limestone of Krn was deposited, was the most exposed part to frequent uplifts of the sea bottom or to oscillations of the sea level, and with that to longer land phases. During these events occurred intense karstification and forming of insoluble argillaceous residue, or fossil soils, that were washed to central parts of solution cavities. There is the still open question on the absence of these cavities in the stromatolitic and laminated lay- ers. There they also could be logically expected, since during land phases also these beds were subjected to weathering. One of possible explanations might be also that the stromatolitic beds were more resistant against karstification than pure limestone owing to their high dolomite content. The beds of the Dachstein limestone in the examined traverse on Krn were deposited on the extreme southern shallow marine margin of the carbonate platform, and they border at present with the tectonic overthrust contact on the southerly lying deposits of the Slovenian basin. Along the thrust border probably only an insignifi- cant part of the Dachstein limestone beds were eroded, so that the southern part of the old carbonate platform remains more or less preserved. In the southern slope of Veliki Stador southeast of Krn are still preserved the Norian-Rhaetian reef limestones that represent the lateral equivalent of the bedded Dachstein limestone (Turnšek & Buser, 1991). These limestones are an additional indication of the extreme southern margin of the Julian carbonate platform on which in places just along its flexure the coral reefs thrived. The origin of tempestites in the area of the present Krn cannot be reliably explained by stormy events. Up to one meter long and several decimeters thick, half lithified limestone slabs could not have been formed by such events. Furthermore, on these slabs there are no traces of shorter or longer transport. The slabs are not limited by sharp cracks that could be formed at surface drying of limy mud. The joints between them are "welded", filled by calcitic sparite. The origin of tempestites is explained by the present authors by episodic earthquake events that caused cracking and slumping of still unconsolidated limy mud. The earthquakes were the most fre- Dachstein Limestone from Krn in Julian Alps (Slovenia)_ 145 quent and strong exactly along the border of the platform that sunk along steep faults into the southerly extending Slovenian basin. The extraordinary exposition of this part of the carbonate platform to tectonic effects is indicated in a later time (Late Lias) by deep, wide open tension fault cracks that were filled by breccias with red cement in the form of neptunian dikes. These very phenomena are spatiually associated with the wider area of Krn where numerous tempestite layers occur. Conclusion The lithology and microfacies of the Norian-Rhaetian Dachstein limestone at Krn suggest that the rock was deposited in a very shallow sea. The textural types of lime- stone indicate incessant altenation of supra- and subtidal depositional environment. For the supra- and intratidal environment are typical the stromatolitic beds, mud cracks, limestone with shrinkage pores (loferite) and flat pebble conglomerate. According to the Standard Microfacies classification (SMF) and the Fades Belt clas- sification (FB, Wilson, 1975; Flügel, 1978) the dolomitized stromatolitic and loferitic limestones of the intratidal environment may be attributed to 19 and 20 SMF and 8 to 9 FB (restricted platform and littoral evaporites). The majority of lime- stone was deposited in a very shallow water that was not deeper than 10 to 20 meters. The energy index of examined samples is low to very low which leads to the idea of quiet depositional conditions in the restricted part of the carbonate platform with local lagoons. The limestones of the subtidal environment show indications of standard microfacies (SMF) 8, 9, 13 and 18 (biomicrite, biosparite, oncoidal grain- stone, foraminiferal and algal limestone), and belong to the environment of open to partly restricted carbonate platform (FB 7 and 9). The enumerated characteristics and monotonous development of the Dachstein limestone in the extended region of the Alps, as well as its impressive thickness suggest a rather flat paleorelief. The car- bonate platform sank very slowly, and also the deposition was taking course in equi- librium with sinking. The limestone emerged locally many times, and was exposed to paleokarstification, as indicated by numerous solutioin cavities filled by sparitic cal- cite (sinter) and residual carbonate clay. A similar development of the Dachstein limestone with numerous cyclothems as that on Krn is known from a wider region of west Slovenia, especially in the Julian Alps, as for example in the Kanin mountains, Trenta (Jurkovšek et al., 1990), Pokljuka and Kobariški Stol (Bu s er, 1986, 1987), Polovnik (Kuščer et al., 1974), and from Trnovski gozd and margin of the Banjška planota (Ogorelec, 1975, 1988; Ogorelec & Rothe, 1993). Characteristic for the Dachstein limestone of the entire mentioned region are all the elements of the classic Lofer development for which is typical the predominance in these cyclothems of the B and C members, and extreme rarity of basal breccias with residual clay (A member). The very frequent solution cavities were formed in the uppermost southern part of the Dinaric Julian carbonate platform that was the most exposed to long lasting land phases, or at least more often than the northerly lying lagoonal region. Since these cavities appear only in limestone (C member) of the cyclothem, and not in the B lay- ers of cyclothem (stromatolitic layer), this might be the reason for less intense karsti- fication of early diagenetically dolomitized stromatolitic layers than the correspond- ing limestone layers. The origin of tempestites is associated with frequent earth- 144_ Bojan Ogorelec & Stanko Buser quakes that caused cracking and slumping in the still unconsolidated limestone beds. The most intense earthquakes occurred just at the edge of the Julian carbonate plat- form and the southerly lying Slovenian basin where the Dachstein limestone of the studied traverse was formed. Razvoj dachsteinskega apnenca na Krnu v Julijskih Alpah Uvod Ko se približamo srednjemu Posočju, se naš pogled ustavi na obsežnih gorskih masivih Julijskih Alp, med katerimi posebno izstopa mogočni vrh Krna (sl. 1). Te masive v večjem delu gradi prek 1000 metrov debela skladovnica svetlega in debelo- plastnatega apnenca, v geološki literaturi znanega kot dachsteinski apnenec. Dachsteinski apnenec oziroma dachsteinska formacija je zgornjetriasne, noriško- retijske starosti. Ime ima po masivu Dachstein pri Salzburgu. V večjem delu Julijskih Alp je razvit predvsem kot debeloplastnati apnenec in dolomitizirani apnenec (Selli, 1963; Buser, 1986, 1987; Jurkovšek, 1987; Kuščer et al., 1974); sem in tja pa plastnat apnenec prehaja v bolj ali manj obsežne grebene koralnega apnenca (Turn- šek & Buser, 1991). Pod norijsko-retijskim dachsteinskim apnencem leži debela skladovnica plastnatega glavnega dolomita, katerega nižji del sega še v karnijsko stopnjo. Razvoj glavnega dolomita in dachsteinskega apnenca je v Julijskih Alpah enak ali zelo podoben kakor na širšem prostoru Severnih in Južnih Alp (Sander, 1936; Zanki, 1967, 1971; Flüge 1, 1963, 1972; Fischer, 1964, 1975; Bosellini, 1967; Bosellini & Rossi, 1974), Dinarskega gorstva (Buser, 1974; Ogorelec, 1975, 1988; Ogorelec & Rothe, 1993; Dozet, 1990; Herak et al., 1967; Babic, 1968; Dimitrijevič & Dimitrijevič, 1988; Čadjenovič, 1988), Madžarske (Fülöp, 1976; Haas, 1994) in celo Sicilije (Matavelli et al., 1969; Catalano et al., 1974). To kaže na enotne sedimentad j ske in paleogeografske razmere na širšem prostoru Severnih in Južnih Alp ter delu Mediterana v noriju in retiju. To je bilo možno le z uravnoteženim procesom sedimentacije apnenca in tonjenja karbonatne platforme (Fischer, 1964; Bosellini, 1967). V srednjem liasu je prišlo do splošnega razkosanja celega sistema velikih karbon- atnih plošč. Lomljenje in tonjenje njenih posameznih delov je lokalno spremljalo nas- tajanje bolj ali manj debelih karbonatnih breč in neptunskih dajkov (Bernouilli& Jenkyns, 1974). Te breče na samem južnem pobočju Krna, kjer leži posneti profil, niso prisotne, so pa odlično odkrite v njegovi neposredni bližini, na Krnski škrbini in pri jezeru v Lužnici (Babić, 1980/81; Buser, 1986). Mirne sedimentacijske danosti na karbonatni platformi so se iz retija nadaljevale še v lias, tako da je prišlo do nas- tanka prelomnih razpok na slovenskem delu Julijskih Alp in pobočnih breč ter nep- tunskih dajkov šele v juri oziroma v zgornjem liasu. Taki primeri so tudi pri Bovcu in na Mangartu (Jurkovšek et al., 1990). S profilom na Krnu (sl. 2 in 3) smo zajeli le manjši vrhnji del, okrog desetino celotne formacije dachsteinskega apnenca. Namen te raziskave je namreč bil, da ugo- tovimo litološke in mikrofacialne značilnosti apnenca predvsem zaradi primerjave z enako starimi plastmi v Južnih in Severnih Alpah. Sam kompleks dachsteinskega apnenca na Krnu je sicer debelejši in doseže preko 1000 metrov, vendar smo se zaradi Razvoj dachsteinskega apnenca na Krnu v Julijskih Alpah__147 lege plasti in monotonega razvoja apnenca omejili le na najbolj pestro razviti del for- macije, s katerim smo zajeli 30 ciklotem. Talnina dachsteinskega apnenca na Krnu ni odkrita. Spodnjejurski liasni plitvo- morski apnenci, ki ležijo normalno nad zgornjetriasnim dachsteinskim apnencem, so ohranjeni kot erozijska krpa na hribu Batognica le nekaj sto metrov jugovzhodno od vrha Krna. Tako lahko sklepamo, da pripadajo vzorčevani dachsteinski apnenci na Krnu vrhnjemu delu zgornjega triasa. Večji obseg pa imajo liasne plasti na severnem pobočju Polovnika, severovzhodno od Krna (Kuščer et al., 1974; Bus er, 1987). Tektonsko pripada raziskani masiv dachsteinskega apnenca obsežnemu pokrovu, ki ima ime prav po Krnu - Krnski pokrov (Buser, 1986). Kot robni del Julijskih Alp je Krnski pokrov narinjen na Rutarski pokrov (sl. 2), katerega grade jurski in kredni sedimenti globljevodnega razvoja Slovenskega bazena (Buser, 1986, 1989). Apnenec na Krnu smo posneli v okviru raziskav za Osnovno geološko karto 1:100.000, list Tolmin in Videm, leta 1979 (Buser, 1986, 1987). Opis profila Dachsteinski apnenec smo raziskali v 160 metrov debelem sklenjenem profilu, ki poteka po južnem pobočju Krna ob planinski poti med prevalom Kožljak in Gomi- ščkovim zavetiščem pod vrhom Krna (sl. 2). Profil zajema le vrhnji del več sto metrov debele skladovnice s precej monotonim razvojem plasti. Isti strukturni in litološki tipi kamnine se ponavljajo vse do vrha Krna. Profil je vseskozi odlično odkrit, tako da opazujemo lepo tudi bočne prehode in spremembe v kamnimi. Plasti dachsteinskega apnenca vpadajo na južnem pobočju Krna pod blagim kotom proti severovzhodu (55/25). Večji del so pokrite s pobočnim gruščem in planin- sko travo, vendar jih je moči kljub temu lepo opazovati v vsekih vijugasto speljane vojaške poti iz prve svetovne vojne. Značilno strehasto oblikovano južno pobočje Krna je verjetno nastalo ob velikem podoru apnenčevih plasti v ledeni dobi in ni po- gojeno z vpadom apnenčevih plasti po pobočju navzdol, kot je to pri številnih poboč- jih v dolini Soče. Apnenčeve plasti na tem strehi podobnem pobočju vpadajo v samo pobočje. V celotnem profilu se ciklično menjavajo debelejše plasti biomikritnega apnenca in tanjše plasti, značilne za sedimentacijo v med - in nadplimskem okolju. To so predvsem stromatolitni horizonti, laminit, loferit in tempestiti ("nadplimski kon- glomerat"). Posamezne cikloteme so debele od enega do pet metrov, povprečno 3-4 metre, izjemoma pa dosežejo tudi do petnajst metrov (sl. 3). Litološko in sedimentološko je apnenec na Krnu razvit podobno kot v Severnih Alpah (Sander, 1936; Fischer, 1964; Flügel, 1963, 1972; Zanki, 1967, 1971). Tak razvoj je Sander imenoval po masivu Loferer-Steinberge loferski facies, Fischer (1964) pa je za cikloteme uvedel termin "loferska ciklotema". Za klasično lofersko ciklotemo (sl. 4) je značilno menjavanje treh litoloških členov - tanjših plasti bazalne breče z vezivom rdeče ali zelene residualne karbonatne gline (člen A), stromatolitne- ga ali loferitnega horizonta (člen B) in debelih plasti biomikritnega apnenca (člen C). Dachsteinski apnenec na Krnu kaže vse značilnosti loferskega faciesa, vendar je raz- vit nekoliko svojsko. Na Krnu se nepravilno menjavata predvsem člena B in C, med- tem ko se bazalna breča javlja le v dveh ciklotemah raziskanega profila. Te breče na- kazujejo občasne in kratkotrajne prekinitve v sedimentaciji oziroma lokalne okop- nitve. 146_ Bojan Ogorelec & Stanko Buser Večji del raziskanega profila oziroma plasti pripada nekoliko rekristaliziranemu apnencu svetlo olivno sive barve. Javlja se v 30 cm do 2 metra debelih plasteh in je značilen za sedimentacijo v podplimskem pasu (subtidal environment). Po strukturi je apnenec biomikriten in pelmikriten ter vsebuje navadno 10 do 30 % alokemov. Med fosili opazujemo posamezne foraminifere {Involutina sp.), skeletne alge (predvsem iz rodu Solenopora sp., Thaumatoporella parvovesiculifera Raineri) gastropode, ostra- kode, ploščice ehinodermov in odlomke školjčnih lupin. Norijsko-retijsko starost plasti dokazujejo številne, do 20 cm velike megalodontidne školjke, ki se javljajo v več plasteh. Megalodontidne školjke so največkrat ohranjene z obema lupinama. V času zgodnje diageneze so bile prvotno verjetno aragonitne lupine izlužene, njihove moldične pore pa je zapolnil debelozrnati vlaknati kalcit s conarno rastjo kristalov. Poredko opazujemo v delih teh lupin tudi rdečo karbonatno glino, ki predstavlja mehanski rezidualni nanos kot interni sediment. Med alokemi so najpogostnejši peleti, mednje pa so večkrat pomešani še do 5 mm veliki mikritni plastiklasti. Mikrit- na osnova je ponekod rekristalizirana v mikrosparit, v nekaterih vzorcih pa je tudi delno izprana in nadomeščena z drobnozrnatim sparitom. Energijski indeks vzorcev je nizek do zelo nizek. Kaže na mirno sedimentacijsko okolje, ki je bilo le občasno nekoliko razgibano. Sedimentacijo v litoralnem okolju nakazujejo predvsem laminit in stromatolitni horizonti. Plasti laminila so debele do 80 cm, posamezne lamine pa merijo od nekaj mm do 1 cm in vsebujejo številne izsušit- vene razpoke (sheet & mud cracks). Mineralna sestava laminila je mešanica mikrit- nega kalcita in dolomita. Predvidevamo, da je dolomit nastal v času zgodnje diagene- ze zaradi slanih pornih raztopin, nasičenih z Mg^"^ ioni, ki so se kapilarno dvigale v nekonsolidiranem karbonatnem blatu, v času, ko je bil ta izpostavljen nadplimskim razmeram ("capillary concentration" model dolomitizacije - Illing et al., 1965). Občasno je zaradi tektonskih procesov prišlo do lomljenja in zdrsa še nepopolnoma litificiranih delov apnenčevega dna. Nastale so do 80 cm dolge in okoli 10 cm debele karbonatne plošče oz. luske, ki dajejo nakopičene kamnini videz nadplimskega kon- glomerata ("flat pebble conglomerate", - sl. 5). Karbonatne plošče oziroma luske so ob robovih podolžne osi mnogokrat zavihane ali usločene. Razpoke med ploščami zapolnjuje zrnati kalcitni sparit. V literaturi so taki sedimenti znani kot tempestiti (Aigner, 1982). Nastanek in klasifikacijo sedimentnih tekstur, ki so nastale v nad- plimskem okolju zaradi izsuševanja in lomljenja še nepopolnoma litificiranih kar- bonatnih lamin in pasov, sta iz zgornjetriasnih plasti Dolomitov opisala Assereto in Kendall (1977). Take teksture sta poimenovala "tepee" (originalni izraz za piramidasto obliko indijanskega šotora). Stromatolitni horizonti so debeli do 40 cm in so pogostejši predvsem v srednjem delu profila. Večji del je stromatolit poligonalnega tipa (Altken, 1967; Gebelein, 1969), z do 2 mm širokimi in vzporednimi laminami. Horizonti s spužvasto strukturo so zelo redki (tab. 3, sl. 1). Medprostore stromatolitnih lamin in drobne izsušitvene pore (fenestrae, shrinkage pores) zapolnjuje prozorni sparitni cement, v nekaterih večjih porah pa opazujemo tudi geopetalne teksture z internim mikritom (tab. 2, sl. 1). Stromatolitni horizonti so povečini nekoliko dolomitizirani. Delež dolomita, ki je mikrokristalen in vezan na organske lamine, cenimo med 5 in 10 %. Nastanek dolo- mita v stromatolitnih plasteh povezujemo z zgodnjediagenetskimi procesi v nad- plimskem okolju ob intenzivni udeležbi mikroorganizmov. Cianobakterije, ki so udeležene pri nastanku stromatolitov, povzročajo namreč pri svojem razpadanju po- višanje CO3" ionov v mikrookolju, kar pospešuje kristalizacijo dolomita (Gebelein & Hoffman, 1973). Zaradi povišane vsebnosti organske primesi v sedimentu med Razvoj dachsteinskega apnenca na Krnu v Julijskih Alpah__147 rastjo stromatolitov so te plasti obarvane temneje kot prikamnina, tako da že po bar- vi makroskopsko izstopajo na terenu. Poseben litološki tip kamnine, značilen za nadplimsko okolje, je mikritni in pelmikritni apnenec z izsušitvenimi porami (tab. 1, sl. 1-2, tab. 2, sl. 2-3). Plasti tega apnenca, po Fi s cher j u (1964) imenovane loferit, so precej pogoste v celotnem pro- filu in so debele do 50 cm. Izsušitvene pore merijo do nekaj mm in so z daljšo osjo ori- entirane vzporedno s plastovitostjo kamnine. Pore so nastale z izsuševanjem in krče- njem nekonsolidiranega karbonatnega blata v fazah nadplimskega okolja in dosežejo tudi do 40 % kamnine. Zapolnjuje jih debelozrnati sparit, v večjih porah pa opazu- jemo tudi interni mikritni sediment in gravitacijski (stalaktitični) cement (tab. 2, sl. 3). Slednji je značilen za diagenezo pri meteorskih razmerah, kar kaže na to, da je bil apnenec med sedimentacijo občasno nad nivojem morske gladine. V spodnjem delu profila opazujemo ponekod tanjše plasti onkoidnega apnenca. Onkoidi merijo do 3 cm in kažejo značilno koncentrično zgradbo s številnimi algnimi ovoji (tab. 3, sl. 2-3). Ti so enako kakor pri stromatolitnih laminah rahlo dolomitizi- rani. Večkrat se onkoidi med seboj preraščajo. Nastanek onkoidov je vezan na neko- liko bolj razgibano okolje, na medplimske kanale (tidal channels), kjer so jim tokovi zaradi bibavice omogočali stalno gibanje in koncentrično rast. V celotnem profilu se v več plasteh javljajo tudi korozijske votline (solution cavi- ties), ki merijo od nekaj cm do več dm. Po njih sklepamo na občasne okopnitve dachsteinskega apnenca in predstavljajo paleokraške kanale in votline. Zapolnjuje jih več generacij različno obarvanega sparitnega kalcita, tako da kažejo barvno pisano kokardno teksturo. Posebno lepe in velike korozijske votline so razvite na vrhu Krna, kjer so večkrat zapolnjene tudi z rdečo karbonatno residualno glino (sl. 6, tab. 2, sl. 4). Apnenec s številnimi pisanimi korozijskimi votlinami je zanimiv kot okrasni kamen. Paleogeografske razmere pri nastajanju dachsteinskega apnenca Zgornjetriasne kamnine, ki sestavljajo pretežni del geotektonske enote Južnih Alp, kamor spada tudi območje Krna s posnetim profilom, so nastale na Julijski kar- bonatni platformi, ki je bila formirana na začetku zgornjega triasa. Južno od te plat- forme je bil globljemorski Slovenski bazen, ki se je na predelu osrednjega Posočja med Kobaridom in Srpenico izklinjal. Proti zahodu sta zaradi izklinitve Slovenskega bazena mejili neposredno ena na drugo Julijska in Dinarska karbonatna platforma, ki sta se nadaljevali proti zahodu kot enojna Trento platforma v sosednjo Italijo (Buser & Debeljak, 1996). Sedimentad j ske okoliščine na Dinarski in Julijski karbonatni platformi so bile v zgornjem triasu različne, saj dobimo danes na Dinarski platformi glavni dolomit, ki vsebuje le maloštevilne megalodontidne školjke, medtem ko so te na severno ležeči Julijski platformi v členu C izredno številne (Ogorelec & Rothe, 1993). Za dachsteinski apnenec v posnetem profilu na Krnu je značilno izredno pogostno pojavljanje velikih korozijskih votlin in tempestitov oziroma "nadplimskega kon- glomerata". Ta značilnost se pojavlja v Julijskih Alpah še v sosedstvu Krna na Polov- niku, v dolini Soče jugovzhodno od Bovca in v Bohinju ob cesti iz doline Voj na plani- no Blato. Še posebno so značilne votline, katerih stene obroblja kalcit s conarno strukturo, njen osrednji del pa zapolnjuje rdeča, rumena do vijoličasto obarvana kar- bonatna glina. Na drugih območjih so te votline manj številne in so večidel zapol- 148_ Bojan Ogorelec & Stanko Buser njene le s kalcitom. Zanimivo je, da dobimo korozijske votline le v apnenčevih plas- teh, ki so nastale v podplimskem območju karbonatne platforme in ne segajo nikjer tudi v stromatolitne in laminirane plasti. Izredna pogostnost korozijskih votlin in tempestitov kaže na posebne okoliščine med nastajanjem. Rob karbonatne platforme, na katerem je nastal apnenec na Krnu, je bil najbolj izpostavljen pogostnim dvigovanjem morskega dna oziroma oscilaciji morja in s tem dolgotrajnejšim okopnitvam. Ob tem je prihajalo do intenzivnega za- krasovanja in nastajanja glinenega netopnega ostanka ali fosilnih tal, ki so bila spra- na v osrednje dele korozijskih votlin. Ostalo je še odprto vprašanje, zakaj se te votline ne pojavljajo tudi v stromatolitnih in laminiranih plateh. To bi bilo tudi logično pričakovati, saj so bile ob nastanku kopnega tudi te plasti izpostavljnene prepere- vanju. Ena izmed možnostnih razlag je lahko tudi ta, da so bile stromatolitne plasti zaradi visoke vsebnosti dolomita odpornejše proti zakrasovanju kakor čisti apnenec. Plasti dachsteinskega apnenca v posnetem profilu na Krnu so nastale na skrajnem južnem plitvomorskem robu karbonatne platforme in danes mejijo s tektonskim nar- ivnim kontaktom na južneje ležeče sedimente Slovenskega bazena. Ob nari vnem robu je bil verjetno po njegovem nastanku erodiran le neznatni del plasti dachsteinskega apnenca in je ob tem ostal bolj ali manj ohranjen južni rob nekdanje karbonatne platforme. Na južnem pobočju Velikega Stadorja, jugovzhodno od Krna so ohranjeni še norij- sko-retijski grebenski apnenci, ki predstavljajo lateralni ekvivalent skladovitega dachsteinskega apnenca (Turnšek & Buser, 1991). Tudi ti apnenci kažejo na skra- jni južni rob Julijske karbonatne platforme, ob katerem so ponekod tik ob njenem pregibu v bazen uspevali koralni grebeni. Nastanek tempestitov na območju današnjega Krna zanesljivo ne moremo razloži- ti z neurnimi ali nevihtnimi dogodki. Do meter dolgih in nekaj deset centimetrov de- belih napol litificiranih apnenčevih plošč taki dogodki niso mogli povzročiti. Na teh ploščah tudi ni opaziti sledov krajšega, kaj šele daljšega transporta. Plošč ne ločijo ostre razpoke, ki nastajajo ob površinskem izsuševanju apnenčevega blata. Stiki med njimi so "zaliti" oziroma zapolnjeni s kalcitnim sparitom. Nastanek tempestitov tol- mačiva z občasnimi potresnimi dogodki oziroma sunki, ki so povzročili prelamljanje in zdrsnitve še nekonsolidiranega apnenčevega dna. Potresni sunki so bili najbolj po- gosti in močni prav na robu platforme, ki se je ob strmih prelomih prevešala v južneje ležeči Slovenski bazen. Da je bil ta del karbonatne platforme najbolj izpostavljen tektonskim učinkom, nam pričajo v kasnejšem obdobju (zgornji lias) na njem nastale globoke tenzijske prelomne in široko razprte razpoke, ki so jih zapolnile breče z rdečim vezivom v obliki neptunskih dajkov. Prav ti fenomeni pa so prostorsko vezani na širše območje Krna, kjer dobimo številne plasti tempestitov. Sklep Po litološkem razvoju in po mikrofaciesu lahko sklepamo, da se je noriško-retijski dachsteinski apnenec Krna odlagal v zelo plitvem morju. Strukturni tipi apnenca kažejo, da so se stalno menjavali v nad- in podplimskimi razmerami sedimentacije. Za nad- in medplimsko okolje so značične stromatolitne plasti, izsušitvene pore (lofe- rit) in nadplimski konglomerat. Po klasifikaciji standardnega mikrofaciesa (SME) in klasifikaciji sedimentaci j skih okolij (FB - facies belt, Wilson, 1975; Flügel, 1978) uvrščamo dolomitizirani stromatolitni in loferitni apnenec medplimskega okolja v Razvoj dachsteinskega apnenca na Krnu v Julijskih Alpah__149 SMF 19 in 20 ter v FB 8 do 9 (zaprta platforma in litoralni evaporiti). Glavnina apnenca se je odlagala v zelo plitvi vodi, ki ni bila globlja od 10 ali 20 metrov. Ener- gijski indeks preiskanih vzorcev je nizek do zelo nizek, tako da lahko sklepamo na mirne sedimentaci j ske okoliščine, na zatišni del karbonatne platforme z lokalnimi la- gunami. Apnenci podplimskega okolja kažejo znake standardnega mikrofaciesa (SMF) 8,9,13 in 18 (biomikrit, biosparit, onkoidni grainstone, foraminiferni in algni apnenec) ter pripadajo okolju odprte do delno zaprte karbonatne platforme (FB 7 in 9). Naštete značilnosti in monotoni razvoj dachsteinskega apnenca na obsežnem oze- mlju Alp ter njegova velika debelina kažejo na to, da je bil paleorelief precej raven. Karbonatna platforma se je pogrezala zelo počasi, uravnoteženo s pogrezanjem pa je napredovala tudi sedimentacija. Večkrat je apnenec lokalno okopnel in bil izpostav- ljen paleozakrasovanju, na kar nas opozarjajo številne korozijske votline, zapolnjene s sparitnim kalcitom (sigo) in s karbonatno residualno glino. Podoben razvoj dachsteinskega apnenca s številnimi ciklotemami, kakršen je na Krnu, poznamo iz širšega prostora zahodne Slovenije, posebno iz Julijskih Alp, npr s Kaninskega pogorja, Trente (Jurkovšek, 1987; Jurkovšek et al., 1990), Pokljuke in Kobariškega Stola (Buser, 1986, 1987), Polovnika (Kuščer et al., 1974) ter iz Trnovskega gozda in roba Banjške planote (Ogorelec, 1975, 1988; Ogorelec & Rothe, 1993). Za celotni omenjeni prostor je značilno, da kaže dachsteinski apnenec vse ele- mente klasičnega loferskega razvoja, značilno zanj pa je, da v teh cikotemah pre- vladujeta člena B in C, medtem ko so bazalne breče z residualno glino (člen A) zelo redke. Izredno pogostne korozijske votline so nastale na skrajnem južnem delu Julijske karbonatne platforme, ki je bil najbolj izpostavljen dolgotrajnim okopnitvam oziro- ma vsaj pogosteje kakor severno ležeče lagunsko območje. Ker se te votline pojavljajo samo v apnencu člena C loferske cikloteme, ne pa tudi v členu B (stromatolitne plas- ti), je verjetno vzrok, da zgodnjediagenetsko dolomatizirane stromatolitne plasti niso bile tako intenzivno zakrasele kakor apnenčeve. Nastanek tempestitov povezujemo s pogostnimi potresnimi sunki, ki so prelamljali še nekonsolidirane apnenčeve plasti, katere so zdrsnile ena ob drugi. Do naj intenzivnejših potresnih sunkov je prihajalo prav na meji Julijske karbonatne platforme in južneje ležečega Slovenskega bazena, kjer so nastali dachsteinski apnenci posnetega profila. 150 _Bojan Ogorelec & Stanko Buser References Aigner, T. 1982: Calcareous tempestites: storm - dominated stratification, Upper Muschel- kalk limestones (Middle Trias, SW Germany). In: G. Einsele & E. Seilacher (eds.) - Cyclic and Event Stratification, 180-198, Springer Verl., Berlin. Ai t k en, J. D. 1967: Classification and environmental significance of cryptalgal limestones and dolomites with illustrations from the Cambrian and Ordovician of southwestern Alberta. - Jour Sed. Petrol. 37, 1163-1178, Tulsa. Assereto, R. L. & Kendall, C. G. St. C. 1977: Nature, origin and classification of periti- dal tepee structures and related breccias. - Sedimentology, 24/2, 153-210, Oxford. Babic, Lj. 1968: O triasu Gorskog kotara i susjednih područja. - Geol. vjesnik, 21, 11-18, Zagreb. 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Gebelein, C. D. 1969: Distribution, morphology and accretion rate of Recent subtidal algal stromatohtes, Bermuda. - Jour Sed. Petrol, 39/1, 49-69, Tulsa. Gebelein, C. D. & Hoffman, P. 1973: Algal origin of dolomite laminations in stroma- tolitic limestone. - Jour Sed. Petrol., 43, 603-613, Tulsa. Haas, J. 1994: Lofer cycles of the Upper Triassic Dachstein-Platform in the TDMN, Hun- gary - Spec.Publ. Int. Ass. Sedim., 19, 303-322, Oxford. Herak, M., Sokač, B. & Ščavničar, B. 1967: Correlation of the Triassic in SW Lika, Paklenica and Gorski Kotar (Croatia). - Geol. zbornik, 18/2, 189-202, Bratislava. Illing. L. v.. Wells, A. J. & Taylor, J. C. M. 1965: Penecontemporary dolomite in the Per- sian Gulf. In: L. C.Pray & R. C. Murray (eds.) - Dolomitization and limestone diagenesis, a symposium. SEPM Spec. Pubi., 13, 89-111, Tulsa. Dachstein Limestone from Krn in Julian Alps (Slovenia)__ 153 Jurkovšek, B. 1987: Osnovna geološka karta SFRJ, list Beljak in Ponteba 1:100.000. - Geološki zavod Ljubljana. Jurkovšek, B., Šribar, L., Ogorelec, B. & Kolar - Jurkovšek, T. 1990: Pelagične jurske in kredne plasti v zahodnem delu Julijskih Alp. - Geologija, 31/32, 285-328, Ljubljana. Kuščer, D., Grad, K., Nosan, A. & Ogorelec, B. 1974: Geološke raziskave soške doline med Bovcem in Kobaridom. - Geologija, 17, 425-476, Ljubljana. Matavelli, L., Chilingarian, G. V. & Storer, D. 1969: Petrography and diagenesis of the Taormina formation. Gela oil field, Sicily (Italy). -Sedimentary Geology, 3, 59-86, Amster- dam. Ogorelec, B. 1975: Mikrofacielne, mineraloške in geokemične značilnosti dachsteinskega apnenca na območju Trnovskega gozda in Banjške planote. - Mezozoik v Sloveniji. I. faza. Arhiv GZL in FNT Ljubljana, 31 p., Ljubljana. Ogorelec, B. 1988: Mikrofazies, Geochemie und Diagenese des Dachsteinkalkes und Hauptdolomits in Süd-West-Slowenien, Jugoslawien. - Dissertation, Univ. Heidelberg, 173 p., Heidelberg. Ogorelec, B. & Rothe, P. 1993: Mikrofazies, Diagenese und Geochemie des Dachsteinkalkes und Hauptdolomits in Süd-West-Slowenien. - Geologija, 35, (1992) 81-181, Ljubljana. Sander B. 1936: Beiträge zur Kenntnis der Anlagerungsgefüge (Rhytmische Kalke und Dolomite aus Tirol). - Tschermaksc Mineral. Petrogr Mitt., 46, 27-209, Wien. Selli, R. 1963: Shema geologica delle Alpi Gamiche e Giulie Occidentali. Anali Museo Geol. Bologna, Ser. 2, 30, 136 p.p. Bologna. Turnšek, D. & Buser, S. 1991: Norian-Rhaetian coral reef buildups in Bohinj and Rdeči rob in southern Julian Alps (Slovenia). - Razprave SAZU, IV. razr, 32/7, 215-257, Ljubljana. Z ankl, H. 1967: Die Karbonatsedimente der Obertrias in den nördlichen Kalkalpen. - Geol. Rundschau, 56, 128-139, Stuttgart. Zankl, H. 1971: Upper Triassic carbonate facies in the Northem Limestone Alps. In: G. Müller (ed). Sedimentology of Parts of Central Europe, Guidebook. - 8. Int. Sediment. Con- gress 1971, 147-185, Heidelberg. Wilson, J. L. 1975: Carbonate Facies in Geologie History. - Springer Verl., 471 p., Berlin. 152_ Bojan Ogorelec & Stanko Buser Plate 1 - Tabla 1 1 Intramicritic limestone with shrinkage pores cemented by sparry calcite (loferite) Km 8, X 30 Intramikritni apnenec z izsušitvenimi porami, zapolnjenimi s sparitnim kalcitom (loferit) Km 8, X 30 2 Micritic limestone with numerous shrinkage pores and sheet cracks; member B of the Lofer cyclothem Km2B, x30 Mikritni apnenec s številnimi drobnimi izsušitvenimi porami in razpokami; člen B loferske cikloteme Km 2B, X 30 3 Skeletal alga Solenopora sp. in washed intramicritic limestone Km 14, X 30 Odlomek skeletne alge Solenopora sp. v izpranem intramikritnem apnencu Km 14, X 30 154_ Bojan Ogorelec & Stanko Buser Plate 2 - Tabla 2 1 Detail of dolomitized stromatolitic limestone Krn 12, X 15 Detajl dolomitiziranega stromatolitnega apnenca Krn 12, X 15 2 Loferite; shrinkage pores are infilled with internal micritic silt; geopetal structure Krn 2A, X 40 Loferit; izsušitvene pore geopetalno zapolnjuje interni mikrit Krn 2A, X 40 3 Pelmicritic limestone (loferite) - a detail. Stalactitic cement at the roof of a shrinkage pore (arrows) indicating meteoric diagenetic conditions Krn 5, X 40 Pelmikritni apnenec (loferit) - detajl. V vrhnjem delu pore opazujemo stalaktitni cement (puščice), ki kaže na diagenezo v meteorskih razmerah Krn 5, X 40 4 A detail of smaller solution cavity in washed pelmicritic limestone. Radiaxial fibrous calcite, dog-tooth granular cement (arrows) and internal silt with red residual clay Krn 18, X 15 Detajl manjše korozijske votline v izpranem pelmikritnem apnencu. Vlaknati kalcit s conarno strukturo, zrnati sparit (puščici) ter interni sediment rdeče residualne gline zapol- njujejo votlino Krn 18, X 15 Dachstein Limestone from Krn in Julian Alps (Slovenia) 155 156_ Bojan Ogorelec & Stanko Buser Plate 3 - Tabla 3 1 Spongeous stromatolitic structure with shrinkage pores Krn 22, X 10 Stromatolitna kopuča, prepredena z izsušitvenimi porami Krn 22, X 10 2 Oncoids in washed pelmicritic limestone with shrinkage pores Krn ЗА, X 10 Onkoidi v izpranem pelmikritnem apnencu z izsušitvenimi porami Krn 3A, X 10 3 Vadose pisoids, encrusted with stromatolitic envelopes Krn 28, X 10 Vadozni pisoidi, ki jih preraščajo stromatolitne skorje Krn 28, X 10 GEOLOGIJA 39, 159-157 (1996), Ljubljana Lithofacies characteristics of the Smrekovec volcaniclastics, northern Slovenia Litofacialne značilnosti smrekovških vulkanoklastitov (severna Slovenija) Polona Kralj Geološki zavod Ljubljana Inštitut za geologijo, geotehniko in geofiziko Dimičeva 14, 1000 Ljubljana, Slovenija Key words: andesite volcaniclastics, volcaniclastic turbidites, zeolites Ključne besede: andezitni vulkanoklastiti, vulkanoklastični turbiditi, zeoliti Abstract The Smrekovec mountains are characterised by a widespread occurrence of volcanic rocks of the Upper Oligocene age. Their development is closely related to volcanic activity which resulted in the formation of a submarine stratovolcano complex, emplaced onto pre-Tertiary carbonate basement and locally, on Upper Oligocene marine marls and silts. Magma composition varied with time during volcanic activity. The original tholeiitic magmas very likely underwent a differen- tiation due to low pressure crystal fractionation, resulting in the development of andesitic and finally rhyodacitic magmas. The early stage of volcanic activity was dominantly non-explosive; the main style of fragmentation was autoclastic, relat- ed to chill and quench processes that affected lavas and high-level intrusive bod- ies. During the late-stage of volcanic activity, explosive volcanism was also pre- sent, being most probably related to magmatic and combined magmatic-hydrovol- canic activity. Explosions also seem to have generated or triggered volcaniclastic debris flows and turbidity ash flows. Shallow intrusive bodies (syn-volcanic sills and feeder dykes) were a local source of heat that generated hydrothermal/geothermal conditions in the enclos- ing, water-saturated volcaniclastic sediments. Consequently laumontite, analcime, clinoptilolite, heulandite, thomsonite, yugawaralite, prehnite, pumpellyite, albite, apophyllite, epidote, sphene, chlorite and mixed-layered clay minerals developed as replacements of the primary constituents, interstitial fillings and vein minerals. Kratka vsebina Smrekovško podgorje grade vulkanske kamnine zgornjeoligocenske starosti. Njihov nastanek je vezan na razvoj vulkanskega masiva, sestavljenega iz enega ali več stratovulkanov, ki so delovali v morskem okolju. Podlaga sestoji iz mezozoj- skih karbonatnih kamnin, ponekod tudi iz zgornjeoligocenskih laporjev in meljev- cev. Sestava magme se je med vulkanskim delovanjem spreminjala. Prvotna sesta- 160_Polona Kralj va magme je bila toleitna, vendar se je, najverjetneje zaradi kristalne frakciona- cije, diferencirala, sprva v andezitno in nato v riodacitno. V zgodnjem obdobju je prevladovala neeksplozivna vulkanska dejavnost. Tedaj je bil najpomembnejši na- čin fragmentacije avtoklastičen, vezan na procese nenadnega ohlajanja lave v vod- nem mediju oziroma magme ob intruzijah v plitvo ležeče vlažne sedimente. V po- znejšem obdobju vulkanskega delovanja so se pojavile tudi magmatske in mag- matsko-hidrovulkanske eksplozije. Najverjetneje so le-te povzročile tudi nastanek vulkanoklastičnih debritnih in turbiditnih tokov. Plitvi intruzivi (sin-vulkanski siili in dyki) so predstavljali lokalni izvor toplo- te, zaradi katere so v okolnih, z morsko vodo prepojenih sedimentih iz pornih vod nastajale tople raztopine s povečano vsebnostjo raztopljenih mineralnih snovi. Za- radi njihovega delovanja so začeli kristalizirati zeoliti laumontit, analcim, klinop- tilolit, heulandit, thomsonit, yugawaralit in avtigeni silikati: prehnit, pumpellyit, albit, apofilit, epidot, sfen, klorit in glineni minerali z zmesno strukturo vrste klorit/montmorillonit. Avtigeni minerali nadomeščajo prvotne sestavine kamnin ali pa zapolnjujejo pore in razpoklinske sisteme v kamnini. Introduction The Smrekovec mountains, located in northern Slovenia (fig. 1), are characterised by a w^idespread occurrence of coherent volcanic rocks and volcaniclastic deposits. The complex encompasses an area of approx. 15 sq. km and includes three major mountain peaks, Komen, Krnes and Smrekovec, reaching of 1684 m, 1613 m and 1577 m respectively. The Smrekovec volcanic complex represents a part of a wider vol- canic belt, named the "Smrekovec series", extending along a distance of about 100 km towards the southeast (Mioč, 1978, 1983; Mioč et al., 1986). The Smrekovec volcanics are of Upper Oligocene stratigraphie age, as determined on the basis of foraminifera fauna, encountered in locally underlying marine marls and siltstones (Rijavec, 1966). An early publication on the Smrekovec volcanics appeared at the end of the previ- ous century, when Teller (1898) elaborated the first geological map of the area. Fol- lowing works are mainly related to the period after the Second World War (Hinterlechner-Ravnik;Pleničar, 1967; Mioč, 1978, 1983;Mioč et al., 1986; Osterc, 1976; Kovič&Krošl-Kuščer, 1986;Kovič, 1988). The basement consists mainly of Mesozoic carbonates, occurring as tectonically uplifted blocks on the NW and SE margins of the Smrekovec volcanic complex. A NW-SE trending deep-seated fault of the peri-Adriatic lineament separates this com- plex from the Karavanke tonalité (Mioč, 1983), which is in "sensu stricto" quartz diorite (Zupančič, 1994). The present, rather complicated geological situation in northern and north-east- ern Slovenia is closely associated with global tectonic processes of subduction and collision of the continental African and oceanic European plates and their segmented parts, Apulia and the Pannonian fragment (Oberhauser, 1980; Roy den, 1988; Dercourt et al., 1986). In early Tertiary, Apulia and Europe collided in south-north direction. In early Miocene the Pannonian fragment separated from Apulia and began to escape eastward from the collision zone, whereas the movements of Apulia were directed westwards. The plate movements were accomodated by the peri-Adri- atic lineament (Royden, 1988). The details about the extent and directions of displacements along the peri-Adri- atic lineament in the territory of Slovenia are still uncertain of Slovenia. It also remains undefined whether the Smrekovec volcanism is related to an active conti- nental margin or to one of the collision combinations: island arc - active continental Lithofacies characteristics of the Smrekovec volcaniclastics 161 Fig. 1. The Smrekovec volcanic complex: geologic sketch map (after Mioč, 1983) SI. 1. Poenostavljena geološka karta smrekovškega podgorja (po Mioču, 1983) margin - passive continental margin. Andesitic volcanism may continue during the collision and after its separation from a trench, dipping seismic zone and the geophysical characteristics associated therewith (Gill, 1981). Magma composition gives rather good indications of the tectonic environment. In the Smrekovec volcanic complex, coherent volcanic rocks mainly occur as high-level intrusive bodies and only subordinately as lava flows. Both, coherent and volcani- clastic rocks have undergone appreciable alteration, mainly upon hydrothermal con- ditions (Kovič & Krošl-Kuščer, 1986). The alteration undoubtedly puts severe constraints particularly on geochemical reliability of alkaline elements and alkaline earth abundances. Prior to a description of lithofacieses encountered in volcaniclas- tic deposits, I shall provide some general information on the chemical composition of magma and indicate some problems related to its interpretation. 162 Polona Kralj Chemical composition of coherent rocks Magma composition varied with time during of the Smrekovec volcanic activity. Basalts were the early volcanic products, occurring as submarine lavas and high- level intrusive sills and dykes. Later, andesites predominated and although both, basic and acid varieties are encountered, acid andesites seem to be more common. Acid andesites are mostly vitrophyric and sometimes show perlitic texture. The latest magmas were dacitic and rhyodacitic in composition. They mainly extruded as lava flows and locally underwent extensive autoclastic fragmentation, leading to the for- mation of in situ hyaloclastites. The chemical composition of coherent volcanic rocks (tables 1,2,3) indicates the existence of a volcanic suite which evolved during the the Smrekovec volcanism. A hydrothermal alteration moderately modified the bulk chemical composition of the Smrekovec volcanics. It is known already that the alteration very likely affects the content of alkali metals, alkaline earths (mainly Na, K, Rb, Ba, Sr), light REE and iron oxydes (Thompson, 1973; Honnorez, 1978; Furnes, 1980; Furnes & E 1 - Anbaawy, 1980). For this reason, the diagram using immobile elements SiOg, Ti and Zr (Winchester & Floyd, 1977) was recognised as reliable for the classifi- cation of the Smrekovec volcanics (fig. 2). The Smrekovec volcanics show anomalous abundances of potassium and rubidi- um. The anomalies can be traced by a diagram using K/Rb ratio vs KgO content (fig. 3). K/Rb ratio commonly decreases with an increasing KgO content (Gill, 1981) and Fig. 2. The Zr/TiO, ratios vs SiOg contents (after Winchester & Floyd, 1977) for the Smrekovec volcanics Sl. 2. Diagram odvisnosti med razmerjem Zr/TiOg in vsebnostjo SÌO2 (po Winchester & Floyd, 1977) za preiskane vzorce neeksplozivnih predornin smrekovškega podgorja Lithofacies characteristics of the Smrekovec volcaniclastics 163 Table 1. Chemical composition of the Smrekovec lavas and high-level intrusives. Major elements in wt.% Tabela 1. Kemična sestava smrekovških predornin. Glavne prvine v masnih odstotkih 1. - basalt, northern slopes of Komen (sample Ко-3); 2,- basalt, northem slopes of Smrekovec (sample Sm 34a); 3. - rhyodacite lava flov^^, southern slopes of Komen (sample Sm 81/96C); 4. - basic andesite, southem slopes of Krnes (sample Sm 83/96C); 5. - acid andesite, southem slopes of Krnes (sample Sm 83/96A); 6. - acid andesite, the top of Krnes (sample Sm 16/88); 7. - acid andesite lava flow, southem slopes of Kmes (sample Sm 74/88); 8. - hyaloclastite, southern slopes of Kmes (sample Sm 76/88); Analysed in XRAL Activation Services., Ann Arbor, Michigan 164 Polona Kralj Table 2. Chemical composition of the Smrekovec lavas and high-level intrusives. Trace elements in ppm Tabela 2. Kemična sestava smrekovških predomin. Sledne prvine v mg/g Lithofacies characteristics of the Smrekovec volcaniclastics 165 Table 3. Chemical composition of the Smrekovec lavas and high-level intrusives. Rare earth elements in ppm Tabela 3. Kemična sestava smrekovških predornin. Prvine redkih zemelj v mg/g usually lies above, but parallel to Shaw's main trend (Gill, 1981). Values for K/Rb ratios vs KgO content of the Smrekovec volcanics mostly lie under Shaw's main trend (Shaw, 1968), except in two samples. They even show an inverse trend compared to that observed in several suites of orogenic andesites. E wart (1982) reported that the abundances of Ce and the corresponding Ce/Y ratios are systematically related to the K abundances in many volcanic series from the south-western Pacific subregion. The data of Ce/Y ratios vs Ce abundances for Fig. 3. The K/Rb ratios vs K2O contents (after Gill, 1981) for the Smrekovec volcanics Sl. 3. Diagram odvisnosti med razmerjem K/Rb in vsebnostjo KgO (po Gillu, 1981) za preiskane vzorce neeksplozivnih predornin smrekovškega podgorja 166_Polona Kralj the Smrekovec volcanics (fig. 4) do not show such anomalously scattered values as the K/Rb ratios vs K2O contents. As cerium and yttrium are assumed to be immobile upon zeolite facies conditions, and potassium being mobile and readily incorporated into the zeolite lattice, the anomalous K/Rb ratios vs KgO content can be at least par- tially ascribed to the rock alteration. In orogenic andesites, Th/U ratios likewise tend to increase with K2O, being <2,2 to 4 and >4 in low, medium and high-K suites, respectively (Gill, 1981). Th/U ratios in the Smrekovec volcanics range from 2.3 to 3.5 in spite of the relatively low KgO abundances measured, but do not show any positive correlation with the increasing KgO content. Fig. 4. The Ce abundances vs Ce/Y ratios for the Smrekovec vol- canics SI. 4. Diagram odvisnosti med vsebnostjo Ce in razmerjem Ce/Y za preiskane vzorce neeksplozivnih predornin smrekovškega podgorja The diagram using FeO*/MgO ratio vs SiOg content (FeO* is total iron recalculat- ed as FeO) is widely used to discriminate between tholeiitic and calcalkaline charac- ter of volcanic rocks (Gill, 1981). The FeO*/MgO vs SiOg values of the Smrekovec volcanics (fig. 5) are arranged in a suite which predominantly lies on the line separat- ing tholeiitic and calcalkaline fields. The Smrekovec suite trend compared with the data by Gill (1981) shows an affiliation with either low-K calcalkaline suites or medium-K tholeiitic suites. Other geochemical criteria useful for the recognition of tectonic setting include Ba/Ta, Ba/La and La/Nb ratios (Gill, 1981). These ratio values were also tested for the Smrekovec volcanics (table 4). According to Gill (1981), a Ba/Ta ratio greater than 450 is the single diagnostic geochemical characteristic of arc magmas, whereas Ba/La, La/Th and La/Nb seem to be less significant. The Ba/La ratios of the Smrekovec volcanics are very low, ranging from 100 - 380. As Ba and many other LIL-elements can be mobile during alteration (Thompson, 1973), and on the other hand. Ta is assumed to be a fairly immobile trace element, the Ba/Ta ratios for the Smrekovec volcanics might have been modified by hydrothermal processes. The La/Nb ratios are consistent with the values characteristic of orogenic andesites. Lithofacies characteristics of the Smrekovec volcaniclastics 167 Fig. 5. The FeO*/MgO ratos vs SÍO2 abundances (after Gill, 1981) for the Smrekovec volcanics Sl. 5. Diagram odvisnosti med razmerjem FeO*/MgO in vsebnostjo SÍO2 (po Gillu, 1981) za preiskane vzorce neeksplozivnih predomin smre- kovškega podgorja Table 4. Some trace element ratios in the Smrekovec lavas and high-level intrusives Tabela 4. Razmerja nekaterih slednih prvin v smrekovških predominah 1. - basalt, northern slopes of Komen (sample Ко-3); 2 - basalt, northern slopes of Smrekovec (sample Sm 34a); 3. - rhyodacite lava flow, southem slopes of Komen (sample Sm 81/96C); 4. - basic andesite, southem slopes of Kmes (sample Sm 83/96C); 5. - acid andesite, southern slopes of Krnes (sample Sm 83/96A); 6. - acid andesite, the top of Kmes (sample Sm 16/88); 7. - acid andesite lava flow, southem slopes of Kmes (sample Sm 74/88); Analysed in XRAL Activation Services., Ann Arbor, Michigan The distribution of rare earth elements, normalised to ehondritic values by N a k a- m u r a (1974), shows only moderate enrichment (fig. 6): for the basalt sample, LREE 20-12 X chondritic level, HREE 16-12 x ehondritic level; for dacite and rhyodacite samples, LREE 50-17 x chondritic level, HREE 22-10 x chondritic level, and for andesite samples, LREE 62-16 x chondritic level, HREE 30-10 x chondritic level. The 168 Polona Kralj Fig. 6. The chondrite normalised (after Nakamura, 1974) REE patterns of the Smrekovec vol- canics Sl. 6. Razporeditev prvin redkih zemelj normalizirana na vsebnosti v hondritih (po Nakamuri, 1974) za preiskane vzorce neeksplozivnih predomin smrekovškega podgorja REE distribution is very consistent for the whole suite and shows pronounced nega- tive Eu anomaly (table 4). La/Yb ratios (table 4) are very low compared with the val- ues for orogenic andesites (Gill, 1981; Lopez- Escobar et al., 1977; Poka, 1988; Panto, 1981), indicating limited REE fractionation. Relatively flat REE chondrite-normalised patterns and a pronounced negative Eu anomaly (>10%) are not common in andesites (Gill, 198 l;Lopez-Escobar et al., 1977), but are rather characteristic of tholeiites (Herrmann, 1972; Condie, 1982; Kay&Hubbard, 1978). Although a petrogenesis of the Smrekovec volcanics is far beyond the scope of this work, and the available data rather insufficient, some general statements can be sug- gested. As plagioclases in residue mainly deplete the melt in Sr and Eu (Hanson, 1978), this model can be applied as an option in the case of the Smrekovec volcanics. Some dykes encountered in the Smrekovec volcanic complex are composed almost exclusively of feldspars and could therefore represent late-stage emplacements of the mentioned residual magmas. Some additional fractionation of potassium feldspar would, besides Sr and Eu, contribute to a depletion of K and Ba in the melt relative to the parent. Since REE distributions are very similar for the whole Smrekovec vol- canic suite, the above mentioned feldspar fractionation would explain the anomalous K/Rb, Ba/Ta and Ba/La ratios observed. Lithofacies characteristics of the Smrekovec volcaniclastics_ 169 Description of lithofacieses Recognition of lithofacieses in the Smrekovec volcaniclastic deposits is far from simple. One of the reasons is the scarcity of outcrops due to an abundant vegetation cover, and a furtheron the complex fragmentation and resedimentation process going on in submarine depositional environment. Mioč et al. (1986) already stated, that stratified sequences of volcaniclastic rocks encountered in the Smrekovec volcanic complex, actually represent turbidity current deposits. Field observation and detailed microscopic inspection encompassed in the present study indicate that volcaniclastic turbidite deposits vastly predominate in the area. During the recognition, description and classification of the Smrekovec volcani- clastic deposits contemporary approaches from the works of F i s h e r and S c h m i n- cke (1984), Cas and Wright (1987) and Me Phi e et al. (1993) were taken into account. The lithofacieses of volcaniclastic deposits were subdivided into four main groups: lithofacieses of autoclastic deposits and resedimented hyaloclastite deposits lithofacieses of pyroclastic deposits (?) lithofacieses of volcaniclastic debris flow and turbidite ash flow deposits lithofacieses of reworked turbidite ash flow deposits Lithofacieses of autoclastic deposits and resedimented hyaloclastite deposits Autoclastic fragmentation is closely related to chill and quench processes when lavas enter an aqueous medium or move on a surface composed of water-saturated sediments (Cas & Wright, 1987; Fisher & Schmincke, 1984). Through such non-explosive fragmentation, autobreccias are formed (Mc P hi e et al., 1993). Another group of autoclastic rocks are hyaloclastites, encompassing clastic aggre- gates developed by non-explosive fracturing and disintegration of quenched lavas (Honnorez&Kirst, 1975; Yamagishi, 1987), or parts of intrusions on contacts with wet, unconsolidated host sediments, the so-called intrusive hyaloclastites (Mc Phieet al., 1993). Lithofacies Hb - hyaloclastite breccia Marginal parts of the the Smrekovec coherent volcanic bodies were commonly affected by non-explosive fragmentation. Hyaloclastite breccias are related to frag- mented lava flows - lithofacies Hb(l), and high-level intrusives - lithofacies Hb(i). Lavas were readily fragmented when extruded into the submarine environment (plate 1, fig.l). The lava-sediment basal contacts, observed on a microscopic scale, show smooth and curviplanar boundaries; very frequently no obvious mixing of lava and sediment is present. Brecciated lateral and frontal parts of lava flows are com- posed mainly of larger hyaloclasts, amounting up to 20 cm in diameter. This juvenile lava hyaloclasts are blocky, with curviplanar and sometimes resorbed surfaces; vesic- ulation is very uncommon. In the upper parts of lava flows, autobreccias might be developed. Autoclasts are locally slabby, flow foliated and have jagged ends. 170_Polona Kralj Lateral and front parts of lava flows may contain minor amounts of matrix, con- sisting of finer-grained hyaloclastites and admixed underlying volcaniclastic sedi- ment. Alteration upon zeolite fades conditions is common. Ocassionally, perlite frac- turing is developed due to early hydration processes in the glassy groundmass. Pla- gioclases of hyaloclasts are readily replaced by fine-grained aggregates of albite and the groundmass is altered to microcrystalline quartz, chlorite, mixed-layered clay minerals and opaque oxides. Zeolites, predominantly laumontite, occur as interstitial fillings and vein minerals, rarely they also replace fine-grained clayey matrix of hya- loclastite breccias. High-level intrusive bodies are appreciably more abundant among the Smrekovec coherent rocks. They commonly occur in subaqueous settings when the lithostatic pressure of sedimentary cover exceeds the confining pressure of ascending magma (Cas & Wright, 1987; M c Phi e et al., 1993). In such case, magma intrudes into the pile of sedimentary cover as syn-volcanic sill or feeder dyke. Sudden and intensive heat transfer leads to autoclastic fragmentation, which is particularly pronounced in marginal parts of intrusive bodies. Hyaloclastite breccias related to high-level intrusive bodies are encountered on the top of Komen, as well as in its southern and northern slopes. Autoclasts range in sizes from a few dm to some tenths of mm. The sandy fraction, along with an exten- sively developed interstitial cement, forms the matrix of hyaloclastite breccias (plate 1, fig. 2). Autoclasts are blocky and commonly show curviplanar surfces similar to those produced in frontal and lateral parts of lava flows. Authigenic mineralisation under zeolite fades conditions is particularly pro- nounced in hyaloclastite breccias (plate 1, fig 2), related to high-level intrusions. Pri- mary constituents may be completely replaced by secondary minerals: plagioclases by albite, prehnite, laumontite, pumpellyite or analcime, and the glassy groundmas most commonly by chlorite or interlayered chlorite/smectite, microcrystalline quartz, sphene and albite. Laumontite, prehnite, analcime and thomsonite are fairly abun- dant minerals infilling pore space and crack systems. Lithofacies Hv - hyaloclastites Quench fragmentation of lavas and high-level intrusive bodies due to chilling effects of cooling marine water or water-saturated enclosing sediments may be very efficient producing sand- and granule-sized grains. Hyaloclasts are essentially non- vesicular glassy particles with a distinctly angular shape and curviplanar surfaces (Fisher & Schmincke, 1984; Cas & Wright, 1987; Mc Phie et al., 1993). Hya- loclastites developed "in situ" are strictly monomict and are neither internally organised nor stratified (Yamagishi, 1987; Honnorez & Kirst, 1975). Resedi- mented hyaloclastites may be internally graded and polymict. In situ hyaloclastites developed in the Smrekovec volcanics are localised in close vicinity of lava flows and high-level intrusives. They are mainly monomict, although they may contain very small amounts (up to 8 vol.%) of lithics and pumice. Hyalo- clasts are angular (plate 2, fig. 1), with curviplanar surfaces, glassy with very scarce plagioclase phenocrysts and predominanty non-vesicular A texture of flow foliation in individual hyaloclasts is not uncommon. In many examples the glass is perlitic. Reworked hyaloclastites occur in some cm to a few dm thick, ungraded layers, but they differ from in situ hyaloclastites in much higher content of the admixted compo- Lithofacies characteristics of the Smrekovec volcaniclastics_ 173 nent. Pumice may be particularly abundant attaining up to 40 vol.% of the bulk rock. Resedimented hyaloclastites are fairly eroded. Some scarce, erosional remnants are to be found on the top of the mountain range from Komen to Smrekovec, but also along the southern and northern slopes of the mountain range, at a distance of about 1 km from the mountain peaks. The layers have a declination angle of approx. 25°. Most commonly, resedimented hyaloclastites originate from glassy acid andesite lava flows (table 1, sample 8). Pumice lapilli of similar composition, encountered in resediment- ed hyaloclastites indicate the lavas possibly followed explosive eruptions, producing pyroclastic deposits. In situ hyaloclastites are commonly altered upon hydrothermal and contact meta- morphic conditions to contain laumontite, albite and quartz are the most pronounced new-formed minerals. In resedimented hyaloclastites clinoptilolite and heulandite are abundantly developed; along with smectite and crystobalite they replace volcanic glass in hyaloclasts, pumice and fine-grained matrix. Lithofacies Bp - peperitic breccias Upon an intrusion of magma into wet, unconsolidated sediments, quenched debris may be dynamically mixed with the enclosing sediment. As interstitial water in sedi- ments boils due to magma intrusion, the dispersal of hyaloclasts by fluidisation occurs (Kokelaar, 1982; Cas & Wright, 1987; Mc Phi e et al., 1993). Such mix- tures of quenched debris with the enclosing sediments are called peperites or peperit- ic breccias (Cas&Wright, 1987). Peperitic breccias developed in the Smrekovec volcanic complex are related to intrusions of high-level intrusives. They outcrop on the southern flanks of Krnes, W of the farmhouse Kugovnik and somewhat southwards, near the farmhouse Atelšek. The interpretation of rock formation was given by Jocelyn McPhie and Ray Cas (pers. comm.) during their visit to the Smrekovec mountains in September 1996. Peperitic breccias consist of blocky clasts, characteristic of hyaloclastites, and matrix, composed of fine-grained volcaniclastic sediments (plate 1, fig. 3; plate 2, figs. 2, 3). The blocky clasts are composed of glassy acid andesite, with a fairly com- mon perlitic texture (plate 2, fig. 3). The contacts of blocky clasts and sediment local- ly indicate that resorption and alteration processes were not uncommon. Clasts are essentially non-vesicular and sometimes show the texture of flow foliation. The alteration mainly affected blocky clasts whereas the matrix remained poorly altered. Zeolites - most abundantly laumontite - replace volcanic glass and infill microfissures. The associated authigenic minerals are albite, prehnite, sphene, quar- tz, chlorite and interlayered clay minerals. Lithofacies Vp - peperites Peperites are mixtures of lavas and the enclosing sediment (plate 3, figs. 1, 2). Autoclasts commonly have patchy or globular forms and are very commonly altered to such an extent that their origin became obscured. The alteration is related to hydration reactions and intensive heat transfer from still hot autoclast to the sur- rounding sediment. It is characteristic of this type of alteration that it affected only autoclasts whereas the sediment remained fairly unaltered. Very common secondary minerals replacing autoclasts in peperites are zeolites. 172 Polona Kralj Lithofacieses of pyroclastic deposits Pyroclastic deposits should have both, distinct pyroclastic composition and the mode of transport (Cas & Wright, 1987). In the Smrekovec volcanic complex, pumice-rich tuffs of acid andesitic to dacitic composition are locally encountered (plate 3, fig. 3). However, there is no clear evidence of pyroclastic mode of transport and sedimentation, and the abundance of pumice lapilli only is not an evidence suffi- cient for the recognition of the origin of rocks. Some pumice-rich deposits occur in the sequences of volcaniclastic turbidity flow deposits (fig. 7). In comparison with a typical pyroclastic flow deposit, they lack of cross-bedded fine-grained unit; the coarse-grained unit can be massive or fainty stratified. The upper unit consists of a Fig. 7. Pyroclastic flow deposits (?) sealed in a sequence of volcaniclastic turbidity flow deposits, southem slopes of Krnes. Pyroclastic flow unit (?) can be seen in the lower left half of the photo Sl. 7. Piroklastiti (?) med zaporedjem vulkanoklasti- čnih turbiditov z južnega pobočja Krnesa. Plasti piro- klastitov se vidijo na spodnji levi polovici slike Lithofacies characteristics of the Smrekovec volcaniclastics 173 Fig. 8. Disturbed, fine-grained, horizontally an vaguely laminated tuffs, the upper pyroclastic flow (?) unit. A detail from the previous photo SI. 8. Porušeni, vzporedno in vijugavo laminirani drobnozrnati tufi v vrhnjem de- lu piroklastitov. Detajl iz prejšnje slike fine-grained tuff, horizontally or vaguely laminated (fig. 8). The coarse-grained tuff contains tube pumice of coarse sand- to granule-size; the matrix is subordinate in occurrence and glass shards can not be recognised due to alteration processes. The deposit does not show lenticular geometry. It closely resembles subaqueous volcani- clastic mass-flow deposits (after McPhie et al., 1993). The flow very possibly start- ed as a pyroclastic flow, and was converted to a volcaniclastic mass-flow during its movement in the submarine environment. Lithofacieses of volcaniclastic debris flow and turbidity ash flow deposits Volcaniclastic deposits formed by the settling of volcaniclastic debris flows and turbidity ash flows are particularly widespread on the southern slopes of the moun- tain range. Turbidity ash flow deposits overlie volcaniclastic debris flow deposits and are internally stratified, building fining-upward sedimentary sequences. In the vicinity of Komen, Krnes and Smrekovec peaks, volcaniclastic deposits comprise a considerably larger proportion of volcaniclastic debris flow deposits - often over 75 percent of the total sequence. At a distance of about 2-4 km from the top of the mountain range, volcaniclastic debris flow deposits become much thinner and may even be absent. The proportion of volcaniclastic debris flow deposits decreases to 50 percent or less of the total sequence. In these more distal settings, reworked turbidite deposits are also encountered. 174 Polona Kralj The material contained in volcaniclastic deposits is mainly of autoclastic, subor- dinately of pyroclastic origin, and may be rather heterogenous according to the tex- ture, composition and stage of alteration. Lithofacies Bx - polymict volcaniclastic breccia with mud clasts Polymict volcaniclastic breccia is abundantly encountered in the vicinity of the present outcrops of coherent volcanic rocks near the top of the Komen-Krnes- Smrekovec mountain range. It commonly occurs in the form of tabular bodies, attaining a thickness of a few metres to over ten metres. The deposits are massive, containing angular fragments of coherent volcanics and rounded or angular clasts of mudstone, set in a coarse-grained tuffaceous matrix (fig. 9). The largest fragments may attain up to 5 dm in diameter, but usually they do not exceed 2 dm. The shape and size of larger coherent rock clasts indicate that they probably originate from hyaloclastite breccias and autobrecciated lavas. Juvenile material is very scarce in occurrence. The tabular geometry of polymict volcaniclastic breccias suggest that they are deposits of cohesive volcanic debris flows or lahars. They could have been triggered by volcanic explosions or the effects of earthquakes, gravitational instability on the surface of repose or some larger-scale tectonic displacements. Volcaniclastic debris flows must have been the instrumental in the generation of turbidity ash flows. In Fig. 9. Turbidite ash deposits; southern slopes of Komen. Horizontally stratified division - lithofacies T(h), overlain by volcaniclastic debris flow deposits, lithofacies Bx Sl. 9. Sedimenti turbiditnega toka; južno pobočje Komna. Nad vzporedno plas- tovito enoto litofaciesa T(h) leže sedimenti vulkanoklastičnega debritnega toka litofaciesa Bx Lithofacies characteristics of the Smrekovec volcaniclastics_ 175 volcaniclastic sequences, polymict volcanic breccia commonly overlies turbidite ash deposits and comprises eroded clasts of mudstones from the uppermost turbidite ash division. Due to a lower velocity of volcaniclastic debris flow in relation to the tur- bidity current, the turbidite ash flow deposits underlie the deposits of volcaniclastic debris flow they evolved from (fig. 9). Lithofacies Bt - volcaniclastic tuff-breccias The rocks of this lithofacies type are also related to basal parts of the fining- upward sequences of turbidite ash flow deposits (fig. 10). The bed thickness varies from under 2 dm up to 4 m, but most commonly it ranges between 3-12 dm. The rock structure is massive and the basal contacts erosional. The main constituents are angular fragments of coherent volcanic rocks of diverse origin whereas pumice lapilli are subordinate in occurrence and may locally amount to up to 20% of the bulk rock composition. The matrix is sandy and with respect to the composition closely related to the coarser fraction. Fines are subordinate in occurrence; the rock is mainly grain- supported. Lithofacies Tv(h) - horizontally stratified coarse-grained tuffs The rocks of this lithofacies type are fairly widespread in occurrence throughout the Smrekovec volcanic complex. In well developed turbidity sequences, the division Fig. 10. Distal volcaniclastic turbidite flow deposit; Primož, north-west of Ljub- no. Each sedimentary cycle consists of lithofacieses Bt, T(h), F(h), F(v) and F(m) SI. 10. Distalni sedimenti vulkanoklastičnega turbiditnega toka; Primož nad Ljub- nim. Vsak sedimentaci j ski ciklus sestoji iz litofaciesa Bt, T(h), F(h), F(v) in F(m) 176_Polona Kralj of horizontally stratified coarse-grained tuff overlies massive tuff-breccias of lithofa- cies Bt (fig. 10). The thickness of the coarse-grained tuff division is approx. 0.1-5 m. It may comprise several (over fifty) graded units, 1-20 cm thick. Very commonly one bedding set is composed of distinct subsets, defined by faint stratification. Gradation is for the most part normal. The tuffs vary, according to grain size, from very coarse, granule-rich varieties, to tuffs comprising a fair amount of fine ash. Coarse-grained tuffs are mainly composed of angular rock fragments of diverse composition, texture and stage of alteration. Some sequences are characterised by the occurrence of pumice which may amount to up to 20% of the bulk rock composi- tion, but glass shards are fairly uncommon. The tuffs are predominantly grain-sup- ported; fine-grained matrix, if present, is subordinate and may consist of glassy ash or tuffitic material. Examples of pronounced cementation can be found. Zeolites are the most common cementing minerals that infill interstitial fillings and replace fine- grained matrix. Lithofacieses F(h) and F(v) - horizontally laminated and vaguely laminated fine-grained tuffs The deposits of this litofacies type occupy the uppermost parts of the turbidity sequence and are interpreted as deposits from dilute suspensions, trailing the tur- bidity currents. The lamination is fairly commonly diffuse. In the more ideally devel- oped sequences, the horizontally and vaguely laminated rocks may attain a thicknes of 1-5 dm; syn-sedimentary structures of slumping and sliding occur locally. Lithofacies F(m) - massive fine-grained tuffs Massive fine-grained tuffs occupy the top position in turbidite ash deposits. The thickness varies between a few mm and 25 cm. In near-source deposits they may be absent, but in distal parts they are very common (fig. 11). Lithofacieses of reworked turbidite ash deposits Reworked, fine-grained turbidite ash deposits locally overlie distal, fine-grained turbidite ash deposits. They are related to shallower, possibly shoreline environment, indicated by cross-stratification, bioturbation, mud drapes and abundant organic matter Compositionally they contain some non-volcanic component, very possibly originating from Upper Oligocene siltstones and mudstones. Lithofacies Sv(m) - massive tuffaceous sandstones The occurrence of massive tuffaceous sandstones is scarce. According to their grain-size, they range from fine-grained sandstones to silty sandstones. Locally they are bioturbated. The composition indicates some admixture of non-volcanic material - mainly illite and quartzite, derived from Upper Oligocene clastic sediments. Lithofacies characteristics of the Smrekovec volcaniclastics 177 Fig. 11. Turbidite ash deposits alternating with reworked turbidite ash deposits; Primož, north-west of Ljubno SI. 11. Sedimenti turbiditnega toka, ki se menjavajo z lokalno presedimentiranimi sedimenti turbiditnega toka; Primož nad Ljubnim Lithofacies Sv(t) - through-cross stratified tuffaceous sandstones The deposits of this lithofacies type are related to distal settings. They overlie the horizontally and vaguely laminated fine-grained tuffs of lithofacies types F(h) and F(v). With respect to the grain-size, fine-grained sandstones and silty sandstones pre- dominate. The most common bedforms are antidunes and dunes (fig. 12). According to Cas & Wright (1987) antidunes are deposited by unidirectional current flov^s charac- terised by progressively increasing velocity. Many of the antidune and dune bedforms have thin mud drapes (fig. 12). Mineral composition of the cross-stratified division indicates a partial incorpora- tion of non-volcanic material, characterised mainly by the presence of illite and detritial quartz. Lithofacies M - massive tuffaceous mudstones Massive tuffaceous mudstones of reworked deposits are characterised by mixed, volcanic and non-volcanic mineralogy and local abundance of organic matter. 178 Polona Kralj Fig. 12. Reworked turbidite ash deposits, through cross-stratified sandstone unit - lithofacies Sv(t); Primož, north-west of Ljubno Sl. 12. Lokalno presedimentirani sedimenti turbiditnih tokov, litofacies navzkriž- no plastovitega peščenjaka Sv(t); Primož nad Ljubnim The succession of volcaniclastic deposits related to the settling from turbidite ash flows Volcaniclastic deposits related to the settling from turbidity ash flows are organ- ised in sequences comparable to Bouma's sequence for turbidites (Bo um a, 1962; Cas, 1979). An ideal sequence comprises massive, coarse-grained basal layer (divi- sion a), planar stratified coarse sand (division b), wavy and ripple cross-laminated sand (division c), laminated mud and silt (division d) and massive mud (division e). The development of a volcaniclastic turbidite sequence, encountered in the Smre- kovec volcanic complex, is closely related to the distance of the deposition site from the assumed source. The main present outcrops of coherent volcanics on the moun- tain range top must have been located close to the source of turbidity currents. A widespread occurrence of polymict volcaniclastic breccias deposited from volcani- clastic debris flows or lahars in the vicinity of coherent volcanics also indicates a position was close to the source. Turbidite ash deposits situated closer to the source (fig. 13) comprise coarser- grained massive tuff-breccias (lower division a, lithofacies Bt), horizontally strati- fied, coarse-grained tuff (division b, lithofacies T(h)), and laminated mud and silt (division d, lithofacieses F(h) and F(v)). The upper finely-grained unit (division d) is commonly missing. The stacking of sedimentation units results in the formation of amalgamated turbidites. Slumping and sliding structures are fairly common. Distal turbidite deposits (located approx. 3-4 km further to the south-west are thinner, sometimes lacking the coarser-grained layers (division a). Lithofacies characteristics of the Smrekovec volcaniclastics 179 Fig. 13. Simplified graphic log of the Smrekovec volcaniclastic debris flow^ and turbidite ash deposit: A, proximal deposits and B, distal deposits interbedded with reworked turbidite deposits SI. 13. Shematski profil prek skladovnice sedimentov vulkanoklastičnega debritnega toka in vulkanoklastičnih turbiditnih tokov: A, sedimenti proksimalnih območij in B, sedimenti distal- nih območij, mešani s presedimentiranimi turbiditi Facies model of the Smrekovec volcaniclastics The Upper Oligocene Smrekovec volcanic activity is recorded by the occurrence of coherent volcanic rocks, autoclastic deposits, volcaniclastic deposits and reworked volcaniclastic deposits. Among recently outcropping volcanics, volcaniclastic debris flow and turbidity ash flow deposits predominate. Among coherent volcanic rocks, high-level intrusive bodies are far more abundant than lavas. Early magmas were of basaltic composition, extruding as submarine lava flows or forming high-level intrusive bodies. The chemical composition of trace elements, particularly of rare earths, indicates that basaltic magma most probably underwent a differentiation due to crystal fractionation. Consequently, basaltic andesites, acid andesites and finally rhyodacites evolved in time, forming a volcanic suite. Major element composition is slightly modified due to hydrothermal activity, but trace ele- ment proportions and REE distribution in the Smrekovec coherent volcanics of inter- mediate composition are not very characteristic of orogene andesites. For this reason the tectonic setting still remains ambiguous and may also be related to a setting dif- ferent from convergent plate boundaries. The andesite and dacite occurrence in cen- tral California (Dickinson & Snyder, 1979 a, b) was attributed to local extension 180_Polona Kralj at the plate boundary. The proximity of the peri-Adriatic lineament and the migra- tory junction of Apulia, Europe and the Pannonian fragment could have resulted in local extension and leakage at the plate boundary. The early stage of volcanic activity was dominantly non-explosive. Basalts and basaltic andesites were emplaced as submarine lavas or high-level intrusive bodies. The style of fragmentation was mainly autoclastic, related to chill and quench processes. The late-stage of volcanic activity is characterised not only by non-explo- sive volcanism of acidic andesitic to rhyodacitic composition, but also by explosions, either combined magmatic and hydrovolcanic, or solely magmatic. Juvenile material, chiefly pumice and glass shards, became relatively abundant. Volcanic activity built an edifice of submarine stratovolcano(es) with a significant positive relief, composed of lavas, high-level intrusive bodies, autoclastic deposits, pyroclastic deposits and syn-eruptive resedimented volcaniclastic deposits. Syn-eruptive volcaniclastic resedimentation is rather effective in submarine envi- ronments. Presently outcropping volcanics in the Smrekovec mountains are in fact only erosional remnants of the former, broader volcanic complex and are composed mainly of syn-eruptive resedimented volcaniclastic rocks (fig. 14). Volcaniclastic debris flows and turbidity ash flows may have been generated due to gravitational instability of material resting on steep slopes of strato volcano edifices, and also by volcanic explosions. However, the distinction between deposits of submarine pyro- clastic flows and volcaniclastic turbidity flows is very difficult in general. When pyro- clastic flows enter an aqueous media, they actually behave like volcaniclastic tur- bidity flows (Cas & Wright, 1987). Unlike most turbidite sequences, the lower mas- sive division forms 50 percent or more of the total sequence (Fisher & Schminke, 1984). As single pyroclastic flow deposit commonly reaches several tenths to several hundred metres in thickness (Cas & Wright, 1987; Fisher & Schmincke, 1984). The composition of Smrekovec volcaniclastic rocks is characteristically polymict. The main constituents are lithics which show strong affinity to the Smrekovec coher- ent volcanics and their autoclastic deposits, although textural and compositional dif- ferences may occur in the same sample; sometimes there is also a difference in their state of alteraton. For instance, it is possible to encounter in the same volcaniclastic rock sample relatively unaltered glassy fragments and lithics of high-level intrusive bodies with pumpellyite, prehnite, epidote or laumontite as authigenic minerals. Tuffs, comprising predominantly juvenile material are, very rare, and since they are fairly overgrown, it can not be established whether they have both, a demonstrable pyroclastic mode of fragmentation and transport. In distal parts of the Smrekovec volcanic complex, turbidite ash deposits under- went a reworking process in a shallow-marine environment, in addition to minor admixtures of non-volcanic material, cross-stratification, bioturbation and mud drapes are also characteristic of rocks of this lithofacies. Conclusions The Upper Oligocene Smrekovec volcanic activity is recorded by the occurrence of coherent volcanic rocks, autoclastic deposits, volcaniclastic deposits and reworked volcaniclastic deposits. Besides extrusive rocks, settled in a submarine environment, high-level intrusive bodies were emplaced into unconsolidated, water-saturated vol- caniclastic sediments. Lithofacies characteristics of the Smrekovec volcaniclastics 181 Fig. 14. Idealised facies model for the Smrekovec volcanics SI. 14. Idealizirani facialni model smrekovških vulkanitov 182_Polona Kralj The chemical composition of coherent volcanics indicates that magmas varied with time from basaltic, basaltic andesitic and acidic andesitic to dacitic, forming a volcanic suite. Major element composition is slightly modified due to hydrothermal alteration, but trace element proportions and the REE distribution in the volcanics of intermediate composition are not very characteristic of orogene andesites. I believe that the Smrekovec volcanism must be related to the local extension and leakage at the migratory junction of Apulia, Europe and the Pannonian fragment. During the Smrekovec volcanic activity, extruded lavas, high-level intrusive bod- ies and pyroclastic deposits built a volcanic complex of submarine stratovolcano(es) with significantly elevated relief. The extruded lavas and high-level intrusives underwent quench fragmentation on their contacts with seawater or enclosing water- saturated sediments. In situ hyaloclastites, resting on gravitationaly unstable slopes of the stratovolcano were easily resedimented and consequently resulted in the for- mation of resedimented hyaloclastites. Volcanic debris flow deposits and turbidity ash flow deposits are the most widespread rock type of the Smrekovec volcanic com- plex. Their generation could also be related to the late-stage period of explosive activity. Turbidite ash deposits are locally reworked in a shallow-marine environ- ment. Acknowledgements I am much obliged to the Institute of Geology, Geotechnics and Geophisics for having enabled me to work on this problem. The study was supported by the Ministry of Science and Technology of the Republic of Slovenia. I express my cordial thanks to Prof. Dr. Josip Tišljar from The University of Zagreb, Croatia, for revision of the manuscript and many helpful comments. Litofacialne značilnosti smrekovških vulkanoklastitov__183 Litofacialne značilnosti smrekovških vulkanoklastitov (severna Slovenija) Uvod Smrekovško podgorje grade zgornjeoligocenske vulkanske kamnine. Raztezajo se na površini približno petnajstih kvadratnih kilometrov in predstavljajo osrednji del obsežnejšega vulkanskega pasu, imenovanega tudi smrekovška serija (Mioč, 1978, 1983; Mioč et al., 1986). Najvišje se vzpno vrhovi Komen (1684m), Krnes (1613m) in Smrekovec (1577 m). Zgornjeoligocenska starost predornin je določena na osnovi bio- stratigrafskih raziskav foraminiferne favne, vsebovane v meljastih sedimentih pod- lage (Rijavec, 1966). Prvo geološko delo s tega področja datira iz konca prejšnjega stoletja, kojeTeller (1898) objavil geološko karto lista Prassberg. Po drugi svetovni vojni so tod delovali številni slovenski geologi, bodisi v okviru projekta Osnovne geološke karte I (Hinter- lechner-Ravnik & Pleničar, 1967; Mioč, 1978, 1983; Mioč et al., 1986) kakor tudi raziskav zeolitov (Osterc, 1976; Kovič & Krošl-Kuščer, 1986; Kovič, 1988). Tektonsko okolje nastanka smrekovškega vulkanizma ostaja še vedno nedorečeno. Globalni tektonski procesi, katerih posledica je sedanja zapletena geološka zgradba ozemlja, so nedvomno vezani na zgornjejursko subdukcijo oceanske evropske plošče pod kontinentalno afriško, ki pa je že v začetku terciar j a prešla v kolizijo, usmerjeno od juga proti severu (Oberhauser, 1980; Roy den, 1988; Dercourt et al., 1986). Konec oligocena sta za tektonsko dogajanje na današnjem ozemlju Slovenije pomem- bni predvsem dve manjši litosferni plošči, imenovani Apulija in Panonija, ki sta na- stali z drobljenjem in spajanjem tako afriške kakor tudi evropske plošče. Gibanje Apulije je bilo usmerjeno proti severozahodu, gibanje Panonije pa sprva proti severo- vzhodu in nato proti vzhodu. Gibanje obeh manjših litosfernih plošč se je uravnavalo v peri-adriatski prelomni coni (Roy d en, 1988). Dosedanji maloštevilni podatki o kemizmu smrekovških predornin ne dovoljujejo dorečenih sklepov o njihovem izvoru, geokemični pripadnosti in tektonskem okolju. Vendar je na osnovi vsebnosti glavnih in slednih prvin v preiskanih vzorcih vendarle mogoče reči, da njihov kemizem ni značilen za orogene andezite. Predvsem razpore- ditev prvin redkih zemelj je zelo podobna tako bazaltnim kot tudi andezitnim in da- citnim različkom smrekovškega vulkanskega niza in je zelo netipična za orogene andezite. Najverjetneje je nastanek andezitov in dacitov posledica kristalne frakcio- nacije neke bazaltne magme. Znano je, da se lahko vulkanska aktivnost andezitnega značaja nadaljuje tudi med kolizijo litosfernih plošč in po njej (Gill, 1981), ali pa njen pojav sploh ni neposredno vezan na subdukcijo litosfernih plošč, temveč na lo- kalno ekstenzijo, kakor je to v osrednji Kaliforniji (Dickinson & Snyder, 1979a, 1979 b). Menim, da je smrekovški vulkanizem posledica lokalne ekstenzije med odd- vajanjem Apulije od Panonije oziroma prepustnosti peri-adriatskega lineamenta. Opis litofaciesov vulkanoklastičnih kamnin Smrekovške vulkanoklastične kamnine so bile razporejene v štiri glavne skupine litofaciesov: 184_Polona Kralj litofaciesi avtoklastičnih kamnin in lokalno presedimentiranih hialoklastitov litofaciesi piroklastitov (?) litofaciesi vulkanoklastičnih debritov in turbiditov, litofaciesi lokalno presedimentiranih vulkanoklastičnih turbiditov. Litofaciesi avtoklastičnih kamnin in lokalno presedimentiranih hialoklastitov Avtoklastična fragmentacija je vezana na procese nenadnega ohlajanja, ko se lave izlijejo v vodo ali gibajo po površini vlažnih sedimentov (Cas & Wright, 1987; Fi- sher&Schmincke, 1984). Takšna neeksplozivna fragmentacija pa se pojavlja tudi na stikih plitvo ležečih intruzivov vulkanskega nivoja z okolišnimi vlažnimi sedimen- ti (Mc Phie et al., 1993). Plitvo ležeči intruzivi vulkanskega nivoja se pogosto poja- vljajo v morskih okoljih tedaj, ko je teža sedimentnega pokrova in vodnega stebra večja od tlaka dvigujoče se magme (Mc Phie et al., 1993). Fragmentirani deli plitvo ležečih intruzivov vulkanskega nivoja se imenujejo intruzivni hialoklastiti. Avtobrečirane lave (tabla 1, sl. 1) so med smrekovškimi predominami sorazmerno redke. Mnogo pogosteje je mogoče najti avtoklastične kamnine intruzivnega porekla. Bolj debelozrnati različki so hialoklastične breče (tabla 1, sl. 2), ki vsebujejo hialok- laste z značilnimi, ukrivljenimi ploskvami. Osnova hialoklastičnih breč sestoji iz hialoklastičnega materiala velikosti 0.063-2.0 mm. Hialoklastiti smrekovškega podgorja sestoje iz hialoklastov velikosti drobnih lapilov in vulkanskega pepela. Hialoklasti se od juvenilnih piroklastov ločijo pred- vsem po tem, da skorajda ne vsebujejo votlinic plinskih mehurčkov, oblike zrn so po- gosto zelo oglate, ploskve pa ukrivljene in le malo nazobčane (tabla 2, sl. 1). Presedi- mentirani hialoklastiti niso strogo monomiktni, temveč vsebujejo primes plovca, ki znaša ponekod do 40 vol.%. Prav tako je v nasprotju razliko od pravih hialoklastitov, ki so notranje neorganizirani, v presedimentiranih hialoklastitih opazna plastovitost. Hialoklastične breče, vezane na stike plitvo ležečih intruzivov z okolnimi vlažnimi sedimenti, prehajajo bočno v mešane sedimente, imenovane peperitne breče in peper- iti. Peperitne breče sestoje iz hialoklastov, ki so pomešani z okolnim sedimentom (tabla 1, sl. 3; tabla 2, sl. 2, 3). Mešanje nastaja zaradi fluidizacije osnove okolnih vlažnih sedimentov, v katerih se porne vode zaradi bližine vročega intruziva močno segrejejo. Fluidizacija osnove tako omogoči disperzijo hialoklastov v okolni sediment (M C P h i e et al., 1993). Hkrati s fluidizacijo in segrevanjem pornih raztopin v okolnih sedimentih se pričenjajo ustvarjati lokalni hidrotermalni sistemi, ki povzročajo nas- tanek zeolitov. Peperiti (tabla 3, sl. 1,2) se od peperitnih breč razlikujejo po nepravil- ni, krpasti ali kroglasti obliki hialoklastov (McPhie et al., 1993). Litofaciesi piroklastitov (?) Piroklastiti morajo vsebovati juvenilni material, hkrati pa morajo tudi jasno od- ražati piroklastični način transporta (Cas & Wright, 1987). Med smrekovškimi vul- kaniti se pojavljajo plasti, bogate s plovcem (tabla 3, sl. 3), vendar pa teksture niso dovolj značilne, da bi jih lahko z gotovostjo opredelili kot piroklastite. S plovcem bo- gate plasti izdanjajo med zaporedjem vulkanoklastičnih turbiditov (sl. 7). V primer- javi z značilno zgradbo in zaporedjem sedimentov piroklastičnega toka v plasteh do- mnevnih piroklastitov smrekovškega vulkanskega kompleksa manjkajo spodnji, nav- Litofacialne značilnosti smrekovških vulkanoklastitov__185 zkrižno plastoviti deli drobnozrnatih tufov (Mc Phie et al., 1993). Debelozrnati tufi so masivno grajeni ali pa izražajo samo nakazano vzporedno plastovitost; zgornji deli sestoje iz vzporedno in vijugavo laminiranega drobnozrnatega tufa (sl. 8). Ti sedi- menti so najverjetneje nastali s sedimentacijo iz tokov, ki so po izvoru piroklastični, vendar so se zaradi gibanja v vodnem mediju kmalu spremenili v vulkanoklastične turbiditne tokove. Litofaciesi vulkanoklastičnih debritov in turbiditov Vulkanoklastiti, nastali s sedimentacijo iz debritnih in turbiditnih tokov, so naj- bolj razširjena zvrst kamnin smrekovškega podgorja. Posebno razprostranjeni so na južnih pobočjih Smrekovca, Krnesa in Komna. Te vulkanoklastične kamnine grade skladovnice z zmanjševanjem velikosti zm navzgor V bližini omenjenih vrhov sestoje te skladovnice iz masivnih debritov v njihovih spodnijh delih ter iz plastovitih in laminiranih turbiditov v zgornjih delih. Debriti grade skoraj 75% celotne sekvence. V razdalji 2-4 km od gorskega grebena vrhov Smrekovca, Krnesa in Komna se zmanjša delež debritov v vulkanoklastični turbiditni sekvenci na manj kot 50%, pojavijo pa se tudi drobnozrnati sedimenti, ki so bili lokalno presedimentirani v plitvem morskem okolju. Debriti so zastopani z masivno grajenimi vulkanoklastičnimi tufskimi brečami, ki se pojavljajo v obliki lečastih in ploskastih teles, debelih od manj kot 2 dm do največ 4 m (sl. 9). Stiki s podlago so navadno erozijski. Glavna sestavina vulkanoklastičnih tufskih breč so oglati fragmenti lave in plitvo ležečih intruzivov različne sestave, medtem ko je plovec le maloštevilno zastopan. Drobnozrnate osnove je zelo malo, za- to ima kamnina pretežno klastno podporo. Med turbiditi se pojavljajo vzporedno plastoviti debelozrnati tufi, vzporedno in vijugavo laminirani drobnozrnati tufi in masivno grajeni drobnozrnati tufi (sl. 10, 11). Sestava vulkanoklastičnega materiala je heterogena, v splošnem je vsebnost plovca nizka in le izjemoma presega 10 vol.% celotne kamnine. Litofaciesi lokalno presedimentiranih vulkanoklastičnih turbiditov Lokalno presedimentirani drobnozrnati turbiditi (sl. 12) so vzporedno ali nav- zkrižno plastovito grajeni, pojavljajo se drobne leče mulja (mud drapes), bioturbacija in ponekod tudi organska snov. Sedimenti vsebujejo tudi nevulkanogeno primes, ki najverjetneje izvira iz zgornjeoligocenskih meljevcev. Sklep Zgornjeoligocenski vulkanizem na Slovenskem je zapustil sledove svojega delo- vanja tudi na smrekovškem podgorju. Vulkanizem je deloval v morskem okolju, kjer je nastal vulkanski masiv z enim ali več stratovulkanov in izrazitim pozitivnim relie- fom. Sestava magme se je zaradi frakcijske kristalizacije bazaltne taline s časom spreminjala od bazaltne prek bazaltne andezitne in kisle andezitne do dacitne in tako ustvarila vulkanski diferenciacij ski niz. Tako so se v zgodnjem obdobju vulkanskega delovanja izlili na morsko dno bazalti in bazaltni andeziti. V poznem obdobju vul- 186_Polona Kralj kanskega delovanja so prevladovali kisli andeziti in daciti, ki so se izlili kot lava ali pa so intrudirali v še nekonsolidirane vulkanoklastične sedimente; pojavljale so se tudi vulkanske eksplozije magmatskega ali mešanega magmatsko-hidrovulkanskega značaja. Robovi plitvih intruzivov in lave so se avtobrečirali in mešali z okolnim sed- imentom, zaradi česar je nastal niz avtoklastičnih in mešanih avtoklastičnih-vulka- noklastičnih kamnin. Vulkanski kompleks je bil podvržen nenehni eroziji in presedi- mentaci j i že med samim vulkanskim delovanjem. Kasnejša erozija in živahno tekton- sko delovanje sta oblikovala njegovo današnjo podobo. Zahvala Zahvaljujem se Inštitutu za geologijo, geotehniko in geofiziko, ki mi je omogočil delo pri reševanju te problematike. Raziskave je financiralo Ministrstvo Republike Slovenije za znanost in tehnologijo. Prisrčna zahvala velja prof. dr. Josipu Tišljarju iz Univerze v Zagrebu za recenzijo rokopisa in številne koristne nasvete. Lithofacies characteristics of the Smrekovec volcaniclastics_ 187 References B ouma, A. H. 1962: Sedimentology of some flysch deposits. - Elsevier, 168 pp., Amsterdam. Cas, R. A.F. & Wright, J.V. 1987: Volcanic successions. - Allen; Unwin, 528 pp., London. 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Autobrecciated lava flow; SW of Komen SI. 1. Avtobrečirani lavini tok; jugozahodno pobočje Komna Fig. 2. Hyaloclastite breccia; southem slopes of Krnes SI. 2. Hialoklastična breča; južno pobočje Krnesa Fig. 3. Peperitic breccia; Southern slopes of Krnes, westwards of the farmhouse Kugovnik SI. 3. Peperitna breča; južno pobočje Krnesa, zahodno od kmetije Kugovnik 190 Polona Kralj Plate 2 - Tabla 2 Fig. 1. Angular hyaloclasts in a hyaloclastite from southern slopes of Krnes. Plane polarised light, magnification 14.5 X Sl. 1. Oglati hialoklasti v hialoklastitu z južnega pobočja Krnesa. Presevna polarizirana svetloba, povečava 14.5 x Fig. 2. Peperitic breccia; southern slopes of Krnes, W of the farmhouse Kugovnik. Angular, locally resorbed and flow-foliated andesite clasts in fine-grained matrix. Plane polarised light, magnification 14.5 X Sl. 2. Peperitna breča; južno pobočje Krnesa, zahodno od kmetije Kugovnik. Oglati, sem in tja resorWrani in zaradi tečenja poviti klasti andezita V drobnozrnati osnovi. Presevna polarizirana svetloba, povečava 14.5 x Fig. 3. Peperitic breccia; southern slopes of Krnes, near the farmhouse Atelšek. An angular clast of acid andesite composition with perlitic texture. Plane polarised light, magnification 14.5 x Sl. 3. Peperitna breča z južnega pobočja Krnesa, blizu kmetije Atelšek. Oglat klast kislega andezita kaže perlitsko strukturo. Presevna polarizirana svetloba, povečava 14.5 x Lithofacies characteristics of the Smrekovec volcaniclastics 191 Plate 3 - Tabla 3 Fig. 1. Hyaloclasts of acid andesite (dark-coloured areas) set in a fine-grained matrix. Peperite; southern slopes of Krnes, westwards of the farmhouse Kugovnik. Plane polarised light, magnification 14.5 X SI. 1. Hialoklasti kislega andezita (temnejši deli) v drobnozrnati osnovi. Peperit z južnega pobočja Krnesa, zahodno od kmetije Kugovnik. Presevna polarizirana svetloba, povečava 14.5 x Fig. 2. Irregularly shaped hyaloclasts of an acid andesite (darker areas) set in a fine-grained matrix. Peperite; southern slopes of Krnes, westwards of the farmhouse Kugovnik. Plane polarised light, magnification 14.5 x SI. 2. Nepravilne oblike hialoklastov kislega andezita V drobnozrnati osnovi. Peperit z južnega pobočja Krnesa, zahodno od kmetije Kugovnik. Presevna polarizirana svetloba, povečava 14.5 x Fig. 3. Resedimented(?) pumice-rich tuff; southern slopes of Krnes. Volcanic glass of a tube pumice is replaced by heulandite, quartz and smectite. Plane polarised light, magnification 14.5 x SI. 3. Presedimentirani plovčev tuf z južnega pobočja Krnesa. Vulkansko steklo cevastega plovca je nadome- ščeno s heulanditom, kreme- nom in montmorillonitom. Presevna polarizirana svetloba, povečava 14.5 x GEOLOGIJA 39, 193-214 (1996), Ljubljana Interpretation of Depositional Environment Based on Grain Size Distribution of Sandstones of the Val Gardena Formation in the Area Between Cerkno and Smrečje, Slovenia Interpretacija sedimentacijskega okolja na osnovi porazdelitve velikosti zrn peščenjakov grödenske formacije na območju med Cerknim in Smrečjem, Slovenija Dragomir Skaberne Geološki zavod Ljubljana Inštitut za geologijo, geotehniko in geofiziko Dimičeva 14, 1000 Ljubljana, Slovenija Key words: grain size, depositional environment, sandstone, Val Gardena For- mation, Permian, Slovenia Ključne besede: velikosti zrn, sedimentacijsko okoje, peščenjaki, grödenska formacija, perm, Slovenija Abstract An attempt was made to interpret the mode of transport and the depositional environment of sandstones of the V^al Gardena Formation in the area between Cer- kno and Smrečje by analysis of frequency distribution of lengths of long axes of sections of quartz grains. The examined sandy fraction should have been trans- ported by fluvial currents principally in the saltation and partly the suspension population, and in a smaller degree in the rolling population of grains. Kratka vsebina Z analizo porazdelitve dolgih osi presekov kremenovih zrn peščenjakov grö- denske formacije na območju med Cerknim in Smrečjem smo skušali podati inter- pretacijo načina transporta in sedimentacijskega okolja. Analizirana peščena frakcija naj bi bila transportirana z rečnimi tokovi pretežno v obliki poskakujoče, deloma suspenzijske in v manjši meri kotaleče populacije zm. Introduction The largest continuous belt of the clastic rocks of the Val Gardena Formation in Slovenia extends in the area betw^een Cerkno and Smrečje where they take part of 194_Dragomir Skaberne the Žiri-Idrija nappe unit (Mlakar, 1969). According to the twofold subdivision of the Permian they are attributed to the lower part of the Upper Permian. The beds underlying the Val Gardena Formation consist of dark grey clastic rocks of pre- sumingly Carboniferous age, while their upper part might be of the Lower Permian age. The contact with them is discordant. The passage into overlying beds of the Upper Permian carbonate rocks is gradual and concordant. The most frequent rocks of the Val Gardena Formation are developed in the red sandstone facies, in which conglomeratic and muddy facies are interbedded. As a consequence of their proportion the highest attention in the study of the Val Gardena Formation was attributed to the sandstones. A sandstone as a clastic sedimentary rock consists of terrigenous grains and of chemically precipitated minerals. Its properties depend therefore upon the properties of grains and their fabric. The characteristics of an aggregate of sediment grains (P) can consequently be defined as a function of their composition (c), size (s), shape (sh), and their fabric, described by orientation (o) and packing (p) (Griffiths, 1961, 1967). P = f(c, s, sh, o, p) Determination of one of the given parameters is usually interdependent upon the others. The basic properties of solid cemented rocks that cannot be disintegrated into primary particular grains without the influence on their primary size and shape, can be determined only in thin sections. In this case, an additional variable, the direction of the section across the grain aggregate of the rock must be considered. In the following, only the size, or distribution of sizes, of terrigenous grains in the considered rocks shall be dealt with. The grain sizes in sandstones that can be disintegrated into their primary individ- ual grains is usually determined by sieving. During disintegration the original fabric of grains, that is their orientation (o) and packing (p), is destroyed. From this aspect, the determination of grain size (P^) depends only upon the composition (c), size (s) and shape (sh) of grains. Р3 = f(c, s, sh) Owing to the importance of grain size, or of its distribution in sandstones from the technological, as well as from genetic aspects, various authors (Friedman, 1958, 1962; Adams, 1977; Harrell & Erikson, 1976; Johnson, 1994) attempted to determine the correction factors for transformation of the lengths of long axes of grain sections in thin sections into the grain sizes as determined by sieving. One comes across the problems of the definition of grain size that is dependent upon the method applied (Allen, 1968) and the determination of the "true" size in thin sec- tions, which also represents a mathematical problem. Analysis of the mentioned problems are beyond our frame. Lately they were discussed by Johnson (1994). For a long time in sedimentary petrology, many attempts were made to use the grain size of the sediment for determination of their depositional environment. Grain size distribution in clastic sedimentary rocks is dependent upon the charac- teristics of source rocks, mode of weathering, distribution of grain size in weathered material, mode of transport, conditions of sedimentation and finally of postdeposi- tional processes. An interpretation of the depositional environment by grain size dis- tributions is based upon the assumption that they are predominantly affected by Interpretation of Depositional Environment Based on Grain Size .■.__ 195 hydrodynamic properties of the currents during transport and sedimentation, which would be typical for the distinct depositional environment. The latter represents the most difficult problem, since equal or very similar depositional processes and corre- sponding hydrodynamic conditions may occur in various depositional environments, and thus affect the grain size distributions in a similar manner Therefore the studies of grain size distributions are only in part successful in determining the paleodeposi- tional environments and the depositional processes related with them. In spite of the stated limitations an attempt was made to use the distribution of lengths of long axes of sections of terrigenous quartz grains of the sandy fraction for interpretation of the mode of transport and of the depositional environment of the Val Gardena sandstones in the Cerkno-Smrečje area. Sampling and methodology In total 209 point samples have been analyzed in detail from 18 local profiles-seg- ments (OZS), which all together comprise a thickness of 1234 m. The local profiles-segments can be assembled into five regional composite profiles (OZP): Škofje, Sovodenj, Žirovski vrh, Goli vrh and Lavrovec, as arranged in the direction from NW to SE. They represent the fairly well studied volume of the Val Gardena Formation. The long axes of 200 sections of quartz grains were measured with the micrometer ocular at 150 x magnification in 206 thin sections. The measured quartz grains were randomly selected by point counter The influence of composition on size determina- tion was reduced by measuring the quartz grains only. They are also the principal component in the composition of the Val Gardena sandstones and represent on aver- age 63 % of the population of all terrigenous grains. The lengths of long axes, up to 5 Ф (0.03 mm), were subdivided into classes of 1/4 Ф wide, and below that into classes of 1/2 Ф wied, down to the smallest measured size of about 7 Ф (0.008 mm). The rela- tive and cumulative frequencies were calculated on the basis of these data for the use in further analysis. Results The cumulative frequency distribution curves of the lengths of long axes of sec- tions of quartz grains were drawn in the Ф units on the abscissa and the probability scale on the ordinate. By using the cumulative frequency distribution curves the graphic statistical parameters: graphic mean size (MZ), inclusive standard deviation (SI), inclusive graphic skewness (SKI) and graphic kurtosis (KG) (Folk & Ward, 1957) were determinated. From the same curves also the metric sizes at 1 % (C) and median (MD), as well as quartile deviation (QDa) (Buller&McManus, 1972) were also obtained. The average size (M), standard deviation (S), skewness (SKEW), kurto- sis (KURT), simple measure of skewness (ALFA) and mean cubic deviation (MCD) (Friedman, 1967) were also calculated with the moment estimates. They were cal- culated in spite of difficulties related with the partly open classes in the domains of the smallest and the largest grain sizes, as warned by Folk (1966). The mentioned parameters for individual analyzed samples are listed in table 1, and the descriptive statistics of grain size data are summarized in table 2. 196 Dragomir Skaberne Table 1. Granulometrie parameters Interpretation of Depositional Environment Based on Grain Size .■. 197 Tabela 1. Granulometrični parametri 198 Dragomir Skaberne Interpretation of Depositional Environment Based on Grain Size .■._ 201 200 Dragomir Skaberne Symbols for variables of granulometrie parameters are evident from the text; OZS - segments profiles on the galeries in the uranium mine of Žrovski vrh P 10, H53-54, H52 on the surface KL, RAI, Ra2, RA3, GV, A, B, C, D, E, S and the cores B74, V2, V20, V25 Interpretation of Depositional Environment Based on Grain Size .■._ 203 Oznake spremenljivk, granulometričnih parametrov so razvidne iz tekasta; OZS - segmenti, profili v rovih rudnika urana Žirovski vrh PIO, H53-54, H52, na površini KL, RAI RA2 RAS GV, PR, A, B, C, D, E, S in vrtinah B74, V2, V20, V25 202___Dragomir Skaberne Table 2. Descriptive statistics of some granulomertic parameters Tabela 2. Opisne statistike nekaterih granulometričnih parametrov sprem. - symbols for variables of granulometrie parameters are evident from the text; N - number of cases (samples); min - minimal value; M - main; SD - standard deviation; SK - skewness; KU - kurtosis sprem. - oznake spremenljivk so razvidne iz teksta; N - število enot (vzorcev); min - minimalna vrednost; max - maksimalna vrednost; M - srednja vrednost; SD - standardni odkoln; SK - asimetričnost; KU - sploščenost A relatively good correspondence of the graphic and the moment measures for the mean and the standard deviation can be seen in the table 2. The lengths of long axes of sections of quartz grains in the examined samples vary from 6.09 Ф (0.015 mm) to -2.4 Ф (5.3 mm) v^^ith the mean of 2.16 Ф (0.22 mm). The grains are from poorly to well sorted, on the average moderately well sorted, and their distributions are mainly symmetric. The distributions are very positively to very negatively skewed in the extremes. With respect to the kurtosis, the curves are mostly mesokurtic, but some very platykurtic or very leptokurtic curves could also be observed. The descriptive terms used are related to the quantitative limits as reported by Folk and Ward (1957). In general, the distributions of grain size in the analyzed samples are close to normal with the mean size of 2.16 Ф (0.22 mm) and the average standard deviation of 0.68 Ф(0.094mm). Discussion and interpretation The analysis of the distribution of grain size and its interpretation can be approached in two ways. In the first one, the cumulative frequency distribution curve of grain size is regarded as a whole, and it is attempted to be interpreted on the basis of hydrodynamic characteristics. In the second way, the characteristics of statistic parameters of distributions of grain size from known recent depositional environ- ments are considered and attempts are made to determine empirically the discrimi- nant functions between them. One of the pioneers of the study of cumulative frequency curves was D o e g 1 a s (1946). He found that grain sizes follow the arithmetic probability function, and that their distributions represent a mixture of two or more populations that are the conse- quence of various mechanisms of transport. Inman (1949) distinguished three basic types of transport: rolling, sliding and saltation on the bottom, and suspension. He also contributed some thoughts on the graphic parameters of grain size distribution: mean grain size, sorting (standard deviation) and skewness. Sindowski (1957) con- Interpretation of Depositional Environment Based on Grain Size .■.__ 203 tinued Doeglas's w^ork, but he utilized the log-probability diagrams for represent- ing the cumulative frequency curves, and he empirically subdivided them into groups that belong to sediments of various depositional environments: aeolic, limnic, estuar- ine, littoral and shelf environment. Moss (1962, 1963) believed that the grain size distribution consists of normally distributed subpopulations that are transported by rolling-sliding, saltation and in suspension. The individual subpopulations have their mean size and sorting. Later Vi s her (1965) studied the dependence of grain size dis- tribution on the sedimentary structures in fluviatile deposits and the various deposi- tional processes in diverse depositional environments (Visher, 1969). Based on these concepts an attempt was made to determine the individual genetic populations from the cumulative frequency curves. All three populations of grain sizes, transported by either rolling and sliding (Ro), saltation (Sa) and in suspension (Su), could be determined in the examined samples. Their presence is shown in table 1. In the same table the position of the inflection point between the saltation and sus- pension populations is presented. This point is estimated according to the maximum grain size in suspension {0Su) and the amount of grains that were transported as a bedload (BL %), by rolling or sliding and saltation. The basic cumulative frequency distribution curves are shown in figure 1. The presence of rolling and sliding populations could be established only in 5.26 % of the 209 analyzed samples. When present, their amount varied from 1.5 to 16.0 % with an average of 5.9 %. The minimum size of the mentioned subpopulation is 0.75 Ф (0.6 mm) to 0.2 Ф (0.87 mm), with the mean of 0.43 Ф (0.74 mm). The population of saltation grains was established in 99.04% of the examined samples. This population occurs as a unique population in 40.8%, whereas it is divided in the remaining 58.2 % into two subpopulations (Fig. lb). Their intersection, the inflection point between the two subpopulations of saltation grains, is above the line of unique saltation population in 46.2 % of the cases, and it is marked by a 2 in table 1. This means that the saltation population is positively skewed in 46.2 °/o of the cases, and contains more smaller grains with respect to their expected amount in a symmetrical normal distribution. In 12 % of samples, this intersection between the two subpopulations occurs below the line that represents the unique saltation popu- lation, and is marked by a -2 in table 1. This suggests a negatively skewed saltation population, which contains more larger grains with respect to their expected amount. This indicates a certain hydrodynamic separation even within the population of saltation grains itself, which was already noticed already by Visher (1965, 1969). The distribution of grain size of the analyzed samples showing that the grains transported as bedload by rolling, sliding and saltation in the thin layer in the bot- tom, represents no less than 89.2 % of all grains. The population of suspended grains was established in 52.15 % examined of the samples, and of these only two samples, or 0.05 %, contain only this population of grains. The average amount of suspended population is 10.8%. The amount of sus- pension population is 18.65 % on average, taking into account only the samples con- taining it. The maximum grain size in the suspension population is 2 Ф (0.25 mm) to 4.50 Ф (0.04 mm), and on average 2.90 Ф (0.15 mm), with standard deviation of 0.51 Ф (0.05 mm). With respect to comparisons of presented data (Tab. 1) with those of Visher (1969, 1104, Tab.l), the analyzed distribution of grain sizes are interpreted as a prod- uct of fluvial sedimentary environment. The detailed hydrodynamic interpretations, as made on the basis of grain size distribution by Middleton (1976), Brey er 204 Dragomir Skaberne Fig. 1. Basic groups of cumulative grain size distribution curves for the analyzed samples with genetic interpretation: a) Ro -rolling-sliding, Sa - saltation, and Su - suspension populations of grains; b) cumulative distribution curve represented by a single saltation population (Kl-7.2/1) or by two subpopulations that form a positively skewed (Kl-83.9) and a negatively skewed (PIO 53/500) saltation population Sl. 1. Osnovne skupine kumulativnih porazdelitvenih krivulj velikosti zm analiziranih vzorcev z genetsko interpretacijo: a) Ro - populacija kotalečih - drsečih. Sa - poskakujočih, Su - sus- pendiranih zrn; b) kumulativna porazdelitvena krivulja, predstavljena z eno populacijo (Kl- 7,2/1) ali dvema podpopulacijama, ki sestavljata pozitivno asimetrično (Kl-83,9) in negativno asimetrično (PIO 53/500) populacijo poskakujočih zrn (1979) and others, are beyond the frame of the present study. Only that Middleton (1976) determined the average shear velocity of the transporting medium on the basis of the interruption (position of inflection point) between the populations of grain sizes that are transported by rolling and sliding, and the population of grain sizes in intermittent suspension that coincides with the lower part of the population of salta- tion grains shall be mentioned. In study of dynamics during the transport and sedimentation, Passega (1957, 1964) utilized the ratios between the largest grains at 1 % on the cumulative curve (C) and the median (Md) in metric units, of a larger number of homogenous, but struc- turally diverse samples. The importance of maximum size that should reflect the maximum power of the current, was also recognized by other researchers. Passega (1957, 1964) distinguished two modes of transport: rolling and suspen- sion. He further subdivided the suspension into the graded and homogenous suspen- Interpretation of Depositional Environment Based on Grain Size .■.__205 Sion at the bottom, and the pelagic suspension. The Passega's (1957, 1964) diagram in which the data of analyzed samples were plotted, shows that the prevailing part of the material was transported in form of the graded bottom suspension that could cor- respond to the saltation population (Moss, 1962, 1963; Visher, 1969). Besides the hydrodynamic interpretation of the cumulative frequency distribution function and its importance for the hydrodynamic of the depositional environment the graphic and the moment statistical parameters were also considered. The factor analysis (Skaberne & Smolej, 1981) indicated that the mean grain size and the skewness are interrelated. They are loading the first factor with the highest loadings by skewness. The second factor is defined by the standard deviation and the kurtosis, with the highest loadings by the standard deviation. The scatter- plots of independent variables of the graphic mean grain size (MZ) versus the inclu- sive graphic standard deviation (SI) that separate the aeolic and the fluvial sediments (Friedman, 1961), the beach and the fluvial sediments (Frie dman, 1967); the shore bars and the fluvial sediments (Moiola& Weiser, 1986) were therefore test- ed. According to the discriminant function of Moi ola and Weiser (1968) all the analyzed samples were attributed to the fluvial deposits, whereas the solution on the ground of Friedman's diagrams (1961, 1967) is not significant. A better resolution between the beach and the fluvial deposits provide Friedman's diagrams of the inclusive graphic standard deviation (SI) versus the inclusive graphic skewness (SKI) (Fig. 2a) (Friedman, 1967) by which 85.6 % of studied samples were attributed to the fluvial deposits. An even better resolution was given by the bivari- ate diagram of the moment derived standard deviation (S) versus the mean cubic deviation (MCD) (Fig. 2b), (Friedman, 1967), in which no less than 95.7% of analyzed samples plot in the field of fluvial deposits. An interesting diagram for defining the depositional environments on the basis of granulometrie parameters of the median (MD) versus the arithmetic quartile devia- tion (QDa) in metric units was proposed by Bull er and Mc Manus (1972). The dia- gram discriminates between the "quietwater", fluvial, eolie and beach deposits (Fig. 3). In the envelope of the fluvial sediments plot no less than 97.6 % of the analyzed samples. Conclusion The grain size and its distribution are influenced by a multitude of factors which limits their application for the interpretation of the paleodepositional environment. In case of their use also other relevant criteria, such as the sedimentary structures, spatial succession of facies, fossils, other textural parameters, etc. must be taken into consideration. In the analyzed samples the graphic and the moment derived estimates of the mean grain size and the standard deviation correspond relatively well in spite of open classes on both ends of the distribution curve, whereas the estimates for the skewness and the kurtosis correspond somewhat less well. The distribution of lengths of the long axes of grain sections, as determined in thin sections, can serve in certain cases as a satisfactory approximation to distribu- tions of sizes of real grains. Their representations on log-probability diagrams can be used for interpretation of the mode of transport. Most of the analyzed sandy fraction of the Val Gardena sandstones belongs to the saltation population. The suspension 206 Dragomir Skaberne Fig. 2. Scatterplot for distinguishing between the fluvial and beach clastic sediments: a) plot of graphic standard deviation (SI) versus inclusive graphic skewness (SKI); b) plot of standard deviation (S) versus mean cubic deviation (MCD) (Friedman, 1967) Sl. 2. Bivariatna diagrama za ločitev med rečnimi in obalnimi klastičnimi sedimenti: a) diagram med grafičnim standardnim odklonom (SI) in inkluzivno grafično asimetričnost]o (SKI); b) diagram med standardnim odklonom (S) in srednjim kubiranim odklonom (MSD) (Friedman, 1967) Interpretation of Depositional Environment Based on Grain Size .■. 207 Fig. 3. Scatterplot of metric median (Md) versus quartile deviation (QDa) and their envelopes representing fluvial (1), shore (2), eolian (3) and quiet water (4) environments (Buller & McManus, 1972) Sl. 3. Bivariantni diagram med metrično mediano (Md) in kvartilnim odklonom (QDa) s polji, ki opredeljujejo rečne (1), obalne (2), eolske (3) in mimovodne (4) sedimente (Buller & McManus, 1972) population is present in about one half of the analyzed samples, v^rith the average amount of about 20 %. The rolling and sliding population Mras established only in 5 % of analyzed samples, with the mean amount of about 6 %. On the basis of statistical parameters of the distribution of lengths of long axes of sections of quartz grains of the Val Gardena sandstones in the area between Cerkno and Sovodenj their depositional environment is interpreted as fluvial. This interpre- tation is also confirmed by other criteria such as: sedimentary structures, vertical succession of lithofacies and their lateral correlation, etc. (Skaberne, 1995). Acknowledgements I would like to thank colleagues J. Čar and B. Ogorelec for their valuable com- ments on the manuscript as well as S. Pire for translating it. I would also like to extend my thanks to M. Karer for the drawings. 208_Dragomir Skaberne Interpretacija sedimentacijskega okolja na osnovi porazdelitve velikosti zrn peščenjakov grödenske formacije na območju med Cerknim in Smrečjem, Slovenija Uvod Klastične kamnine grödenske formacije grade v Sloveniji največji sklenjeni pas na območju med Cerknim in Smrečjem, ki pripada idrijsko-žirovski narivni enoti (M 1 a- k a r, 1969). Po dvodelni razdelitvi perma jo uvrščamo v spodnji del zgornjega perma. Talnino grödenski formaciji predstavljajo temno sive klastične kamnine, ki jim pripi- sujemo karbonsko starost, njihov zgornji del pa je lahko tudi spodnjepermske staro- sti. Kontakt s talnino je diskordanten. Prehod v krovnino, ki jo sestavljajo zgornje- permske karbonatne kamnine, pa je postopen in konkordanten. V grödenski formaciji so najbolj zastopani peščeni faciesi. V menjavi z njimi se javljajo še konglomeratni in muljasti faciesi, v katerih so ponekod prisotne tudi kalcitne in dolomitne konkrecije. Glede na zastopanost smo pri raziskavah grödenske formacije posvetili največjo pozornost peščenjakom. Kot klastična sedimentna kamnina je peščenjak sestavljen iz terigenih zrn in ke- mično izločenih mineralov. Zato so njegove lastnosti odvisne od lastnosti zrn in nači- na njihove povezave. Tako lahko značilnost agregata sedimentnih zrn (P) opredelimo kot funkcijo njihove sestave (c), velikosti (s), oblike (sh), orientacije (o) in zgoščenosti (p) (Griffiths, 1961, 1967). P = f (c, s, sh, o, p) Določitev enega podanih parametrov je običajno delno odvisna od drugih. Osnov- ne lastnosti trdno vezanih kamnin, ki se ne dajo dezintegrirati na posamezna zrna brez vpliva na njihovo prvotno velikost in obliko, lahko določamo le v zbruskih. V tem primeru se navedenim pridruži še ena spremenljivka, to je smer preseka prek agregata zrn kamnine. V nadaljevanju se bomo od navedenih lastnosti omejili na velikost oziroma poraz- delitev velikosti terigenih zrn v obravnavanih kamninah. Velikost zrn peskov in peščenjakov, ki se dajo dezintegrirati na posamezna zrna, običajno določamo s sejanjem. Pri dezintegraciji pa uničimo povezave med zrni ozi- roma njihov zlog, ki ga opredeljujemo z orientacijo (o) in zgoščenostjo (p) zrn. Tako je določitev velikosti zrn (P^) odvisna le še od sestave (c), velikosti (s) in oblike (sh) zrn. Рз = f (c, s, sh) Zaradi pomembnosti velikosti zrn oziroma njihove porazdelitve v peščenjakih tako iz tehničnega kakor iz genetskega vidika so različni avtorji (Friedman, 1958, 1962; Adams, 1977; Harrell & Eriksson, 1979; Johnson, 1994) skušali določiti korekcijske faktorje za spremembo v zbruskih določene velikosti presekov zrn v velikosti zrn, opredeljenih s sejalno metodo. Pri tem se srečujemo s problemi definici- je velikosti, ki je odvisna od uporabljene metode (Allen, 1968) in določitvijo "prave" velikosti v zbruskih, ki predstavlja tudi matematični problem. Analiza omenjenih problemov presega naš okvir in jih je v novejšem času obravnaval J o h n s o n (1994). V sedimentni petrologiji se že od nekdaj prizadevajo uporabiti zrnavost sedimenta za določitev okolja njihovega nastanka. Interpretacija sedimentacijskega okolja na osnovi porazdelitve velikosti zrn ■.._209 Porazdelitev velikosti zm v klästiciriH sedfimentnih kamninah je odvisna od zna- čilnosti izvornih kamnin, načina preperevanja, porazdelitve velikosti zrn v preperin- skem materialu, načina transporta, pogojev usedanja in končno od postsedimentaeij- skih procesov. Ugotavljanje sedimentacijskega okolja na osnovi porazdelitve velikosti zrn temelji na predvidevanju, da nanjo najbolj vplivajo hidrodinamične lastnosti to- ka med transportom in sedimentacijo, pri čemer naj bi v določenem sedimentacij- skem okolju vladale zanj značilne hidrodinamične razmere. Prav slednje predstavlja- jo enega največjih problemov, kajti enaki ali zelo podobni sedimentacijski procesi oziroma hidrodinamične razmere nastopajo v različnih sedimentaci j skih okoljih in tako podobno vplivajo na porazdelitve velikosti zrn. Zato so določitve paleosedimentacijskega okolja in sedimentacijskih procesov v njih na osnovi porazdelitve zmavosti le delno uspešni. Kljub navedenim pomislekom smo se odločili poskusiti uporabiti porazdelitve velikosti presekov terigenih kremenovih zrn peščene frakcije za interpretacijo načina transporta in opredelitve okolja sedimentacije grödenskih peščenjakov med Cerknim in Smrečjem. Vzorčevanje in metodologija Analizirali smo 209 točkastih vzorcev iz 18 podrobno posnetih lokalnih profilih - segmentih (OZS), ki zajemajo skupno debelino 1234 m in bolj ali manj reprezenta- tivno predstavljajo raziskovani volumen grödenskih kamnin. Lokalne profile - seg- mente lahko povežemo v pet regionalnih sestavljenih profilov (OZP): Škofje, Sovo- denj, Žirovski Vrh, Goli Vrh in Lavrovec, ki so navedeni v smeri od NW proti SE. V zbruskih smo pri povečavi 150 x z mikrometrskim okularjem merili dolge osi 200 kremenovih zrn. Kremenova zrna so bila slučajno določena s točkovnim števcem. Z izborom ene vrste terigenih, kremenovih zrn smo zmanjšali vpliv sestave na določanje velikosti. V sestavi grödenskih peščenjakov so kremenova zrna tudi najbolj zastopana, saj predstavljajo poprečno 63 % populacije vseh terigenih zrn. Dolžine presekov smo razdelili do velikosti 5 Ф (0.03 mm) na razrede, široke 1/4 Ф, nato pa na razrede 1/2 Ф do najmanjše merjene velikosti 7 Ф (0.008 mm). Na osnovi teh podatkov smo izračunali relativne in kumulativne frekvence, ki so služile za nadaljnjo analizo. Rezultati Na osnovi kumulativnih relativnih frekvenc smo izrisali kumulativne porazdelit- vene krivulje dolgih osi presekov kremenovih zrn s Ф skalo na abcisi in z verjetnostno skalo na ordinati. Iz kumulativne porazdelitvene krivulje smo odčitali vrednosti za izračun grafičnih statističnih parametrov (Folk & Ward, 1957): grafično srednjo vrednost velikosti (MZ), inkluzivni grafični standardni odklon (SI), inkluzivno grafi- čno asimetričnost (SKI) in grafično sploščenost (KG). Poleg tega smo podali velikosti v mm pri 1 % (C) in mediano (MD) ter izračunali kvartilni odklon (QDa) (B u 11 e r & M C M a nus, 1972). Kljub težavam, ki izhajajo iz delno odprtih razredov v območju največjih in najmanjših zrn, na kar opozarja Folk (1966), smo poleg grafičnih sta- tističnih parametrov iz podatkov relativnih frekvenc v razredih 1/4 Ф z momentnim računom izračunali statistične parametre: povprečno velikost (M), standardni odklon (S), asimetričnost (SKEW), sploščenost (KURT), preprosto mero asimetričnosti 210_Dragomir Skaberne (ALFA) in srednji kubirani odklon (MCD) (Friedman, 1967). Navedeni parametri so za posamezne analizirane vzorce zbrani v tabeli 1, opisne statistike granu- lometričnih statističnih parametrov pa podajamo v tabeli 2. Iz tabele 2 je razvidno, da se grafične in momentne vrednosti za srednjo vrednost in standardni odklon sorazmerno dobro ujemajo. Velikost dolgih osi presekov kre- menovih zrn se v raziskanih vzorcih spreminja od 6,0 Ф (0,015 mm) do -2,4 Ф (5,3 mm) in znaša povprečno 2,16 Ф (0,22 mm). Zrna so slabo do dobro, poprečno srednje dobro sortirana, medtem ko so njihove porazdelitve večinoma simetrične. V ekstremih so porazdelitve zelo pozitivno do zelo negativno asimetrične. Če pogledamo sploščenost, vidimo, da so krivulje večidel normalne (mezokurtične), zasledimo pa tudi zelo sploščene ali zelo ošiljene krivulje. Navedeni opisni izrazi se nanašajo na kvantita- tivne meje, ki jih podajata Folk in Ward (1957). V splošnem lahko rečemo, da so porazdelitve velikosti zrn v raziskanih vzorcih relativno normalne s povprečno velikostjo 2,16 Ф (0,22 mm) in povprečnim standardnim odklonom 0,68 Ф (0,094 mm). Razprava Analize porazdelitve velikosti zrn in njene interpretacije se lahko lotimo na dva načina. V enem upoštevamo kumulativno krivuljo porazdelitve velikosti zrn kot celo- to in jo skušamo interpretirati na osnovi hidrodinamičnih značilnosti. V drugem primeru pa obravnavamo značilnosti statističnih parametrov porazdelitev velikosti zrn iz znanih, recentnih sedimentaci j skih okolij in skušamo med njimi empirično ugotoviti diskriminantne funkcije. Eden izmed pionirjev preučevanja oblike kumulativnih krivulj je bil Doeglas (1946). Ugotovil je, da velikosti zrn slede aritmetični verjetnostni funkciji in da nji- hove porazdelitve predstavljajo mešanico dveh ali več populacij, ki so posledice ra- zličnih mehanizmov transporta. Inman (1949) je v transportu prepoznal tri osnovne tipe: kotaljenje ali drsenje in poskakovanje po dnu ter suspenzijo. Poleg tega je podal nekaj misli o grafičnih parametrih porazdelitve velikosti zrn: srednja velikost, sorti- ranost (standardni odklon) in asimetričnost. Sindowski (1957) je nadaljeval delo Doeglasa, vendar je uporabljal log-verjetnostne diagrame prikazovanja kumula- tivnih krivulj in jih glede na obliko empirično razdelil v skupine, ki pripadajo sedi- mentom različnih sedimentacijskih okolij: eolskemu, limničnemu, estuarijskemu, obalnemu in šelfnemu okolju. Moss (1962, 1963) je ugotovil, da je porazdelitev veli- kosti zrn sestavljena iz normalno porazdeljenih podpopulacij, ki se premikajo s kota- Ijenjem in drsenjem, poskakovanjem in v suspenziji. Posamezne podpopulacije imajo svojo povprečno velikost in sortiranost. Kasneje je Visher (1965) v rečnih sedimen- tih preučeval odvisnost porazdelitve velikosti zrn od sedimentnih tekstur in različnih sedimentacijskih procesov v raznolikih sedimentacijskih okoljih (Visher, 1969). Na osnovi teh spoznanj smo skušali v kumulativnih krivuljah opredeliti posame- zne genetske populacije. V raziskanih vzorcih smo lahko določili vse tri populacije velikosti zrn, ki so se premikala s kotaljenjem in drsenjem (Ro), poskakovanjem (Sa) in v suspenziji (Su). Njihova prisotnost je prikazana v tabeli 1. Poleg tega smo v isti tabeli podali položaj prevojne točke med poskakujočo suspenzijsko populacijo. Ta točka je določena z ocenjeno maksimalno velikostjo zrn v suspenziji (Ф Su) in odstot- kom, količino zrn, ki so se transportirala po dnu z mehanizmi talnega transporta (BL %), s kotaljenjem, drsenjem in poskakovanjem. Osnovne oblike kumulativnih porazdelitvenih krivulj so prikazane na sliki 1. Interpretacija sedimentacijskega okolja na osnovi porazdelitve velikosti zrn ■.._211 Izmed 209 raziskanih vzorcev smo ugotovili le v 5,26 % prisotnost kotaleče in drseče populacije. Ob njeni prisotnosti se njena količina spreminja od 1,5 do 16,0 % in znaša povprečno 5,9 %. Minimalna velikost v omenjeni podpopulaciji je 0,75 Ф (0,6 mm) do 0,2 Ф (0,87 mm), povprečno 0,43 Ф (0,74 mm). Populacijo poskakujočih zrn smo zasledili v 99,04 % raziskanih vzorcih. Ta popu- lacija sestavlja enotno populacijo v 40,8 medtem ko se v preostalih 58,2 % razdeli v dve podpopulaciji (sl. 1 b). Presečišče, prevojna točka med obema podpopulacijama poskakujočih zrn je v 46,2 % primerih nad premico enotne podpopulacije v tabeli 1 označeno z 2. To pomeni, da je poskakujoča populacija zrn v 46,2 % primerih pozitivno asimetrična, oziroma vsebuje več manjših zrn v primerjavi z njihovo pričakovano ko- ličino. V 12 % vzorcev je to presečišče med podpopulacijama pod premico, ki predstav- lja enotno populacijo poskakujočih zrn v tabeli 1 označena z 2, kar kaže na negativno asimetrično populacijo poskakujočih zrn, oziroma vsebuje več večjih zrn v primerjavi z njihovo pričakovano količino. To kaže na določeno hidrodinamično separacijo tudi v sami populaciji poskakujočih zrn, na kar je opozoril že Vi s h er (1965, 1969). Če pogledamo porazdelitve velikosti zrn v raziskanih vzorcih, vidimo, da pred- stavljata populaciji zm, ki se premikajo s talnim transportom, s kotaljenjem, drsen- jem in poskakovanjem v tanki plasti po dnu kar 89,2 % vseh zrn. Populacija suspenzijskih zrn je bila ugotovljena v 52,15 % raziskanih vzorcev, od tega vsebujeta dva vzorca ali 0,04 % le to populacijo zrn. Povprečna količina sus- penzijske populacije znaša 10,8 %. V primeru, da analiziramo le vzorce, ki so vsebo- vali suspenzijsko populacijo zrn, znaša njena količina povprečno 18,52 %. Maksimal- na velikost v suspenzijski populaciji je 2 Ф (0,25 mm) do 4,50 Ф (0,04 mm), povprečno 2,90 Ф (0,15 mm) s standardnim odklonom 0,51 Ф (0,05 mm). Glede na primerjavo prikazanih podatkov (Tab. 1) z Visherjevimi (1969, 1104, Tab. 1) interpretiramo analizirane porazdelitve velikosti zrn kot produkt rečnega sedimentacijskega okolja. Podrobnejše hidrodinamične interpretacije, kakor so jih na osnovi porazdelitev velikosti zrn izvajali Middleton (1976), Viard in Breyer (1979) in drugi, pa presegajo naš okvir interpretacije. Kljub temu naj omenimo, da je Middleton (1976) na osnovi prekinitve (položaja prevojne točke) med populacija- ma velikosti zrn, ki se transportiraj o s kotaljenjem in drsenjem, in populacijo zrn v prekinjeni suspenziji (intermitted suspension), ki sovpada s spodnjim delom popu- lacije poskakujočih zrn, določil povprečno strižno hitrost transportnega medija. Pri preučevanju dinamike med transportom in sedimentacijo je Passega (1957, 1964) uporabil razmerja med največjimi zrni pri 1 % na kumulativni krivulji (C) in mediano (Md) v metrskih enotah strukturno raznolikih vzorcev. Pomembnost mak- simalne velikosti, ki naj bi odražala največjo moč toka, so prepoznali tudi drugi raziskovalci. Passega (1957, 1964) je ločil dva načina transporta: kotaljenje in suspenzijo. Suspenzijo je nadalje delil na graduirano in homogeno suspenzijo ob dnu in na pela- gično suspenzijo. Na osnovi posameznih načinov transporta je opredelil obalne, rečne in turbiditne tokove in pelagično suspenzijo. Iz Passegovega diagrama (1957, 1964), v katerega smo vnesli podatke analiziranih vzorcev, je razvidno, da se je pretežni del materiala transportiral v obliki graduirane talne suspenzije (graded bot- tom suspension), kar bi odgovarjalo populaciji poskakujočih zrn (saltation popula- tion) (Moss, 1962, 1963; Visher, 1969). Poleg hidrodinamične interpretacije kumulativne porazdelitvene krivulje in njeno uvrstitev v hidrodinamično sedimentacijsko okolje smo preučevali tudi grafične in momentne statistične parametre. 212_Dragomir Skaberne S faktorsko analizo (Skaberne & Smolej, 1981) smo ugotovili, da sta povprečna velikost in asimetričnost med seboj odvisni in sta vezani na prvi faktor, ki je obremenjen predvsem z asimetričnostjo. Drugi faktor opredeljujeta standardni odklon in sploščenost, pri čemer ga prvi najbolj obremenjuje. Zato smo pregledali le bivariantne diagrame z neodvisnimi spremenljivkami med grafično povprečno velikostjo (MZ) in inkluzivnim grafičnim standardnim odklonom (SI), ki ločuje eolske sipine in rečne sedimente (Friedman, 1961), obalne in rečne sedimente (Friedman, 1967); obalne (obrežne) sipine in rečne sedimente (Moiola& Weiser, 1968). Diskriminantne funkcije MoiolainWeiserja (1968) opredele vse raziskane vzorce kot rečne sedimente, medtem ko določitev na osnovi Friedmanovih dia- gramov (1961, 1967) ni značilna. Boljšo ločljivost med obalnimi in rečnimi sedimenti kažeta Friedmanova diagra- ma med inkluzivnim grafičnim standardnim odklonom (SI) in inkluzivno grafično asimetričnostjo (SKI) (sl. 2a) (Friedman, 1967), v katerem je 85,6% raziskanih vzorcev opredeljenih kakor rečni sedimenti. Še boljšo ločitev kaže bivariantni dia- gram med momentno določenim standardnim odklonom (S) in srednjim kubiranim odklonom (MCD) (sl. 2b), (Friedman, 1967), v katerem je kar 95,7% raziskanih vzorcev v polju rečnih sedimentov. Zanimiv diagram za opredeljevanje sedimentacijskih okolij na osnovi granu- lometričnih parametrov med mediano (MD) in aritmetičnim kvartilnim odklonom (QDa) sta podala Buller in Mc Manus (1972). Ta ločuje "mirnovodne", rečne, eolske in obalne sedimente (sl. 3). V polje rečnih sedimentov pade kar 97,6 % raziskanih vzorcev. Sklepi Na velikost zrn oziroma njihovo porazdelitev vpliva mnogo dejavnikov, zato je njihova uporaba pri interpretaciji paleosedimentacijskega okolja omejena. Ob njiho- vi uporabi v te namene pa moramo upoštevati še vse druge relevantne kriterije, npr. sedimentne teksture, prostorsko sosledje faciesov, fosile, druge strukturne parametre itd. V analiziranih vzorcih se grafični in momentno izračunani podatki srednje veliko- sti in standardnega odklona, kljub odprtim razredom na obeh konceh porazdelitvene krivulje, relativno dobro ujemajo, medtem ko so razlike pri asimetričnosti in sploščenosti nekoliko večje. Porazdelitve velikosti presekov zrn, določenih v zbruskih, so lahko v nekih prime- rih zadovoljiv približek porazdelitvam pravih velikosti zrn. Njihovi prikazi na log - verjetnostih diagramih lahko služijo za interpretacijo načina transporta. Večina razi- skane peščene frakcije grödenskih peščenjakov pripada poskakujoči populaciji. Sus- penzi j ska populacija je prisotna v približno polovici analiziranih vzorcev s povprečno količino približno 20 %. Kotaleča in drseča populacija pa je bila ugotovljena le v 5 % analiziranih vzorcev, s povprečno količino približno 6 %. Na osnovi statističnih parametrov porazdelitev velikosti presekov kremenovih zrn peščenjakov grödenske formacije med Cerknim in Smrečjem interpretiramo okolje njihovega nastanka kot rečno. Tako interpretacijo potrjujejo tudi drugi kriteriji v podrobno posnetih profilih: sedimentne teksture, vertikalno zaporedje litofaciesov in njihova lateralna korelacija itd. (Skaberne, 1995). Interpretacija sedimentacijskega okolja na osnovi porazdelitve velikosti zrn ■.._213 Zahvala Zahvaljujem se kolegom J. Čarju in B. Ogorelcu za koristne pripombe k rokopisu in S. Pireu, ki ga je prevedel. Poleg tega se zahvaljujem M. Karer za risbe. References Adams, J. 1977: Sieve size statistics from grain measurement. - J. Geol., 85, 209-227, Chicago. Allen, T. 1968: Particle size measurements. Chapman and Hall, 248 pp., London. Buller, A. T. & Mc M anus, J. 1972: Simple metric sedimentary statistics used to recognise different environments. - Sedimentology, 18, 1-21, Amsterdam. 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GEOLOGIJA 39, 215-214 (1996), Ljubljana Potencialnost karbonatnih kamnin za nastanek ogljikovodikov V zahodni Sloveniji Carbonate rocks of west Slovenia as potential sources for hydrocarbons Bojan Ogorelec^, Bogdan Jurkovšek^, Drago Šatara^, Gertrud Barić^, Bogomir Jelen^ & +Borislav Kapović'^ Geološki zavod Ljubljana, Inštitut za geologijo, geotehniko in geofiziko, Dimičeva 14, 1009 Ljubljana, Slovenija 2 Gračansko borje 9, 10000 Zagreb, Hrvaška ^ INA-Naftaplin, Služba za laboratorijska istraživanja, Lovinčičeva 1, 10000 Zagreb, Hrvaška 4 INA-Projekt, Savska 88a, 10000 Zagreb, Hrvaška Ključne besede: karbonatne kamnine, ogljikovodiki, mezozoik, Slovenija Key-words: carbonate rocks, hydrocarbons, Mesozoic, Slovenia Kratka vsebina Raziskave zajemajo okolje nastanka in litološke značilnosti ter geokemične in optično-mikroskopske analize organske snovi 196 vzorcev apnencev in dolomitov iz zahodnega dela slovenskih Dinaridov. Dobljeni rezultati so zazdaj orientacijski. Analiziranih je bilo 14 potencialnih formacij različnih starosti, od zgornjega perma do paleocena. Triasne in jurske kamnine vsebujejo v povprečju 0,2 % C in niso potencialne za nastanek nafte in plina. Več C vsebujejo zgomjepermsKi in karnijski apnenci, neugodna v njih pa je sestava kerogena, ker je ta pretežno tere- stričnega izvora. Med deloma potencialne matične kamnine lahko izločimo spod- njekredne črne apnence lagunskega faciesa s Trnovega pri Novi Gorici. Črni ploš- časti in laminirani Komenski in Tomajski apnenec ter plasti Liburnijske formacije kažejo sicer mejne vsebnosti CQj.g, imajo pa neugodno sestavo kerogena. Abstract The research comprises depositional evironment and lithological characteris- tics as well as geochemical and optical analyses of 196 limestone and dolomite samples from Upper Permian to Paleocene age from the western part of Slovenian Dinarides. The obtained results of 14 investigated formations are orientational. Triassic and Jurassic rocks contain 0.2 % C in average and are not potential source rocks for hydrocarbons. The Upper ^rmian and Carman beds contain more CQj.g, but vitrinite constituent of terrestrial origin is unfavorable for the kero- Soavtorji se bomo vedno spominjali našega prijatelja in kolega Bore, ki je preminil pred koncem redakcije tega dela. 216_B. Ogorelec, B. Jurkovšek, D. Šatara, G. Barič, B. Jelen & B. Kapovid gene composition. The black Lower Cretaceous limestone of lagoonal facies from Trnovo near Nova Gorica can be considered as partial potential source rock for hydrocarbons. Black platy and laminated Komen and Tomaj limestone and rocks of the Liburnian Formation indicate a moderate content of C^ but have unfavor- able composition of kerogene. Uvod Raziskave nafte in plina so bile v Sloveniji v zadnjih desetletjih osredotočene v večjem delu na Mursko depresijo, ki pripada zahodnemu delu obsežnega Panonskega bazena. Tak koneept raziskav so narekovala odkritja nafte in plina med drugo svetov- no vojno v okolici Lendave. Leta 1943 je bilo odkrito naftno-plinsko polje Petišovci, takoj za njim pa še polji Dolina in Filovci. Črpanje plina iz globljih slojev petišovske strukture poteka še danes, medtem ko so zaloge iz Doline in Filovec izčrpane. V slovenskem delu Dinaridov so naftno-geološke raziskave potekale bistveno manj intenzivno. V petdesetih in šestdesetih letih so bili v Slovenskem Primorju in na Krasu z geofizikalnimi metodami ugotovljeni nekateri strukturni elementi, ki bi lah- ko predstavljali pasti za ogljikovodike. S površinskimi raziskavami in s stratimetri- jskim snemanjem profilov so bile kasneje raziskane mezozojske karbonatne formaci- je, predvsem njihove biostratigrafske in facialne značilnosti. Izvrtana ni bila nobena naftna raziskovalna vrtina. Najbližje globoke vrtine so tako v Istri pri Rovinju (Ro-1, 4.135 m; Kranjec, 1981) in na italijanskem ozemlju - Amanda 1 v Beneški depresiji (7.305 m, najgloblja "off shore" vrtina v Mediteranu), nadalje vrtina Cesarolo-1 pri izlivu Timava (4.332 m; Ca ti et al., 1989a, 1989b) in 1.400 metrov globoka vrtina SPAN-1 pri Čedadu (Sartorio et al., 1987). V sklepni fazi raziskav je tudi prek 7000 m globoka vrtina Cargnacco pri Udinah. Vse naštete vrtine so bile v naftnem pogledu sicer negativne, posredovale pa so obilico zelo pomembnih stratigrafsko-litoloških in tektonskih podatkov. Rovinjska vrtina in vrtina Amanda sta prevrtali celotno mezoz- ojsko karbonatno skladovnico Istrske platforme in sta končali v permskih karbonat- no-klastičnih plasteh. Skoraj nobenih podatkov pa doslej nismo imeli o vsebnosti organske snovi v kar- bonatnih kamninah in o njihovi potencialni matičnosti. Več podatkov imamo le o nji- hovih facialnih razvojih v slovenskem delu Dinaridov (Pleničar& Premru, 1975; Pleničar & Pavlove C, 1984). Vse predmene o možnosti karbonatnih kamnin za formiranje in migracijo ogljikovodikov so temeljile na opisnih podatkih, kot so "bitu- minozni apnenci ali dolomiti", "duh po bitumnu", "pojavi organske snovi" in podob- no. Glede na slabo poznavanje naftno-geoloških parametrov mezozojskih kamnin v zahodnih Dinaridih je bilo s srednjeročnim Programom naftnih raziskav v Sloveniji za obdobje 1986-1990 predvideno, da dodatno raziščemo tudi njihove potencialne matične lastnosti. V ta namen smo v obdobju 1986-88 raziskali 196 vzorcev apnencev, dolomitov in skrilavcev različnih starosti od zgornjega perma do paleocena. Predmet teh raziskav in objave so predvsem delež organske snovi v kamninah, okolje njihove- ga nastanka, litologija in diagenetske značilnosti ter sestava bitumna. Dobljeni anal- itski rezultati zaenkrat predstavljajo le prepotrebne osnovne podatke za programi- ranje nadaljnjih, dražjih raziskav, kot so geofizikalne meritve in morebitne globoke raziskovalne vrtine. Predstavljeni podatki so rezultat skupnih raziskav Inštituta za geologijo, geot- ehniko in geofiziko iz Ljubljane, INA-Projekta Zagreb in Geokemijskega laboratorija Potencialnost karbonatnih kamnin za nastanek ogljikovodikov v zahodni Sloveniji_2^7 INA-Naftaplin. Terenske in regionalne raziskave so izvajali B. Ogorelec, B. Jurkov- šek, B. Kapovid in D. Satara, geokemične analize in njihovo interpretacijo G. Barić, mikroskopijo organske snovi B. Jelen, kompilacijo podatkov pa B. Ogorelec. Raziskave sta financirala Nafta Lendava in RSS (Raziskovalna skupnost Sloveni- je), današnje Ministrstvo za znanost in tehnologijo Republike Slovenije. Predmet raziskav Potencialnost paleozojskih in mezozojskih karbonatnih kamnin smo raziskovali v zahodnem delu slovenskih Dinaridov, predvsem na Krasu, Trnovskem gozdu, v širši okolici Idrije in v Polhograjskem hribovju (sl. 1). V tem prostoru smo lahko zajeli kamnine od zgornjega perma do paleocena. Pri načrtovanju raziskav smo med poten- cialne matične kamnine uvrstili zgornjepermske apnence in dolomite, karnijske in spodnjekredne apnence ter zgornjekredne tankoploščaste in laminirane apnence Tržaško-komenske planote. Delno smo prištevali sem še jurske in kredne plasti Slovenskega jarka. Omenjene kamnine smo za nastanek ogljikovodikov izločili kot zanimive zaradi njihove temne barve in mikrofaciesa. Temno barvo apnencev in dolomitov pogojujeta razpršena organska snov in pirit, po katerih sklepamo na redukcijske razmere med njihovo sedimentacijo in kasnejše diageneze. Vse naštete plasti so se odlagale v zelo mirnem okolju, večidel v lagunah in zaprtem delu šelfa, nekatere pa v globljem okolju. Vzorce za geokemične analize smo izbrali iz serije štiridesetih stratigrafskih pro- filov in večjih golic. Sami profili niso predmet objave, litologija in facies kamnin ter vsebnost organskega ogljika pa so shematsko prikazane na sliki 2. Vsi raziskani vzorci so bili pregledani z bituminološko-luminiscentno metodo in analizirani na vsebnost organskega ogljika. Na izbranih vzorcih so bile napravljene še piroliza organske snovi (38 vzorcev), sestava bitumna, kromatografske analize nasi- čenih ogljikovodikov in mikroskopska analiza kerogena. Splošno o matičnih kamninah Matične kamnine za nastanek ogljikovodikov so tiste, v katerih se organska snov tako rastlinskega kakor živalskega porekla zaradi anaerobnih pogojev v sedimentu ohrani skozi geološka obdobja. Kazalec vsebnosti organske snovi v kamnini je količi- na organskega ogljika (C^j.^. Z vidika naftne potencialnosti karbonatnih kamnin so zanimive tiste, ki vsebujejo nad 1 % CQj.g. Kamnine, ki vsebujejo 0,3-1 % C , sodijo v obrobno skupino (mejne vrednosti), kamnine z manj kot 0,3 % pa po Kriterijih Robertsonovega geokemičnega laboratorija za naftno matičnost niso perspektivne. Vendar sama vsebnost organske snovi ni zadostna za oceno naftne potencialnosti neke kamnine. Poznati moramo namreč še sestavo organske snovi, njeno poreklo in druge parametre, med njimi tudi termalno evolucijo sedimentacijskega bazena, v katerem je kamnina nastajala. Organsko snov v sedimentu sestavljata bitumen - frakcija, ki je topna v organskih topilih- in kerogen, netopni del organske snovi s strukturo polimerov. Glede na to, da sestavljajo kerogen velike molekule, ga težko analiziramo. To je danes možno s pirolizo (segrevanjem v inertni atmosferi), kjer ta razpada v nižje enote, katere nato lahko ločimo s plinsko in masno kromatografijo. 218 B. Ogorelec, B. Jurkovšek, D. Šatara, G. Barič, B. Jelen & B. Kapovid SL 1.Položaj in starost vzorcev, odvzetih za geokemične raziskave Fig. 1.Locations and age of geochemical samples Zgornji perm - Upper Permian: 1 Vojskarska planota - Rejc, 2 Idrija (rudnik -Hg mine), 3 Masore, 4 Javorjev Dol, 5 Žažar Trias - Triassic: Skitij - Scythian: 6 Želin - Cerkno, 7 Jagrše; Anizij - Anisian: 8 Cerkno - Baba, 9 Polhov Gradec - Sevnik; Ladini] - Ladinian: 10 Oblakov vrh; Karnij - Carnian: 11 Zgornja Trebuša, 12, Huda- južna, 13 Borovnica, 14 Drenov Grič; Norij in reti] - Norian & Rhaetian: 15 Čepovan, 16 Zakojca Jura - Jurassic: (globljevodni razvoj - deep water environment) 17 Hudajužna, 18 Porezen Kreda - Cretaceous: Hauterivij - Hauterivian: 19 Trnovo; Barremij-aptij - Barremian-Aptian: 20 Voglarji, 21 Sabotin, 22 Golac, 23 Markovščina; Albij-cenomanij - Albian- Cenomanian: 24 Povir, 25 Divača, 26 Vrhovlje-Kreplje; Turonij-santonij - Turonian-Santonian: 27 Sežana; Komenski apnenec (ceno- manij - turonij) - Komen limestone (Cenomanian - Turonian): 28 Komen-Škrbina, 29 Tomačevica; Senonij - Senonian (Sežanska formacija - Sežana formation): 30 Sežana, 31 Divača; Tomajski apnenec - Tomaj limestone (zgornji senonij - Upper Senonian): 32 Dutovlje, 33 Križ Kreda-Paleocen (Libumijska formacija) - Cretaceous-Paleocene (Liburnian Formation): 34 Senadole, 35 Štorje, 36 Vremski Britof, 37 Kozina, 38 Hrušica, 39 Sečovlje Sl. 2. Shematski litološki stolpec z raziskanimi formacijami in glavninii geokemičnimi značilnostmi karbonatnih kamnin (delež CQj.g, indeks vitrinitne odsevnosti...). Številke v krogih pomenijo število raziskanih vzorcev posamezne formacije Fig. 2. Shematic lithologie column with investigated formations and main geochemical charac- teristics of carbonate rocks (C^j.^ content, vitrinite reflection index ...). Numbers in circles are indicating nurriber of investigated samples of the formation 220 B. Ogorelec, B. Jurkovšek, D. Šatara, G. Barič, B. Jelen & B. Kapovid SL 3. Van Krevelenov diagram klasifikacije keroge- na na osnovi atomskih razmerij H/C in O/C ter faze diageneze organske snovi. Za primerjavo so podane priMižne vrednosti odsevnosti vitrinita v% (R^ = 0,5-2); po Tissotu (1984) Fig. 3. The Van Krevelen diagram. Chemical classifi- cation of kerogen types according to H/C and O/C atomic ratios and diagenetic stages of organic mat- ter. Vitrinite reflexion data in% are presented for comparison (R = 0.5-2); after Tissot (1984) Na osnovi atomskih razmerij H/C in O/C ločimo tri tipe kerogena, kar ponazarja van Krevelenov diagram na sl. 3 (iz Tissot & Welte, 1984). Za tip I, imenovan tudi "algalno - sapropelski kerogen", je značilno, da nastaja z razgradnjo planktonskih alg in je obogaten z lipidi. Ima visoko H/C razmerje (1,3-1,7) in nizko razmerje O/C (pod 0,1). Ob termalni zrelosti je glavni producent nafte in ga večidel zasledimo v oljnih skrilavcih. Kerogen tipa III ali "huminski kerogen" nastaja z razpadom kopen- skih rastlin oziroma iz lignina, tanina in celuloze. Zanj je značilno nizko začetno razmerje H/C in visoko razmerje O/C. Pri njegovi maturaci]i nastanejo plinasti ogljikovodiki ("gas prone"). Podobno organsko sestavo kot kerogen III imajo tudi nekatere vrste premoga. Kerogen II je mešanica med tipoma I in III in je značilen za morsko okolje. Nastaja z razpadom fito- in zooplanktona in drugih morskih organiz- mov ali terigenih lipidov v redukcijskem okolju. Je najpogostnejši tip kerogena za nastanek nafte. Potencialnost karbonatnih kamnin za nastanek ogljikovodikov v zahodni Sloveniji_2^7 Prehod kerogena v nafto, plin ali premog je funkcija temperature, pritiska in časa. Ta sprememba se prične med 50 in 70°C. Idealne temperature za formiranje nafte so med 80 in 130°C (Tissot et al., 1974), kar pri normalnem geotermičnem gradientu (SOVkni) odgovarja globini 3 - 4.000 metrov. To pomeni, da morajo biti plasti, v kater- ih "dozoreva" nafta, prekrite z debelo skladovnico sedimentov. Pri manjših globinah lahko z biokemičnimi procesi nastane le plin, predvsem metan. Bitumen predstavlja tisti del organske snovi v kamnini, ki je topljiv v organskih topilih. V njem lahko ločimo štiri osnovne sestavine - nasičene ogljikovodike, aromat- ske ogljikovodike, smole in asfaltene. Z analizo teh komponent ugotavljamo izvor in zrelost organske snovi in tiste diagenetske spremembe, ki so rezultat oksidacijskih, mikrobioloških in drugih degradacijskih procesov. Metode, s katerimi raziskujemo zrelost organske snovi v sedimentu, se ločijo na optične in kemične. Med prve sodita meritev barve palinomorf in spor ter odsevnost vitrinitne komponente (R^). Znano je namreč, da je kemična zrelost maceralij funkci- ja temperature. Z zrelostjo se spreminja barva organske snovi od bledorumene prek rumene, oranžne do rjave in črne. Nafta nastaja v tisti fazi zrelosti organske snovi, ki jo označuje indeks vitrinitne odsevnosti R^ = 0,5-1,3 % in je znana kot naftno okno (oil window^ - D o v^, 1977). Pri vrednostih R^ 0,8-2,0 % nastaja najprej "mokri plin" s kondenzati, pri vrednostih R^ = 1,0 do 3,0 % pa "suhi plin", ki je zastopan v glavnem z metanom. Med kemičnimi metodami raziskav organske snovi sta najpomembnejši piroliza in plinska kromatografija. Prva temelji na sežigu organske snovi v inertni atmosferi pri temperaturah med 250 in 550°C. Dobljeni parametri treh plinskih "sunkov" na dia- gramu (S^ do S3) predstavljajo: S^ - nizkotemperaturni sunek (low temperature peak); ta sunek kaže tisti delež prostih ogljikovodikov, ki se izločijo pri nizkih temperaturah (pod 300°C) - bitumen; Sg - visokotemperaturni sunek (high temperature peak) pred- stavlja tisti del organskih sestavin, ki se izločijo pri termični razgradnji kerogena pri '^max (navadno pri temperaturah med 400 in 500°C) - kerogen; S3 preostali del COg po končanem pirolitskem postopku. Iz dobljenih podatkov pirolize dobimo tudi dva zelo pomembna podatka, ki opre- deljujeta tip kerogena - vodikov indeks (HI) kot razmerje mg HC/g CQj.g in kisikov indeks (CI) kot razmerje med mg CO^/g C^^.^. Vsota S^^ + Sg, izražena s kg ogljikovodi- kov na tono kamnine, predstavlja genetski naftni potencial. Kamnine z manj kot 2 kgt'^ ogljikovodikov niso matične kamnine za nafto, imajo le delni potencial za plin, kamnine z do 6 kgt'^ imajo zmeren genetski potencial, tiste z več kot 6 kgt'^ pa so dobre matične kamnine (Tissot&Welte, 1984). Organska snov, ki je bogata s sapropeli, ima visok vodikov indeks (HI) in nizek ogljikov indeks (01), medtem ko imajo kerogeni, bogati s huminsko snovjo, obratno nizek indeks HI in visok ogljikov indeks 01 (E spit alié et al., 1977). V splošnem obstaja zelo dobra korelacija med vodikovim in kisikovim indeksom, izmerjenima pri pirolizi kamnine ter med H/C in O/C razmerjema pri elementarni analizi kerogena. Rezen organsko-kemičnih značilnosti (delež CQj.g, vrste organske snovi in njene termične zrelosti) je za prepoznavanje potencialnih kamnin za nastanek ogljikovo- dikov pomembno tudi poznavanje ugodnih faciesov in njihovih sedimentacijskih okolij (Demaison & Moore, 1980; Moorkens, 1991). Ugodne faciese za nastanek ogljikovodikov v veliki meri sestavljajo sedimenti nizkoenergijskih okolij (low energy depositis); povečini so laminirani in brez znakov bioturbacije. Taki tipi kamnin so laporji, glinovci, mikritni karbonati in kombinacije le-teh, v splošnem pelitni sedimenti. Njihova temna ali čma barva, ki je največkrat 222_B. Ogorelec, B. Jurkovšek, D. Šatara, G. Barič, B. Jelen & B. Kapovid posledica razpršene organske snovi in pigmenta avtigenega pirita, kaže na redukci- jske razmere v sedimentacijskem bazenu. Obstajajo pa tudi primeri, kjer je pirit nastal v fazi kasne diageneze, potem ko je prisotna organska snov že oksidirala in je bila degradirana. Delež pirita je pogosto proporcionalen s količino organske snovi. V sedimetnih, bogatih z organsko snovjo, so večkrat prisotni tudi fosfatni minerali (kažejo na prisotnost hranilnih snovi za mikrooganizme v času sedimentacije), povi- šane v njih pa so tudi vsebnosti nekaterih elementov, kot so U, Cu, Mo in Ni (npr. permski bakrovi skrilavci v severni Nemčiji - "Kupferschiefer"). Dobra kazalca aerobnih in anaerobnih procesov v sedimentacijskem okolju sta tudi paleontološka in palinološka vsebina. V anoksičnem okolju so namreč bentoški fosili odsotni, palinološka združba pa je indikator morskih ali terestričnih rastlin oziroma spor. Eden od kazalcev višje vsebnosti organske snovi v sedimentu je tudi njegova višja radioaktivnost; vzrok temu je, da organska snov veže radioaktivne delce iz morske vode. Zato kažejo sedimenti, bogati z organsko snovjo, visok "gama-ray log" in višjo upornost kakor druge kamnine (to razlagamo z višjo upornostjo organske snovi). Rezultati raziskav Zgornji perm Zgornjepermske apnence in dolomite smo raziskali v treh sklenjenih profilih v širši okolici Idrije in Žirov: na Vojskarski planoti (profil Rejc), pri Masorah in v Ja- vor j evem Dolu pri Sovodnju (sl. 1). Skupno smo analizirali 35 vzorcev. Vojskarska planota predstavlja namreč tisto tektonsko enoto, kjer v zahodni Sloveniji zgorn- jepermske plasti izdanjajo najbolj južno. Planota je del Idrijsko-trnovskega pokrova in je narinjen na kredne apnence in paleogenski fliš Vipavske doline. V obdobju zgornjega perma je pripadalo raziskano območje zahodne Slovenije prostranemu plitvemu šelfu, ki se je razprostiral od severne Italije (Bosellini & Hardie, 1973) proti Madžarski in je potekal tudi prek Slovenije (Slovenska plošča; Bus er, 1989). Črni apnenci in dolomiti leže nad srednjepermskimi klastiti (grödenski peščenjaki) ter navzgor prehajajo zvezno v skitsko karbonatno-klastično zaporedje. Apnenec seje odlagal v zaprtem šelfu lagunskega značaj a(Grad&Ogorelec, 1980; Buser et al., 1986). Lokalno se javljajo tudi plasti satastega dolomita in sadre, ki nakazujejo občasne evaporitne pogoje sedimentacije. Dolomit je večji del nastal med zgodnjo diagenezo s kapilarno koncentracijo ionov v litoralnem nadplimskem okolju. Po favni, mikrofaciesu in makroskopskih teksturah sklepamo na zelo podoben razvoj zgornjepermskih kamnin Idrijsko-žirovskega ozemlja z enako starimi karbon- atnimi plastmi v Liki (Kochansky-Dévidé, 1965, 1979; Sremac, 1991). Analize 35 vzorcev kažejo, da je vsebnost organske snovi v zgornjepermskih apnencih in dolomitih, kljub njihovi temni do črni barvi in ponekod vonju po bitum- nu, precej skromna (sl. 2). Večina vzorcev vsebuje malo organske snovi, od 0,08 do 0,62 % C , v povprečju okrog 0,3 % CQj.g. Le nekaj vzorcev kaže mejne vrednosti z okrog 0,5 % organske snovi. Med apnenci in dolomiti ne opazujemo razlike glede vsebnosti organske snovi. Iz profila Masore ob Idrijci so bili od 22 vzorcev izločeni za pirolitsko analizo štirje (tabela 1). Glede na podatek S2 = O vzorci nimajo naftnega potenciala. Vsebnost bitumna v teh vzorcih je zelo nizka in ne preseže 870 ppm. Kemična analiza enega od Potencialnost karbonatnih kamnin za nastanek ogljikovodikov v zahodni Sloveniji_2^7 apnencev (SP - 93/14) iz srednjega dela formacije je pokazala, da vsebuje bitumen 39 % alkanov, 10 % aromatov, 18 % smol in 33 % asfaltenov. Kromatografska analiza istega vzorca kaže, da v bitumnu prevladujejo ogljikovodiki s sestavo C-^^ do Cg-^, z izrazito prevlado €34 in C25, vsi molekularni parametri kažejo na terestrično poreklo organske snovi. Da bi ugotovili vpliv površinskega preperevanja in izluževanja organske snovi, smo raziskali tri sveže vzorce črnega dolomita iz polja Ljubevč znotraj idrijskega rudišča. Vsebnost organske snovi v preiskanih treh vzorcih zelo niha. Dva vzorca vse- bujeta 0,43 in 0,32 % kar je enak vrstni red kakor različki iste formacije na površini, bistveno več organske snovi (2,34% CQj,g) pa vsebuje vzorec skrilavega dolomita. Optične analize kerogena vzorcev z Vojskarske planote in iz Masor kažejo, da v sestavi kerogena močno prevladujejo maceralije vitrinitne skupine (80-95 %), kar kaže na neugoden organski facies za nastanek ogljikovodikov. Po raziskavi razgrad- nje ligninsko-huminskih delcev v vzorcih in po kromatografskih analizah bitumna lahko sklepamo, da večji del granulozne organske snovi izvira iz kopenskih rastlin. Le v vzorcih iz Javorjevega Dola se javlja tudi kortikularno tkivo alg. Stopnja termi- čne spremembe organske snovi je visoka (R^ = 2,32 %) in predstavlja začetno fazo me- tageneze. Rezultati geokemičnih in optičnih analiz zgornjepermskih plasti idrijskega pros- tora kažejo, da ti apnenci in dolomiti zaradi relativno nizkih vsebnosti CQj.g in sestave kerogena praktično niso potencialne matične kamnine, minimalna pa je tudi prisot- nost sekundarnih ogljikovodikov. Trias Skitske plasti so v osrednji in zahodni Sloveniji razvite delno klastično in delno karbonatno. V spodnjem delu zaporedja se zrnati dolomiti z detritičnim kremenom in sljudo menjavajo s peščenjaki in tanjšimi plastmi ter lečami oolitnega apnenca. Kam- nine kažejo na plitvo oksidacijsko sredino z visoko energijo vode (Grad&Ogorelec, 1980), konodonti pa na vpliv pelagiala (Kolar - Jurkovšek, 1990). V zgornjem delu zaporedja se javlja do 60 m debela skladovnica temnega mikritnega apnenca lagunskega faciesa z znaki občasne litoralne sedimentacije. Iz tega apnenca smo v Jagrščah in Želinu pri Cerknem orientacijsko raziskali le tri vzorce. Apnenec vsebuje od 0,05 do 0,11 % CQj,g, kar je občutno prenizko, da bi spodnjetriasni apnenec zazdaj lahko uvrstili v potencialne matične kamnine. Temna barva kamnine je posledica pir- itnega pigmenta in ne organske snovi. Anizične plasti so v osrednji Sloveniji razvite precej enotno, večidel kot tanko do srednjeplastovit dolomit, tu in tam pa tudi kot apnenec. Dolomit je po strukturi mi- kriten do drobnozrnat sparit. Teksturne oblike, kot so izsušitvene pore, laminit in stromatolit, kažejo na njegovo sedimentacijo v plitvem litoralnem okolju (Grad & Ogorelec, 1980). Dolomitizacija je pretežno zgodnjediagenetskega značaja. Debeli- na anizičnih plasti se na raziskanem ozemlju giblje med 120 in 250 metri. Geokemično smo raziskali le šest vzorcev. V profilu Baba nad Cerknim se med dolomitom javlja nekaj deset metrov debel paket ploščastega in skrilavega biomikrit- nega apnenca temno sive barve. Ta se je odlagal v plitvih lagunah znotraj prostranega karbonatnega šelfa. Vsebnost organske snovi v raziskanih vzorcih dolomita in apnenca se giblje med 0,08 in 0,30 % CQj.g, kar zazdaj ni dovolj za njihovo naftno potencialnost. 224_B. Ogorelec, B. Jurkovšek, D. Šatara, G. Barič, B. Jelen & B. Kapovid Ladinijske plasti: Ob koncu anizičnega obdobja je dotedaj enotna Slovenska kar- bonatna plošča razpadla. Prišlo je do nastanka Dinarske karbonatne plošče na jugu, Julijske plošče na severu in vmesnega Slovenskega bazena, ki se vleče od Tolmina čez osrednjo Slovenijo proti Zagrebu (Buser, 1989). Aktivno tektoniko so spremljali izli- vi predornin in njihovi tufi, ki se javljajo med apnenci. Iz širše okolice Idrije in Cerknega smo na več lokalnostih (Jagršče, Oblakov vrh, Špik) raziskali 12 vzorcev temnega ploščastega apnenca. Stratigrafsko se apnenec javlja med ladinskimi tufi in zrnatim dolomitom cordevolske starosti. Ploščast apnenec je po strukturi laminiran mikrit s pelagično mikrof a vno (radiolariji, kon- odonti, foraminifere). Odlagal se je v nekoliko globljem okolju. Pigment organske snovi in pirit kažeta na redukcijske razmere v sedimentacijskem okolju. Vsebnost organske snovi v preiskanih vzorcih je v mejah med 0,19 in 2,76 % s povprečjem okrog 1,2 %. Večina vzorcev kaže povišano vsebnost organske snovi, ven- dar pirolitska analiza ni potrdila matičnih lastnosti apnenca za nastanek nafte. Viso- ke vrednosti S3 pikov na diagramih pirolitske analize so vezane na povišano vsebnost kisika v kerogenu, višje koncentracije kisika pa običajno vsebuje terestrični, celu- lozno-ligninski tip organske snovi. Na povečani dotok organske snovi s kopnega med sedimentacijo sklepamo tudi po maceralnih analizah kerogena, saj vsebujejo vzorci 75-80 % vitrinitne komponente. Zrelostna stopnja kamnine, določena na osnovi refleksije vitrinita (R^ = 2,76-3,02 %) kaže na visoko metagenetsko fazo spremembe organske snovi, ki se že približuje metamorfni coni. Geokemične analize črnega ladinijskega apnenca z idrijskega prostora torej kaže- jo, da ta ni potencialna matična kamnina za ogljikovodike, kljub relativno visoki vsebnosti CQj.g. Organska snov predstavlja le ostanek terestrične komponente, s katero je bil apnenenc bogat med njegovo sedimentacijo. V karnijskem obdobju se je sedimentacija nadaljevala na celotnem slovenskem ozemlju. Znotraj Dinarske platforme se je v priobrežnih lagunah odlagal biomikritni apnenec, ki je bil lokalno tudi dolomitiziran (npr. Trebuša na Vojskarski planoti, Borovnica). Apnenec je značilno črne barve in ima rahel vonj po bitumnu. Iz profilov pri Borovnici, Drenovem Griču, Orlah in Trebuši smo raziskali 19 vzorcev. Vsebnost organske snovi se v vzorcih giblje med 0,14 in 2,51 % s poprečjem okrog 0,35 % CQj.g, kar je na spodnji meji potencialne matičnosti kamnine. Apnenec ima nizek delež to- pljive bitumenske komponente (pod 200 ppm), iz plinsko-kromatografskih analiz ne- katerih vzorcev pa ugotavljamo degradacijo ogljikovodikov. Organska snov je večidel terestričnega izvora. To se med drugim dopolnjuje tudi s tanjšimi polami premoga pri Orlah in Drenovem griču, ki se javljajo med apnencem (Buser, 1974; Pleničar, 1970). Le manjši del bitumna je morsko-lipidnega izvora. Čmi lapornati apnenci iz Drenovega griča so bili raziskani s pirolitsko analizo, kerogen pa mikroskopsko zaradi odsevnosti vitrinita. Vsi trije vzorci imajo zelo visoko odsevnost (R^^ = 2,2 do 3,2 %), kar kaže na doseženo metagenetsko stopnjo (cona suhega plina) in na zmanjšano možnost generiranja ogljikovodikov. Maceralije sestavljajo vitrinit, vitrodetrinit in mikrinit. Organska snov nima sposobnosti fluores- cence. Vodikov indeks (HI) v istih vzorcih je zelo nizek (6 do 28) in potrjuje visoko termično spremembo organske snovi. Vzorec črnega biomikritnega apnenca iz Trebuše vsebuje nizek delež bitumna (136 ppm), iz njegove plinsko-kromatografske analize pa lahko ugotovimo degradacijo ogljikovodikov. Ta se kaže v povišanem deležu n-alkanov v območju višjih ogljikovo- dikov (Cjg do Cgg), medtem ko je izoalkanov le 12 %. V nekoliko globljem okolju, v Slovenskem jarku so se v karnijskem obdobju odia- Potencialnost karbonatnih kamnin za nastanek ogljikovodikov v zahodni Sloveniji_2^7 gali temni apnenci in skrilavci (amfiklinske plasti). Te smo orientacijsko raziskali s petimi vzorci s Porezna in Hudajužne. V karbonatnem paketu amfiklinskih plasti se črn mikritni apnenec menjava s kalkarenitom, z laporjem in sem in tja s tufskim peščenjakom (Buser & Ogorelec, 1987). Raziskani vzorci vsebujejo od 0,07 do 0,32 % organskega ogljika, kar je prenizko, da bi apnenec uvrstili med potencialno' matičnega za nastanek ogljikovodikov. Več organske snovi vsebuje karnijski mikritni dolomit iz okolice Jagršč pri Idriji. Raziskani vzorec vsebuje 0,61 % CQj.g, kar je mejna vrednost za potencialne matične kamnine. Vodikov indeks, izražen kot razmerje med HC/CQj.g pa je nizek (22) in kaže na to, da dolomit nima lastnosti matične kamnine. Norijsko-retijske plasti so v zahodni Sloveniji razvite kot glavni dolomit (Haupt- dolomit, Main dolomite) in njegov lateralni različek dachsteinski apnenec, na pros- toru Slovenskega jarka pa kot baški dolomit. Vse tri formacije so glede na svetlo barvo kamnine in na njeno strukturo za nafto nezanimive ali zelo malo zanimive. Zato smo orientacijsko raziskali le štiri različke temnejšega pasovitega dolomita s stromatolitno teksturo ter dva različka temnega in drobnozrnatega dolomita baškega razvoja. Glavni dolomit je nastajal v obrežnih in zaprtih delih šelfa (Ogorelec & Rothe, 1992), kjer so se menjavali pod-, nad- in medplimski pogoji sedimentacije, medtem ko je baški dolomit nastal s kasnodiagenetsko dolomitizacijo ploščastega apnenca z rožencem v globljem okolju. Vsebnost CQj.g v raziskanih vzorcih se giblje med 0,06 in 0,61 % s poprečjem 0,15 %, kar je prenizko, da bi glavni dolomit uvrstili med potencialne matične kamnine za nastanek ogljikovodikov. Na meji matičnosti je le en vzorec stromatolitnega dolomita iz Čepovana, ki vsebuje 0,61 % CQj.g. Seveda pa je splošna trditev, da je glavni dolomit za nastanek nafte nezanimiva formacija, samo na podlagi štirih raziskanih vzorcev preuranjena. Podatki imajo strogo orientacijski pomen. Jura Apnenci Dinarske karbonatne platforme so se v zahodni Sloveniji skoz vse jursko obdobje odlagali na plitvem, pretežno odprtem karbonatnem šelfu (Buser, 1979; Orehek & Ogorelec, 1980). Za liasno in doggersko zaporedje je značilna več sto metrov debela skladovnica svetlega oolitnega in biosparitnega apnenca, v spodnjem malmu pa so bili na območju Trnovskega gozda obsežni koralni grebeni (Turnšek, 1966; Turnšek et al., 1981). Glede na strukturne tipe in facialne značilnosti jurski apnenec Dinarske platforme ne uvrščamo med potencialne matične kamnine. Zato jih v tej fazi raziskav geokemično tudi nismo raziskali. Kot potencialno matično kamnino jurskega obdobja smo izločili le okrog 150 me- trov debel paket črnih apnencev in karbonatnih skrilavcev iz Slovenskega jarka. Iz profilov na Poreznu, pri Zalem Logu in pri Hudajužni smo zato orientacijsko raziska- li osem vzorcev lapornih apnencev in glinovcev. Po strukturi je apnenec mikriten in pogosto vsebuje bogato favno radiolarijev in krinoidnih ploščic. Po faciesu kamnine sklepamo, da so se ti apnenci in glinovci odlagali v globljem in mirnem okolju, kjer so bili redukcijski pogoji. Glinovec vsebuje od 0,16 do 0,27 % CQj.g, apnenec pa od 0,32 do 0,48 % , kar ga uvršča na spodnjo mejo matičnosti. Domnevamo lahko, da sta bila v sedimentacijskem okolju zmanjšana biloška aktivnost in prekinjen dotok terigene- ga materiala, kar se odraža v nizkem deležu CQj.g Zelo nizka je v apnencu vsebnost bi- tumna. Ta se giblje med 100 in 200 ppm, zato teh kamnin zazdaj nismo raziskali z večjim številom vzorcev. 226_B. Ogorelec, B. Jurkovšek, D. Šatara, G. Barič, B. Jelen & B. Kapovid Kreda Pri načrtovanju naftno geoloških raziskav karbonatnih kamnin Slovenskega Pri- morja in zahodne Slovenije, smo se najbolj obetavnih rezultatov nadejali pri krednih plasteh, predvsem pri spodnjekrednih temnosivih apneneih in dolomitih ter pri Ko- menskem in Tomajskem apneneu eenomanijske do senonijske starosti. Zato smo iz krednega zaporedja geokemično raziskali skupaj 102 vzorca apnenca in dolomita (sl. 2). Polovica raziskanih vzorcev krednih apnencev in dolomitov je spodnjekredne sta- rosti. Odvzeli smo jih na 20 lokalitetah. Hauterivijske starosti sta okrog 15 metrov debeli paket temnega ploščastega apnenca na Sabotinu in 40 metrov debeli paket črnega ploščastega apnenca z rožen- cem, ki izdanja ob cesti pri cerkvi v vasi Trnovo na Trnovskem gozdu. Po strukturi je apnenec na Sabotinu biomikrit in biopelmikrit; odlagal se je v zaprtem šelfu z lagu- nami. Delež organske snovi v petih raziskanih vzorcih se giblje med 0,15 in 0,87 % s srednjo vrednostjo petih vzorcev 0,36 % C . Več organske snovi vsebuje apnenec pri Snovem. Za štiri raziskane vzorce imamo vrednosti CQj.g med 0,42 in 1,08 %. Pirolitske analize kažejo, da ima ta apnenec genet- ski potencial v mejah od 3,88 do 4,13 mg HC/g kamnine, kar pomeni, da ga uvrščamo med matične kamnine z nizko sposobnostjo generiranja ogljikovodikov. Kerogen je označen kot tip II (mešani sapropelsko-huminski tip) s povečano količino lipidov morskega izvora, zrelost organske snovi, ocenjena na osnovi Tj^^^^ 426 in 427°C pri pi- rolizi pa je nizka. Glede na relativno visoke vrednosti CQj.g smo pri vzorcih iz Trnove- ga pričakovali precej višji genetski potencial. Predvidevamo lahko, da je bil delež ke- rogena zmanjšan pri oksidacijskih procesih, kar je povzročilo zmanjšanje naftne gen- eracijske sposobnosti apnenca. Delež bitumna v dveh raziskanih vzorcih je visok in se giblje med 1770 in 2010 ppm. V njegovi komponentni sestavi prevladujejo asfalteni (40-53 %) nad smolami (18-24 %), delež ogljikovodikov pa je nizek in znaša le 30-36 %. Plinsko-kromatografska analiza je pokazala, da pripada v bitumnu 92 % n-alka- nom, izoalkanov pa je 7 %. Razen algnih lipidov sestavljajo organsko snov tudi mi- kroorganizmi (bakterije). Razmerje pristana in fitana (Pr/Ph) je nižje od 1 (0,35 in 0,52), kar kaže na anoksične razmere med sedimentacijo apnenca. Raziskani bitumen je sekundarnega izvora, v začetnem zrelem stadiju spremembe, njegova komponentna sestava pa kaže neke degradacijske značilnosti, kar je razumljivo glede na površinske vzorce. Barremijsko-aptijske starosti je pet vzorcev iz okrog 10 metrov debelega paketa temnih dolomitiziranih apnencev z lističasto krojitvijo pri Voglarjih na Trnovskem gozdu in osem vzorcev iz okrog 25 metrov debelega zaporedja ploščastega črnega bio- mikritnega apnenca s tankimi polami laporja na Sabotinu. Vzorci iz Voglarjev vsebu- jejo 0,29 do 0,54 % CQj.g, ki je terestričnega izvora (ligninsko-huminski detritus z vključki vitrinita). Za vzorce s Sabotina, ki vsebujejo- 0,61 do 0,85 % C , je značilen zelo nizek naftni potencial. Ta je pogojen z neugodnim, terigenim poreklom organske snevi. Ogljikovi indeksi raziskanih vzorcev so v mejah 171-246 mg HC/g CQj.g in kažejo, da je apnenec dosegel zrelo katagenetsko fazo organske spremembe. Apnenec vrhnjega dela barremijsko-albijskega zaporedja smo raziskali z dvema profiloma pri Markovščini in Golcu pri Obrovu. Osem vzorcev temnega in ponekod ploščastega biomikritnega apnenca vsebuje 0,42 do 0,56 % organske snovi. Bitumen iz profila pri Marko vščini je bil raziskan tudi s komponentno in kromatografsko Potencialnost karbonatnih kamnin za nastanek ogljikovodikov v zahodni Sloveniji_2^7 analizo. Ekstrakt bitumna kaže povečano vsebnost smolnih (43 %) in asfaltenskih (22 %) komponent. Plinsko-kromatografska analiza je pokazala povečani delež n- alkanov (66 %) in dominacijo ogljikovodikov v molekularnem območju C^g-Cgg. Pri- sotni bitumen je sekundarnega, migracijskega porekla, komponentna sestava pa kaže na njegovo kasnejšo spremembo. Temni apnenci, dolomiti in dolomitne breče albijsko-cenomanijske starosti ses- tavljajo na Tržaško-komenski planoti več sto metrov debelo Povirsko formacijo (Jur- kovšek et al., 1996). Iz spodnjega dela formacije smo pri Povirju raziskali sivi zrnati dolomit, ki ima duh po bitumnu, dva vzorca pa sta iz temno sivega miliolidnega apnenca Povirske formacije. Dolomit je nastal s kasnodiagenetsko dolomitizacijo in vsebuje 0,17 do 0,76 % CQj.g. Organska snov je koncentrirana v medzrnskih porah in domnevamo, da je produkt migracije ogljikovodikov med kasnejšo diageneze. Apne- nec iz istega paketa, odvzet pri Divači, ima občutno manj organske snovi (0,08 in 0,28 %). Raziskave temno sivega in črnega laminiranega in stromatolitnega apnenca in ploščastega miliolidnega apnenca, odvzetega ob železniški progi pred predorom med Dutovljami in Vrhovljami, je z organsko snovjo bogatejši. Osem raziskanih vzorcev iz te lokalitete vsebuje med 0,35 in 0,78% C , kar je glede vsebnosti organskih snovi na spodnji meji matičnosti za karbonate. Tudi v teh plasteh je neugodna sestava kero- gena, saj prevladuje kerogen terestričnega izvora (tip III) z zelo nizkim genetskim potencialom (0,62 mg HC/g kamnine). V zgornjem cenomaniju in turoniju se je na Dinarski karbonatni plošči zahodne Slovenije odlagal večidel debeloplastoviti do masivni rudistni apnenec (rudistne lupine so premeščene), na Tržaško-komenski planoti znan kot Repenska formacija (Jurkovšek et al., 1996). Rudistni apnenec lokalno nadomešča sivi plastoviti in mikritni apnenec s pelagičnimi fosili, ki kažejo na vpliv cenomanijsko-turonijske pelagične epizode. Pet vzorcev, odvzetih severno od Sežane, kaže, da ta mikritni apnenec nima nobenega naftnega potenciala, saj vsebuje le 0,02 do 0,15% organske snovi. Z evstatičnim dvigom morske gladine v cenomaniju in turoniju (Haq et al., 1987) je prišlo ponekod na Dinarski karbonatni platformi do nastanka lagun z anoksičnimi razmerami, v katerih so se odlagali čmi ploščasti in laminirani apnenci z rožencem, ki so v literaturi poznani kot Komenski apnenci, komenski skrilavec ali celo ribji skrilavec (Buser, 1973; Ogorelec et al., 1987; Jurkovšek et al., 1996; Šribar, 1995). Marsikje na Krasu te plasti vsebujejo dobro ohranjene karbonizirane ribje skelete in številne fosile pelagičnih organizmov. V zadnjem času pogosto omenjajo prav cenomanijsko-turonijski nivo Komenskega apnenca med dokazi za drugi ocean- ski anoksični dogodek (Jenkyns, 1991; Jurkovšek et al., 1996; Ogorelec et al., 1996; Kolar-Jurkovšek et al., 1996). Zato smo se ugodnih naftno-geoloških rezulatov o organski snovi v karbonatnih kamninah na Krasu nadejali prav pri temno sivih ploščastih in laminiranih apnencih z gomolji roženca. Večidel, okrog 100 metrov debeli paket Komenskega apnenca je razvit v okolici Komna, manjše oziroma tanjše leče podobnega apnenca pa se na južnem delu Tržaško-komenske planote pojavljajo še v spodnjem senoniju (sl. 2), vendar slednjih ne moremo povezati s prej omenjenimi dogodki. Kljub ugodnemu faciesu in drugim litološkim parametrom pa vsebuje Komenski apnenec iz različnih nivojev relativno malo organske snovi. V desetih preiskanih vzorcih se delež giblje med 0,38 in 0,83 %; le v enem vzorcu dosega vsebnost CQj.g 1,74%, kar sicer nakazuje srednje dobro matičnost. Optične raziskave kažejo, da v 228_B. Ogorelec, B. Jurkovšek, D. Šatara, G. Barič, B. Jelen & B. Kapovid apnencu prevladuje organska snov terestričnega izvora (ligninsko-huminski tip), kar kamnini precej znižuje njeno sposobnost za nastanek ogljikovodikov. Podobne organsko-kemične parametre, kakor jih ima Komenski apnenec, kaže tudi črni ploščasti apnenec z rožencem, ki je santonijsko-campanijske starosti in se javlja znotraj Lipiške formacije (sl. 2). Poimenovan je kot Tomajski apnenec (Jur- kovšek et al., 1996) in izdanja v več tanjših horizontih in lečah na jugovzhodnem delu Tržaško-komenske planote. Raziskali smo ga v železniškem useku pri Dutovljah. Šest raziskanih vzorcev vsebuje 0,32 do 0,73% s srednjo vrednostjo 0,48 %, kar Tomajski apnenec uvršča na spodnjo mejo naftne potencialnosti. V primerjavi s Ko- menskim apnencem vsebujejo raziskani vzorci Tomaj skega apnenca več organske snovi vodnega porekla (alginita), kar je za naftno matičnost kamnine vsekakor ugod- nejše. Apnenec spodnjesenonijske starosti (coniacij-santonij) pripada plastovitemu sive- mu biomikritnemu apnencu z redkimi rudistnimi biostromami (Sežanska formacija - Jurkovšek et al., 1996). Lokalno se v tem apnencu pojavljajo vrhnji vložki oziroma paketi črnega Komenskega apnenca, opisanega prej. S 14 vzorci smo apnenec Sežan- ske formacije raziskali v profilih okrog Sežane in pri Divači. Raziskani vzorci kažejo zanemarljivo vsebnost organske snovi, kar jih ne uvršča v potencialne matične kamnine za nafto in plin. Njihov delež CQj.g se giblje med 0,04 in 0,29%. Optične analize kerogena kažejo, da je organska snov terestičnega izvora. Prehodne plasti na meji kreda/paleocen Prehodne plasti med zgornjo kredo in paleocenom, imenovane tudi Libumijska formacija (Stäche, 1889; Pavlove c, 1963; Jurkovšek et al., 1996), smo raziskali orientacijsko s profili pri Vremskem Britofu, Kozini, Štorjah in Senadolah. Debelina te formacije je na prostoru Tržaško-komenske planote zelo spremenljiva in doseže debelino med 100 in 400 metri. V spodnjem delu formacije, ki je še maastrichtijske starosti, se menjavajo temni biomikritni apnenci s plastmi svetlejšega biosparita z giroplevrami. Večidel Liburnijske formacije pa gradi temnosiv do črn, večkrat neko- liko lapomat biomikritni apnenec. Ta se je odlagal na plitvem zaprtem šelfu in v lagunah. Emerzijske breče, izsušitvene pore in stromatolitne plasti, ki so najpogost- nejše prav na meji med kredo in tereiarjem, kažejo na občasne litoralne razmere in cementacijo v vadoznem okolju. Pogostne so tudi inkrustacije karbonatnega sedimen- ta s Paroniporo sp. v vadoznem okolju (Drobne et al., 1988; Jurkovšek et al., 1996; Ogorelec et al., 1995). Med favno prevladujejo miliolide, haraceje, laginofore ter skeletne in neskeletne alge. Vsebnost organske snovi v 25 raziskanih vzorcih iz Liburnijske formacije je nižja od spodnje meje za matičnost kamnine. Delež CQj.g se giblje med 0,02 in 0,43 % s po- prečjem 0,23 % CQj,g. Izjema je le vzorec karbonatnega laminila tik pod plastjo z rapi- dioninami v Vremskem Britofu, ki vsebuje 0,74% C . Kljub povišani vsebnosti organske snovi v tem vzorcu pa je pirolitska analiza pokazala, da laminit nima spo- sobnosti za generiranje ogljikovodikov. Vsebnost termovaporiziranega ogljikovodika je nizka in kaže na skromno vsebnost bitumna (205 ppm). Mikroskopska analiza kerogena kaže, da tega v enaki meri sestavljata terestrična in amorfna snov, medtem ko je liptinidne komponente le okrog 5 %. Liptinidi kažejo jasno rumeno fluorescen- co, medtem ko amorfna komponenta zelo slabo ali celo ne fluorescira. Na podlagi teh analiz lahko sklenemo, da je amorfna snov alohtonega izvora oziroma je rezultat Potencialnost karbonatnih kamnin za nastanek ogljikovodikov v zahodni Sloveniji_2^7 spremembe terestrične organske snovi. Na pretežno terestrični izvor organske snovi v apnencih Liburnijske formacije nam kažejo tudi tanjše plasti premoga, ki se pojavlja- jo pri Vremskem Britofu, Lipici, Rodiku in Sečovljah. Razprava in sklepi Raziskave so zajele blizu dvesto vzorcev različnih apnencev, dolomitov in karbon- atnih skrilavcev iz zahodne Slovenije. Stratigrafsko je zastopano celotno zaporedje od zgornjega perma prek posameznih triasnih formacij do jurskih in krednih plasti. Težišče raziskanega ozemlja je bilo Slovensko Primorje, kjer smo analizirali karbon- ate šelfnega razvoja, manjši del raziskav pa je zajel tudi globljevodne sedimente Slovenskega jarka. Te smo raziskovali v širši okolici Cerknega. Dobljeni rezultati o naftni potencialnosti raziskanih kamnin so, kar moramo pou- dariti, še vedno zelo orientacijski, saj je bil naš namen v tej fazi le, da analiziramo čimveč potencialnih formacij za generiranje ogljikovodikov. V ta namen smo zazdaj raziskali 14 formacij. Podatki predstavljajo le manjši korak naprej glede na dosedan- je poznavanje tovrstne problematike. Zavedati se moramo, da vse navidez bituminoz- ne kamnine niso matične za nafto in plin. Ugotavljanje naftne potencialnosti kamnin je namreč zelo kompleksno, odvisno od številnih geokemičnih in drugih sedimento- loških parametrov. Osnovna pogoja za nastanek nafte sta predvsem pravi facies kam- nine in stopnja zrelosti organske snovi, iz katere se ob ugodnih fizikalno-kemičnih razmerah ta lahko generira, migrira in akumulira v razne pasti. Podrobnejši podatki oziroma rezultati organsko-kemičnih, mikroskopskih in faci- alnih analiz so podani za vsako geološko obdobje in formacijo že med tekstom. Zato tu prikazujemo le osnovne sklepe: - Zgornjepermski apnenec in dolomit šelfnega razvoja idrijskega prostora (Ža- žarska formacija) sta bila raziskana s 35 vzorci. Kljub temni barvi je vsebnost C^^.^ v njih dokaj skromna (0,08 do 0,62 %), kemične in optične analize bitumna pa kažejo, da ima organska snov pretežno terestrični izvor in visoko termično spremembo (R^ = 2,3 %), ki predstavja že začetno fazo metageneze. - Triasne plasti so bile raziskane z 51 vzorci. V povprečju vsebujejo okrog 0,2 % Cq . Izjemi sta le črni ladinijski apnenec iz okolice Jagrš (0,2 do 2,7 % Cpj.g, poprečno 1,2%) in karnijske plasti (jul in tuval) iz okolice Drenovega griča in Trebuše (0,14 do 2,51 % Cqj.^, poprečno 0,35 %). Vsi ti apnenci imajo tudi neugodno sestavo organske snovi, saj imajo skromen delež bitumna (pod 200 ppm), organska snov pa je tudi tu pretežno terestričnega izvora. Zato triasni karbonati zazdaj za naftno potencialnost niso posebno zanimivi. - Glede na to, da se je jurski apnenec odlagal na dobro prezračeni, plitvi Dinars- ki karbonatni plošči, le-tega že po faciesu nismo predvideli kot potencialnega za ogljikovodike. Zato ga tudi nismo raziskali s kemičnimi in optičnimi metodami. Iz spodnjejurskega odbdobja smo raziskali le 8 vzorcev črnega apnenca in karbonatnega skrilavca iz Slovenskega jarka. Rezultati so skromni (0,3 do 0,48 % CQj.g in nizek delež bitumna - pod 200 ppm). - Največjo pozornost pri raziskavah smo namenili spodnjekrednim temnim apnencem in dolomitom ter zgornjekrednima Komenskemu in Tomajskemu apnencu na Tržaško-komenski planoti. Kredne plasti smo raziskali z 92 vzorci. Kot delno potencialno matično kamnino smo zazdaj izdvojili črni ploščasti apnenec hauterivij- ske starosti iz Trnovega pri Novi Gorici, ki ima 0,42 do 1,08 % CQj.g in genetski naftni 230_B. Ogorelec, B. Jurkovšek, D. Šatara, G. Barič, B. Jelen & B. Kapovid potencial 3,88 do 4,13 mg HC/g kamnine. Organsko snov v pretežni meri sestavlja alginit. - Manj obetavni so zazdaj rezultati analize organske snovi Komenskega in Tomajskega apnenca. Kljub temu, da oba kažeta ugoden facies (črni karbonatni lami- niti lagunskega razvoja) in nad 0,5 % CQj.g v povprečju, pa je v njih neugodna sestava organske snovi, saj prevladuje terestrična komponenta. Tomajski apnenec vsebuje v primerjavi s Komenskim apnencem vseeno nekoliko več alginita, kar je za naftno potencialnost ugodnejše. - Apnenec Liburnijske formacije na prehodu zgornje krede in paleocena smo raziskali s 25 vzorci. Kljub navidez ugodnemu faciesu kamnine in njegovi temni barvi je vsebnost organske snovi v apnencu zelo nizka (povprečno 0,23 % CQj.g), skromna pa je tudi vsebnost bitumna (pod 200 ppm). Kerogen v enaki meri sestavljata terestrična in amorfna snov. Matičnost karbonatnih kamnin zahodne Slovenije je podoben geološki problem, kakršnega srečujemo na severozahodnem delu Jadransko-dinarske karbonatne plat- forme, saj je bila jugozahodna Slovenija v celotnem mezozojskem obdobju njen ses- tavni del. S to poblematiko so se na območju Dinaridov intenzivno ukvarjali že Ogulinec (1952), Gjetvaj in sodelavci (1986), Koščec (1972), Grandie (1974), kasneje pa Šebečič (1979, 1980, 1982, 1984, 1988), Šebečič in Ercegovac (1983), Baričeva (1971, 1988), Baričeva in sodelavci (1987, 1991), Cota in Baričeva (1997) in drugi. Med potencialne matične kamnine se v Dinaridih najpogosteje, glede na facies, uvrščajo zgornjekredni oziroma turonij ski laminirani apnenci (Jelaska, 1973; Jer i- nič et al., 1974), zgomjepermski lagunski apnenci in drobnozrnati apnenci šelfnih korit (lemeški razvoj - Grandie, 1974), glede na kemične analize organske snovi pa zgornjekredni apnenci (raziskovalna vrtina na Braču - Jacob et al., 1983) in pale- ogenski apnenci (raziskave pri Sinju). Gjetvaj in sodelavci (1986) iščejo matične kamnine glede na tektoniko in debelino evaporitnega kompleksa v večjih globinah, in sicer v karbonskih, permskih, srednje- in zgornjetriasnih, zgornjejurskih in zgorn- jekrednih plasteh. Šebečič (1988) je precej skeptičen za generiranje in akumulacijo nafte v Zunanjih Dinaridih. To utemeljuje s tankimi paketi kerogenih sedimentov mezozojske starosti, ki ne predstavljajo posebno velik naftni potencial, in z debelimi evaporitnimi kompleksi, ki so v povprečju debeli od enega do dva tisoč metrov, največ pa do 3.800 metrov (vrtina Nin-1; Kranjec, 1981). Generiranje nafte v Dinaridih je po Šebečiču (1988) poseben problem tudi zaradi nizkih geotermičnih gradientov v karbonatnih formacijah, kjer ti znašajo le 1-1.7°C/100 m (Horvat et al., 1987). Zato naj bi bile matične kamnine zelo globoko, problem pa naj bi bile tudi večje akumu- lacije kerogena tipa I in II. Pojavi matičnih kamnin so ugotovljeni na raznih delih Jadranske karbonatne platforme (Barič, 1971, 1988; Barič et al., 1987, 1991; Cota & Barič, 1977). Kot dobre matične kamnine so izločeni karbonatni paketi spodnje in zgornjekredne staro- sti iz bazena Dugega otoka. Organska snov je v teh kamninah pretežno morskega iz- vora in je v nezrelem do zrelem stadiju termičnih sprememb. V nekaterih vrtinah ka- žejo znake matičnih kamnin za nastanek ogljikovodikov tudi jurski in triasni sedi- menti, čeprav imajo te kamnine zaradi svoje litološke heterogenosti zmanjšan naftni potencial. V zadnjem obdobju se naftno-geološke raziskave Dinarsko-Jadranskega prostora intenzivirajo, predvsem z dodatnimi seizmičnimi meritvami, laboratorijski- mi analizami in reinterpretacijami starejših podatkov. Za slovenski prostor so pomembni podatki globoke vrtine Ro-1 pri Rovinju. Zanjo Potencialnost karbonatnih kamnin za nastanek ogljikovodikov v zahodni Sloveniji_2^7 je značilno, da je brez sledov ogljikovodikov, čeprav ima ugodno lego na temenu antiklinale istrskega paraavtohtona in je brez evaporitov (Kranjec, 1981). Razen Jadransko-Dinarske karbonatne plošče so zaradi primerjav slovenskega prostora zanimive tudi naftno-geološke ugotovitve prostora severne Italije (Matta- velli & Novelli, 1990; Pieri & Mattavelli, 1986; Dainelli & Pieri, 1986). Kot matične kamnine za nafto in plin omenjeni navajajo avtorji zgornjepermski Belerofonski apnenec, predvsem pa retijsko-liasne karbonatne skrilavce Južnih Alp, ki so se odlagali v prostranih evksinskih bazenih (formacija Riva di Solto) in laporne apnence na meji spodnje in zgornje krede. Evksinski bazeni so iz obdobja retija znani tudi iz formacije Glavnega dolomita v Severnih Alpah (Zanki, 1971; Fruth & Scherreiks, 1984). Nafta naj bi po termalni zrelosti nato migrirala v sosednje me- zozojske karbonatne kolektorje, vlažni plin in kondenzati pa so v Padski nižini migri- rali v terciarne klastične kolektorje (Mattavelli et al., 1983). V vzhodnem delu Padske nižine je na globini pod 3000 metri produktivno naftno polje Gavone, kjer so kolektorske kamnine spodnjekredne apnenčeve in dolomitne breče, kakršne poznamo pri nas na Krasu znotraj Brske in Povirske formacije (Jurkovšek et al., 1996). Če se po kratki razpravi in primerjavi nekaterih naftno-geoloških podatkov iz Jadransko-Dinarske karbonatne plošče ter bližnjega prostora severne Italije in Južnih Alp vrnemo v slovenski prostor, lahko štejemo med delno potencialne matične kamnine za nastanek ogljikovodikov v zahodni Sloveniji le tanjše pakete spodnje- krednega temnega apnenca. Precej manj so zazdaj ugodni podatki zgornjepermskih in zgornjekrednih apnencev in dolomitov, medtem ko so jurske in triasne karbonatne kamnine raziskanega prostora za nafto nezanimive. Zahvala Avtorji se za strokovno recenzijo in koristne nasvete k tej razpravi prisrčno zah- valjujemo akad. prof. dr Mariu Pleničarju in uredniku revije prof. dr Stanku Buserju. Finančno sta raziskave omogočila Nafta Lendava in Ministrstvo za znanost in tehno- logijo Republike Slovenije prek raziskovalnih projektov. Vsem naša iskrena hvala. 232_B. Ogorelec, B. Jurkovšek, D. Šatara, G. Barič, B. Jelen & B. Kapovid Carbonate rocks of west Slovenia as potential sources for hydrocarbons Introduction During the past few decades, the oil and gas exploration in Slovenia has been focused on the Neogene strata in the Mura depression located in western part of the Pannonian basin. In this area some minor oil and gas fields were found. Geological exploration of the Slovenian part of the Dinarides was much slower mainly due to several km thick complex of the Jurassic and Cretaceous beds. Since untili present almost no data on organic matter contents in carbonate rocks were available and their potential as source rocks was fairly unknown, a research pro- gramme based on a team of Slovenian and Croatian geologists was formed. For the research purposes about 200 samples of limestones, dolomites and shales of different ages ranging from the Upper Permian to Paleogene were investigated. The studied strata are located in the SW part of Slovenia (fig. 1). According to facies, colour and other lithologie characteristics of potential rocks the Upper Permian limestone and dolomite, Carnian beds and Cretaceous laminated and platy dark colored limestone from the Triest-Komen plateau (figs. 1 and 2) have been chosen for studies. All studied samples were investigated by the bituminous luminiscence and the C contents was determined. On 38 chosen samples the pyroly- sis of organic matter and composition of bitumen have been performed as well the optical analysis of kerogen. Results The Upper Permian limestones and dolomites have been studied on 35 samples from the Idrija and Žiri region (fig. 1). Their depositional environment was restricted shelf of lagoonal character. The dolomite is mainly of early diagenetic origin (Grad & Ogorelec, 1980; Bus er et al., 1986). The analyses indicate that the C^^^ content is relatively low in spite of their dark color and local bituminous odour. The majority of samples contain from 0.08 to 0.62 % of CQj.g and up to 870 ppm of bituminous mat- ter. Optical analysis of kerogen indicates strong predominance of macérais of the vit- rinite group. The distribution of Cj^^-Cg^ hydrocarbons with strong predominance of C24 indicates terrestrial origin of organic matter. Due to low CQj.g content and kerogen composition, the Upper Permian rocks are not considered potential source rocks for hydrocarbons. Scythian beds are developed in part clastically and in part as carbonates on the territory of Slovenia. In the uppermost part of the sequence an up to 60 m thick pack- age of dark coloured limestone of lagoonal facies occurs. Three samples of the men- tioned limestone were analysed; the C contents were up to 0.11 %. Anisian beds were investigated with 6 samples from the profile Babe at Cerkno. The beds are developed as bedded dolomite of lagoonal and intertidal environment. Locally, the dolomite is replaced by a dark biomicritic limestone. The studied samples contain from 0.08-0.30% of and therefore can not be regarded as potential source rocks for hydrocarbons. Ladinian beds are diversely developed in west Slovenia due to collapse of the Slovenian platform and the formation of two separated carbonate platforms - Dinar- Carbonate rocks of west Slovenia as potential sources for hydrocarbons_233 ic and Julian, and the Slovenian trough located in-between (B u s e r, 1989). Carbonate rocks encountered in the trough are accompanied by shales and extrusive rocks. From the Idria area, 12 samples of dark platy limestone were analysed. According to their structure they belong to micrites with pelagic fauna. The organic matter con- tents of the investigated samples range from 0.10 to 2.76 % and the average value is of about 1.2 % CQj.g. In spite of favourable C data, the pyrolysis analyses (high S3 val- ues) and the composition of macérais (high percentage of the vitrinite matter) the kerogen is of unfavourable composition. The organic matter is only a remain of ter- restrial components the limestone was enriched with during sedimentation processes. Carnian beds were deposited on a carbonate platform as well as in deeper environ- ment of the Slovenian trough. From Drenov grič and surroundings of Trebuša (figs. 1 and 2) 19 samples of dark biomicritic limestone of lagoonal fades were studied. The Cpj.g contents of these samples range from 0.14 to 2.51 %, being 0.35 % in average. The limestone is low in soluble bituminous matter (up to 200 ppm), and the organic matter is mainly of terrestrial origin. Very high reflection index (Ro = 2.2 -3.2 %) indicates the attained degree of metagenesis. In somewhat deeper environment of the Slovenian trough dark limestones and shales (Amphyelina beds) were deposited during the Carnian time. Five investigated samples of this fades type contain 0.07 to 0.32 % of C , which makes it too low for the limestone to be regarded as potential rock for the hydrocarbons. Norian-Rhaetian beds of west Slovenia are developed as the Main dolomite and its lateral equivalent the Dachstein limestone, and on the territory of the Slovenian trough as coarse grained Bača dolomite with chert lenses. All above mentioned forma- tions are not very promissing for oil exploration due to their light colour and lithology. We have analysed only four samples of the darker stromatolitic dolomite formed in the restricted littoral parts of the carbonate platform (Ogorelec & Rothe, 1993). The CQj.g content in the studied samples ranges from 0.06 to 0.61 %, being 0.15 % on the average, which is too low for the rocks to be regarded as potential oil source rocks. During the Jurassic the limestones of the Dinaric platform were deposited on shal- low, mainly open carbonate platform (Buser, 1979; Orehek & Ogorelec, 1980). The Liassic and Dogger successions are characterised by several hundreds metres thick sequence of oolitic and biosparitic limestone. During the Lower Malm, a huge coral reef developed on the territory of Trnovski gozd (Turnšek, 1966;Turnšek et al., 1981). According to the structural types and facial characteristics, the Jurassic limestones of the Dinaric platform can not be regarded as potential source rocks. For this reason they were not geochemically examined during this stage of studies. As a potential source rock of the Jurassic age black platy limestones and carbona- ceous shales from a 150 metres thick package occurring in the Slovenian trough were analysed. These beds contain between 0.16 and 0.48% of C (8 investigated sam- ples), similarly low is also the content of bitumen (100-200 ррпђ. The most favourable data were expected from Cretaceous limestones and dolomites. For this reason 102 rock samples were analysed. Based on the data obtained, four samples of dark-coloured platy biomicritic lime- stone of Hauterivian age are very promising. The limestone outcrops in a 40 metres thick sequence in Trnovo near Nova Gorica. The C^j.^ content ranges from 0.42 to 1.08% in the treated samples. The pyrolysis study indicates the rock production index ranges from 3.88 to 4.13 mg HC/g rock ranging them among source rocks with low potential for hydrocarbon generation. Kerogen is a mixture of sapropelic-humine type with increased amounts of lipids of marine origin. 234_B. Ogorelec, B. Jurkovšek, D. Šatara, G. Barič, B. Jelen & B. Kapovid The samples of the Barremian - Aptian age from the Komen plateau comprise from 0.29 to 0.78 % of CQj.g, the average being of approx. 0.5 %. According to their structure they belong to dark-colored, commonly platy and locally dolomitised bio- micritic limestones. Their depositional environment w^as restricted shelf of lagoonal character with local and episodical littoral conditions. The samples have unfavourable composition of organic matter as it is chiefly of terrestrial origin with low production index (under 1 mg HC/g rock). The organic matter is concentrated in intercrystalline pore spaces in dolomite of Povirje formation, and we suppose that it is a result of hydrocarbon migration during the late diagenesis. During the Upper Cenomanian and Turonian the majority of thickly bedded to massive rudist limestone was deposited. On the Trieste-Komen plateau, this lime- stone is known as the Repen Formation (Jurkovšek et al., 1996). With eustatic rise of the sea level locally lagoons with anoxic conditions existed on the platform. These lagoons were the depositional environment of black-coloured and laminated lime- stones with chert nodules known in the literature as the Komen limestone (B u s e r, 1973; Ogorelec et al., 1987; Jurkovšek et al., 1996). Beside the benthic fossils numerous pelagic organisms - calcispheres mainly are present indicating episodical interconnections of lagoons with the open sea. They are the only evidence for the sec- ond oceanic anoxic event (OAE II- Jenkyns, 1991). In spite of unfavourable facies and other lithologie characteristics the Komen limestone contains relatively small amounts of organic matter. In 10 of the investigated samples, the contents of C ranges from 0.38 to 0.83%, and only in one of the samples it amounts to 1.74 % of CQj.g. However, the results of optical investigations are unfavourable due to terrestrial origin of organic matter in this limestone. Similar parameters based on organic chemistry and facies as obtained for the Komen limestone are also encountered in the black-coloured and platy Tomaj lime- stone with chert nodules of the Santonian-Campanian age (Jurkovšek et al., 1996). Six of the investigated samples contain from 0.32 to 0.73 % of C , what ranks the Tomaj limestone to the lowermost range of hydrocarbon potential source rocks. In comparison with the Komen limestone it contains more organic matter of marine ori- gin. Transitional beds encountered on the Cretaceous/Tertiary boundary known also as Liburnian formation (Stäche, 1889; P a vi o ve c, 1963; Jurkovšek et al. 1996) were studied in several profiles. On the territory of Karst, the formation attains between 100 and 400 metres of thickness. In the lower part of the formation alterna- tion of dark-coloured biomicritic limestone and light-coloured limestone with gyro- pleuras and rudists is prevailing. The majority of the formation is of Danian age and consists of dark to black marly limestone. It was deposited in a restricted shelf envi- ronment with lagoons. The organic matter contents in 25 studied samples from the Liburnian formation indicates that this limestone is not potential oil source rock. The contents of CQj.g ranges from 0.08 to 0.43 %. Kerogen is composed of equal parts of terrestrial and amorphous matter. The obtained results for the hydrocarbon genetic potential of the investigated Upper Permian and Mesozic carbonate rocks of west Slovenia must still be consid- ered only informationally. The analyses encompassed 14 formations each of them being represented with only few samples collected from the surface. Therefore, the obtained data can serve as guideline for future studies of potential oil and gas source rocks in Slovenia. 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GEOLOGIJA 39, 239-214 (1996), Ljubljana Rezente tektonische Aktivität des Krsko-Einbruchstales (Slowenien) Recentna tektonska aktivnost Krške udorine Uroš Prem.ru Geologische Anstalt Ljubljana Institut für Geologie, Geotechnik und Geophysik Dimičeva ul. 14, SI-1000 Ljubljana, Slowenien Schlüsselworte: rezente Tektonik; vertikale Bodenbewegungen (slip rate), Flusslaufverlegungen; aktive Störungszonen; Korrelation der geologischen, seis- mischen, seismotektonischen, arhäologischen, historischen und geomorphologi- schen Daten; Dauern der letzten neotektonischen Phase Ključne besede: recentna tektonika; hitrosti vertikalnih premikov; spreminjan- je rečnih tokov; aktivne prelomne cone; korelacija geoloških, seizmoloških, seiz- motektonskih, arheoloških, zgodovinskih in geomorfoloških podatkov; trajanje zadnje neotektonske faze Zusammenfassung Die Arbeit umfasst die Korrelation von geologischen, seismologischen, archäologischen und geomorphologischen Daten im Gebiet der rezenten tektoni- schen Aktivität. Als ein Beispiel dafür wurde der Erdbeben-aktive Krško-Ein- bruchstal in Südost-Slowenien genommen. Es werden die morphotektonischen Merkmalen von aktiven Störungen und Beispiele von Flussbett-Verlegungen im Quartär und Holozän, sowie auch in der geschichtlichen Zeit abgehandelt. Die archäologischen Daten über die Katastrophen in dem mittelalterlichen Markt Gutenwerth wurden mit den Daten über die geschichtlichen Erdbeben und den seismischen Wirkungsfähigkeiten kompariert. Es wurden die rezenten vertikalen Bodenbewegungen in verschiedenen Gebieten des Krško-Einbruchstales und aus verschiedenen Zeitabschnitten ausgerechnet. Mit einer Regressionsfunktion wurde die Abhängigkeit der vertikalen Bodenbewegungen von der Zeit bewiesen. Aus der Regressionsfunktion wurden die Schlussfolgerungen über den Anfang der letzten neotektonischen Phase abgeleitet und es wurden die Möglichkeiten für Voraussagen der Dauer und der Höhepunkt-Zeit mit den möglichen grössten Mag- nituden der Erdbeben bei gleichzeitiger Vergrösserung der vertikalen Bodenbewe- gungen. Aus den Daten über die Höhen von Schotterterrassen und den festgestell- -feen vertikalen Bodenbewegungen werden die zeiÜichen Veränderungen des Sava- Flusslaufes wegen der tektonischen Bewegungen in der geschichtlichen Zeit angegeben. Damit aber wird ein quantitativer Beweis abgeleitet, dass für die Flussbett-Verlegungen die tektonischen Bewegungen an den Störungen die Ursache sind. 240_Uroš Premru Kratka vsebina Prispevek obravnava korelacijo geoloških, seizmoloških, arheoloških in geo- morfoloških podatkov pri recentni tektonski aktivnosti. Kot primer je obdelana potresno aktivna Krška udorina v jugovzhodni Sloveniji. Obravnavani so mor- fotektonski kazalci aktivnih prelomov, primeri prestavitve rečnih strug v kvartar- ju in holocenu kakor tudi v zgodovinskem obdobju. Arheološki podatki o katas- trofah v srednjeveškem trgu Gutenwerth so komparirani s podatki o zgodovinskih potresih in o seizmični zmogljivosti. Izračunane so hitrosti recentnih vertikalnih premikov (slip rate) z različnih delov Krške udorine in iz različnih časovnih obdo- bij. Z regresijsko funkcijo je dokazana odvisnost hitrosti vertikalnih premikov od časa. Iz regresijske funkcije so izpeljani sklepi o začetku zadnje neotektonske faze in podane možnosti za napovedovanje njenega trajanja in časa njenega vrha z naj- večjimi možnimi magnitudami potresov ob istočasnem povečanju hitrosti vertikal- nih premikov. Iz podatkov o višinah prodnih teras in o ugotovljenih hitrosti verti- kalnih premikov je prikazano časovno spreminjanje rečnega toka Save zaradi tek- tonskih premikov v zgodovinskem obdobju. S tem pa je izpeljan tudi kvantitativni dokaz, da so vzroki za prestavitve rečne struge tektonski v premikih ob prelomih. Einleitung Bei der Korrelation von geologischen, seismotektonischen, seismologischen und archäologischen Daten in tektonisch aktiven Erdbeben-Gebieten bestehen gewisse Schwierigkeiten. Diese interdisziplinäre Synthesen meiden sowohl die Archäologen als auch die Geologen. Die bisherigen spärlichen Analysen haben gezeigt, dass viele Siedlungen in der geschichtlichen Zeit wegen natürlicher Katastrophen verfallen sind. Die Archäologen erklären die Katastrophen als menschliche Tätigkeiten, die Geologen und Geomorphologen aber untersuchen die geologischen Prozesse, Relief- Veränderungen und die Flussbett-Verlegungen in der geschichtlichen Zeit nicht im solchen Masse, wie es diese interessante Thematik verdient. Besonders wertvoll sind die archäologischen Daten mit einer genaueren Datierung der Kultur-Horizonte. Aber nur für seltene archäologische Fundstellen findet man entsprechende Daten über die Sedimentation oberhalb den Kultur-Schichten, die Sedimentmächtigkeit und andere Daten, aus welchen man auf die tektonischen Geschehnisse in der men- schlichen Geschichte schliessen könnte. Als ein Beispiel für die Synthese von geologischen, seismotektonischen, seismolo- gischen, sowie von geschichtlichen und archäologischen Daten haben wir das neotek- tonische Krško-Einbruchstal in Südost-Slowenien ausgewählt, in welchem zahlre- iche archäologische Fundstellen von der Urgeschichte bis zum Ende des Mittelalters bekannt sind. Gerade einige archäologische Daten aus den Fundstellen ermöglichen uns eine gute Korrelation der geologischen, geomorphologischen und seismologis- chen Daten. Am Beispiel des Krško-Einbruchstales ist es möglich eine Korrelation zu zeigen, welche auch mit Ausrechnungen gestützt ist. Kurzbeschreibung des geologischen Aufbaues und der Tektogenese des Krško-Einbruchstales Nach den bisherigen Daten wird die Entstehung des Krško-Einbruchstales in das obere Pliozän gestellt. Der Krško-Einbruchstal ist eine echte intramontane Senkung, welche in mehreren neotektonischen Phasen an der Berührung der Südalpen, der Dinariden und des Pannonischen Beckens in der Zone des mesozoischen Bündels der Rezente tektonische Aktivität des Krško-Einbruchstales (Slowenien) 241 Zagreb-Transform-Störung und zu der paralleler Störungen ausgebildet wurde. Die Gerstaltung des Krško-Einbruchstales ist noch nicht beendet, worauf die rezenten tektonischen Prozesse hinweisen. Der Krško-Einbruchstal ist von plioquartären und holozänen See-, Moor- und Fluss-Sedimenten gefüllt. Die Grundlage dieser Sedimente bilden die Tertiär- Schichten, welche am Rand der Senkung zutage treten (Abb. 1). Die tertiäre Sedi- mentation hatte mit dem Helvet-Konglomerat, -Sand und -Ton angefangen und wurde mit dem tortonischen Konglomerat, Lithotamnien- und Mergelkalk, dem Mergelsandstein und dem Mergel fortgesetzt. Die Sarmat-Schichten bestehen aus Tonmergel, Mergelkalk, Sandstein und Schotter Die Meot-Schichten bestehen aus Kalkmergel und untergeordnet aus Sand, Sandstein, Schotter und Konglomerat. Die Unterpliozän-Schichte bestehen aus Mergel, Ton, Alevrith, untergeordnet aus Sand und Konglomerat. Die Helvet- und Torton-Schichten sind in einem Flachmeer ent- Abb. 1. Geologische Skizze des Krško-Einbruchstales 1- Alluvium allgemein (Holozän); 2- Schotter (Holozän); 3- Schwemmkegel von Šentjernej (Holozän); 4- Quartär-Tone (Würm); 5- plioquartäre Sedimente; 6- Miozän-Sedimente; 7- mesozoische Schichten; 8- neotektonische Störung; 9- neotektonische Störung mit abgesenktem Flügel Sl. 1. Geološka skica Krške udorine 1- aluvij v splošnem (holocen); 2- prod (holocen); 3- šentjemejski vršaj (holocen); 4- kvartarne gline (würm); 5- pliokvartarni sedimenti; 6- miocenski sedimenti; 7- mezozojske plasti; 8- neotektonski prelom; 9- neotektonski prelom s spuščenim krilom 242_Uroš Premru standen, die Sarmat-, Meot- und Unterpliozän-Schichten aber wurden in einem brackischen Becken abgelagert. Die beschriebenen Schichten bilden die Krsko-Syn- klinale mit der Achsenrichtung SW-NO, welche nordöstlich von der Linie Krško- Brežice verhältnismässig gut erhalten ist, südwestlich davon aber von den neotek- tonischen Störungen schon deformiert ist (Šikić et al., 1972, 1978; Pleničar et al., 1976; Pleničar & Premru, 1977). Die Bildung des Krško-Einbruchstales hatte mit dem neotektonischen Störungssystem W-O im oberen Pliozän angefangen. Das Gebiet wurde stufenförmig zu einem Graben abgesenkt, in welchem Tone mit Gehängeschutt und Geröllen von unlöslichen nichtkarbonatischen Gesteinen, überwiegend Hornstein aus den Trias- und Kreide-Schichten, abgelagert wurden. Auf der Anhöhe Gornji Gaj hatte A. Šercelj in dem Ton die Pollen aus dem ältesten Pleistozän bestimmt, welche wahrscheinlich noch in das Oberpliozän reichen (Pleničar & Premru, 1977). In dem Ton und Lehm findet man Zwischenlagen von marmorierten Tonen und sandi- gen Tonen, welche einen festländischen unkarbonatischen Löss mit einen Ursprung aus der Pannonischen Ebene vorstellen. Zwischen den tonigen Sedimenten werden Tone und Lehme gefunden, die gut abgerundete Gerölle enthalten, welche die Paläoströme von Flüssen markieren. Meistens verlaufen die Ströme rechtwinklig vom Rand zum Grund des tektonischen Grabens. Ebenso im Oberen Pliozän folgte, in Form eines stufigen Horstes, an dem Störungssystem NO-SW die Hebung des Gorjanci-Gebirges südlich von dem Krško- Einbruchstal. Es folgte die Erosion von Gorjanci und die Sedimentation des tonigen und klastischen Materials in den Krško-Einbruchstal. Am Ende des Günz-Glazials und im Günz-Mindel-Interglazial wurde an den N0- SW-Störungen ein tektonischer Graben im südwestlichen Teil des Krško-Einbruchs- tales stufenförmig abgesenkt. Die tonigen Schichten wurden umsedimentiert. In dem Mindel-Riss-Interglazial und danach noch im Riss-Würm-Interglazial wurde das W-O-Störungssystem wieder aktiviert, wobei der Krško-Einbruchstal wieder stufen- förmig zu einem tektonischen Graben abgesenkt wurde. In den umsedimentierten tonigen Sedimenten hatte Šercelj (1970) beim Dorf Podbočje einen Pollen-Inhalt aus dem Riss-Würm-Interglazial festgestellt. In den älteren tonigen Sedimenten beim Dorf Zalog westlich von Novo mesto, unter einer sandigen Schicht, zementiert mit Limonit, aber wurden Knochen eines Nashornes Dicerorhinus und Pollen aus dem Riss-Würm-Interglazial gefunden. Es folgte ein tektonisch relativ ruhiger Zeitabschnitt in dem älteren Würm, welcher auch von der Limonitschicht bei Zalog angezeigt ist. Mit dem Interstadial Würm II/III hatte der letzte tektonische Zeitabschnitt ange- fangen (Premru, 1990a, b), in welchen die Störungen verschiedener Richtungen, überwiegend mit Senkungen und weniger mit Hebungen von tektonischen Blöcken, reaktiviert und neu entstanden sind. Ein Netz von aktiven Oberflächen-Störungen, welche aktive Störungszonen bilden, ist entstanden. Das Relief wurde wiederholt umgestaltet. In dem Nordostteil des Einbruchstales wurde, wahrscheinlich im Würm, der Sava-Schotter abgelagert, welcher heute in den Resten der höchsten Schotterter- rasse mit Konglomerateinlagerungen erhalten ist. Der Schotter und das Konglomerat sind überwiegend aus Karbonatgeröllen zusammengesetzt. In dem Mittelteil des Ein- bruchstales wurden tonige Moor-Sedimente mit einer eolischen Komponente abge- lagert. In den tonigen Sedimenten von Krakovski gozd hatte Šercelj (nicht veröf- fentlichte Daten) eine Pollen-Gesellschaft bestimmt, welche auf das Riss-Würm- Interglazial oder wahrscheinlicher auf das jüngste Würm-Interstadial deutet. Rezente tektonische Aktivität des Krško-Einbruchstales (Slowenien)_245 Im Holozän hatte der Sava-Fluss den grössten Teil der Würm-Schotterablagerun- gen erodiert und neue abgelagert. Der Krka-Fluss, dessen ursprünglicher Strom von den Schotterablagerungen in dem tektonischen Graben zwischen den Dörfern Malo Mraševo und Drnovo markiert ist, hatte wegen der tektonischen Verschiebungen im Südteil des Einbruchstales ein epigenetisches Flussbett eingeschnitten, in dem der Fluss noch heute fliesst (Premru, 1976, 1990b; Pleničar &Premru, 1977). Die Umgestaltung des Reliefs wurde in der geschichtlichen Zeit fortgesetzt. Darüber sprechen uns mittelbar die archäologischen und geschichtlichen Quellen, die alten Landkarten und eine alte Graphik, sowie die frischen morphotektonischen Merkmale der aktiven Oberflächen-Störungen und -Klüften, welche mit den seismotektoni- schen und archäologischen Daten kompariert werden können und derer gegenseitiger Zusammenhang mit Ausrechnungen bewiesen werden kann. Erdbeben-Herkünfte (seismic sources) Die Herkünfte der Erdbeben haben wir als aktive Tiefstörungen definiert, deren geographische Position und seismische Wirkungsfähigkeit nach der Methode bes- timmt wurde, welche schon publiziert ist (Premru, 1990 a). Im Gebiet des mittelalterlichen Marktes Gutenwerth (slowenisch = Otok) befinden sich die aktiven Tiefstörungen nördlich von dem Markt (Abb. 3). Die aktiven Tief- störungen haben eine seismische Wirkungsfähigkeit (seismic capability) M^^ von 4,8 (+0,4, -0,0) bis 5,6 (+0,1, -0,2) nach Richter Die grösste seismische Wirkungsfähigkeit des Gebietes beträgt also М^, =5,7. Bei Gutenwerth befindet sich ein Segment der Störungszone, welche in der Richtung WSW-NON von Novo mesto am nordwest- lichen Rand des Krško-Einbruchstales zum Orlica-Berg verläuft (Abb. 2). Im Gebiet des oberen Laufes der Bächer Pendirjevka und Bell potok in dem Gor- janci-Gebirge befinden sich in der Tiefe aktive Störungen mit einer seismischen Wirkungsfähigkeit M^^p von 4,8 bis 5,6. Das erwähnte Störungssegment gehört zu der Störungszone, welche von dem epigenetischen Bett des Krka-Flusses in der Richtung gegen SW nach Gorjanci verläuft (Abb. 2). Im Gebiet des Drnovo-Dorfes befindet sich ein System von Tiefstörungen mit einer seismischen Wirkungsfähigkeit von 5,0 bis 6,2; zwei von den Störungen haben die seismische Wirkungsfähigkeit M^^p=6,0±0,2. Die Tiefstörungen sind auf der Ober- fläche von einem Netz der Oberflächenstörungen begleitet. Sie bilden zusammen eine Störungszone in der Richtung W-0 in dem Nordteil des Krško-Einbruchstales. Nord- westlich von Drnovo schneidet sich die erwähnte Störungszone mit einer NW-SO- Störungszone (Abb. 2). Unter dem heutigen epigenetischen Bett des Krka-Flusses befindet sich eine Tief- störung mit der seismischen Wirkungsfähigkeit M^gp=6,0±0,l, welche dem Netz von Tief- und Oberflächen-Störungen auf der Südseite des Krško-Einbruchstales zuge- hört. Die Störungszone verläuft gegen Osten bis nach Brežice, wo in der Tiefe wieder eine Störung mit einer Wirkungsfähigkeit Mj.3p=6,0±0,l erscheint. In der Störungs- zone befinden sich auch Störungen mit Wirkungsfähigkeiten von 5,0 bis 5,9 (Abb. 2). Die erwähnten aktiven Störungszonen mit den aktivsten Segmenten betrachten wir als die Erdbeben-Herkrünfte, welche auf den tektonischen Zustand und die Relief-Veränderung en einwirken. Die Veränderungen aber geschehen nicht nur mit den Bewegungen wegen der Erdbeben (seismische Bewegungen), sondern auch als Folge von ständigen gleitenden Bewegungen (creeping) an den aktiven Störungen (aseismische Bewegungen). 244 Uroš Premru Abb. 2. Bedeutendere aktive Störungszonen im Krško-Einbruchstal mit den seismisch aktivsten Segmenten 1- aktive Störungszone mit seismischer Wirkungsfähigkeit M <5,0; 2- Sebent mit seismischer Wirkungsfähigkeit 5,0