ACTA CARSOLOGICA	30/1	6	85-96	LJUBLJANA 2001
COBISS: 1.02
DEVELOPMENT OF THE SCYTHIAN SERIES IN THE ORLICA ANTICLINE AREA (SAVA FOLDS)
RAZVOJ SKITSKE SERIJE NA OBMOČJU ORLIŠKE ANTIKLINALE (POSAVSKE GUBE)
BOGOLJUB ANIČIČ1 & STEVO DOZET1 & ANTON RAMOVŠ2
1	Geološki zavod Slovenije, Dimičeva 14, Sl-1001 LJUBLJANA, SLOVENIJA
2	Katedra za geologijo in paleontologijo, Univerza v Ljubljani, Aškerčeva 2, SI-1000 LJUBLJANA, SLOVENIJA
Prejeto / received: 20. 4. 2001
Izvleček	UDK: 551.7(497.4)
Bogoljub Aničič & Stevo Dozet & Anton Ramovš: Razvoj skitske serije na območju orliške antiklinale (Posavske gube)
Članek obravnava razvoj skitske serije na območju orliške antiklinale. Skitske plasti orliške antiklinale leže diskordantno na karbonskih in permskih kamninah. Sestavljene so iz petih litostratigrafskih členov. Starejša dva člena pripadata spodnjemu skitu ali seiskim plastem, mlajši trije pa zgornjemu skitu ali campilskim plastem v širšem pomenu besede. V peščenih plasteh seiskega zaporedja se pojavljata školjki Eumorphotis venetiana in Anodontophora, v campilskih plasteh pa polža Natiria costata in Natica, školjka Myophoria costata in foraminifera Meandrospira pusilla.
Ključne besede: stratigrafija, litološka razčlenitev, okolje nastanka, skit, orliška antiklinala, vzhodne Posavske gube, Slovenija.
Abstract	UDC: 551.7(497.4)
Bogoljub Aničič & Stevo Dozet & Anton Ramovš: Development of the Scythian series in the Orlica anticline area (Sava folds)
This paper deals with the development of the Scythian series in the Orlica anticline area. The Scythian beds of the Orlica anticline area lie discordantly upon various Carboniferous and Permian rocks. They are composed of five lithostratigraphic members: The older two members belong to the Lower Scythian, Seis beds respectively, and the younger three to the Upper Scythian, Campilian beds in the wider sense respectively. In the sandy beds of the Seis succession the pelecypods Eumorphotis venetiana and Anodontophora occur. On the other hand, in the Campilian beds the gastropods Natiria costata and Natica, as well as the pelecypod Myophoria costata and the foraminifera Meandrospira pusilla occur.
Key words: stratigraphy, lithologic dismembering, environment, Scythian, Orlica anticline, eastern Sava folds, Slovenia.
INTRODUCTION
The Orlica area with wider surroundings, treated in this article, belongs to the southeastern part of the Litija anticlinorium, the eastern Sava folds respectively, passing to the south into the Dolenjsko Karst. The Alps/Dinarides border between the Sava folds and Karst Dinarides can not be defined in this part of Slovenia as a tectonic line but as a transitional belt of minor meaning (Germovšek, 1955). However, the Orlica area is strongly folded showing here and there a complicated thrust structure. The whole area treated is cut by numerous faults that caused a block structure of the area. The borehole at Veliki Kamen, where the Triassic and Cretaceous beds are overthrusted upon the Tertiary rocks, confirms this statement. Due to the complicated structure there is no everywhere the complete cross-section of the Scythian beds in the Orlica anticline area. In spite of that it is quite possible to put together the complete cross-section, which is lithologically and paleontologically very similar to the classic Werfen development. The Paleo-zoic-Mesozoic core of the Orlica anticline is enclosed by the Tertiary sediments.
The considered area was explored by many investigators. The first who explored and described the geology of the area was Lipold (1858). Zollikofer (1861-1862) elaborated the Geological map of Orlica, Bohor and Rudnica area dividing the Triassic rock succession into the Werfen and Guttenstein limestones as well as Hallstatt limestones and dolomites. The Dreger's geological map Rogatec-Kozje on the scale of 75 000 was printed in 1907. In the Orlica region among other the Werfen beds are separated as well. The explanatory text of the map was published in 1920. The Werfen beds are separated in the Vetters Geological map of the Republick Österreich S 1:500000. Grad (1967) writes about the geology of the Kozjansko area. He found out that the Scythian stratigraphic sequence in the eastern Sava folds is composed of grey and yellow stratifed dolomite, marly limestone and sandy shale. Buser (1979) separated and described among other the Scythian beds of Bohor. Recently, the Scythian beds of the considered area were worked out by Aničic and Juriša (1984, 1985), Aničic (1991) as well as Aničic and Dozet (2000).
GEOGRAPHIC SETTING
The considered area comprises Orlica Mts. with wider surroundings, which represent the eastern prolongation of the Sava folds that sink towards the east under the Tertiary beds of the Pannonian basin. The Orlica mountains extend in the northeast-southwest direction. This mountain chain has a very expressively developed relief. The high relief of the area consists of Orlica (626 m), Veliki vrh (701 m), V. Trbojnik (653 m), Velika gora (684 m), Intermedija (662 m), Denžičev breg (588 m) Rošce (619 m), V. Špiček (693 m), V. Vagla (667 m), Kunšperk (597 m) and Marjeta (507 m). The Orlica mountain chain is cut by numerous valleys in the north-east and northwest-southeast direction. The valleys are the deepest on the northern side. The hydrogaphic net is well-developed. In the northern part of the area treated there is the a small river Bistrica leading the water off from the northern part of Orlica into the river Sotla. Other water streams flow into the river Sotla or directly into the river Sava. Larger currents of the considered area are Orlica and Sušica rivulets as well as Močnik, Dramlja, Trebčica, Glog and Čehovec smaller water streams.
METHODS
The aim of this paper is to describe the Orlica sedimentary succession and to gather paleonto-logical data for detailed lithological and biostratigraphic dismembering of the Scythian stratigrap-hic sequence as well as to find out its relations with surrounded rocks and formations. Stratimetri-cally measured and sedimentologically examined in detail are sedimentary successions in the cross-sections Pe~ice-Goli vrh, Kunej-Orli{ki potok and Orli{ki potok-Podsre{ki grad. The carbonate and clastic rocks are arranged by Folk's (1959) and Pettijohn's (1975) classifications.
STRATIGRAPHY LOWER TRIASSIC-SCYTHIAN
DISTRIBUTION
Orlica anticline and its surroundings are built of the Younger Paleozoic, Scythian, Anisian, Ladinian, Norian, Rhaetian, Cretaceous as well as Oligocene, Miocene and Pliocene rocks.
In the considered area the Scythian beds are pretty wide-spread. They can be folowed in tectonically several times interrupted belt passing from the village Pe~ice, across the Pusti vrh, Javor, Tisovec and Kun{perk towards the east as far as the Sotla river. In the study area the Scythian rocks are the most extended in the Osredek region.
LITHOLOGY
In the Orlica anticline area and its surroundings the Scythian sedimentary succession is composed of siltstone, sandstone, claystone, bedded sandy dolomite, oolitic, sparitic and micritic limestone, as well as marly limestone and marl. In the upper part of the succession nodular limestone and calcareous intraformational breccia occur here and there. The above-enumerated rocks form five lithostratigraphic members lying from bottom to top as follows: the Seis beds, the oolitic calcareous sandy member with gastropods, the Campilian beds, the limestone member with Natiria costata and Meandrospira pusilla (Fig. 1), as well as the marly and nodular limestone member.
The lower and upper boundary
The erosional-tectonic conctact between the lowermost Scythian beds, we added to the Seis member, and the underlying Younger Paleozoic rocks is exposed in the core of the Orlica anticline. The topmost Scythian limestones pass normally into the dark grey dolomite, which is according to its stratigraphic position, superposition and fossil contents ranged into the Anisian stage. Namely, in the lowermost part of the dolomite succession the foraminifers Glomospirella sp. and Glomospira sp. have been found.
Fig. 1: Location sketch map of the investigated area. Sl. 1: Lega raziskanega ozemlja.
The Seis beds
The lowermost part of the Scythian sedimentary succession in the Orlica anticline area is added to the Seis beds in narrower sense of the word. It is characterized by a rather typical and variegated sedimentation.
In the Seis stratigraphic sequence a sandstone, siltstone, marl, dolomite and limestone alternate. The sandstone is thin-bedded and fine-grained. The siltstone is very fine-stratified passing
frequently into a thin-bedded, fine-grained, siltstone and marl. All three sediments contain a pretty considerable quantity of mica. The dolomite is stratified and more or less micaceous. The limestone is micritic, stratified and platy.
The colour of the described rocks is very different. In the Seis clastic rocks the blackish red (violet) colour is predominant. The dolomites are mostly yellowish grey to yelowish brown. The limestone is dark grey.
Within the greenish grey and violet sandy shale poorly preserved pelecypods belonging to the genus Anodontophora and the species Eumorphotis venetiana Hauer occur. In the shales numerous dendrites can be seen. The thickness of the Seis beds amounts to 80 metres.
Oolitic calcareous sandy development with gastropods
Over the Seis sedimentary succession lies concordantly 65 metres thick succession, where bioclastic limestone with gastropods and pelecypods, further on, micritic and oolitic limestone as well as a limestone with iron ooids and a sandstone occur. The limestones are medium and thin-bedded (15-35 cm, 10-15 cm), brownish to dark grey or even blackish grey. Marly and clayey microsparitic limestones with frequent interlayers of oolitic and bioclastic limestones with Holo-pella gracilior (Schauroth) and Natica sp., as well as rare interbeds of brownish to dark grey stratified (15-45 cm) limestone with red iron ooids are predominant. The clayey microsparitic limestone is platy and thin-bedded. The strata are 10 cm to 25 cm thick. The rock is medium to olive grey. Here and there the limestone contains burrows with a diameter ranging from 1 mm to 4 mm. The burrows are darker than the rock passing in all directions. The clayey admixture is distributed in subparallel spots. Between the spots there are microsparitic areas. Such structure is a result of bioturbation. The burrows are filled in a part with pelmicrosparite and partly with echinoderm fragments and dolomite rombhedrons.
The sandstone is fine- to medium-grained, yellow, orange yellow and rarely greenish, platy or even very fine stratified. Beside different colours this sediment is characterized by a larger or smaller contents of mica.
Campilian beds
In the whole Scythian stratigraphic succession the Campilian member is the best developed. Fine clastic sediments such as sandstone, siltstone, claystone and shale are prevalent in its composition. Within the clastic succession are dolomite as well as marly and oolitic limestone. Prevalently clastic development of the Campilian member passes occasionally laterally into a preva-
Legend: 1- massive dolomite, 2- bedded dolomite, 3- limestone, 4- nodular limestone, 5- marly limestone, 6- oolitic limestone, 7- marl, 8- sandstone, siltstone, shale, 9- fault, 10- molluscs, 11- gastropods, 12- foraminifers (on the page 91).
Legenda: 1- masivni dolomit, 2-plastnati dolomit, 3- apnenec, 4- gomoljasti apnenec, 5- lapornati apnenec, 6- oolitni apnenec, 7- lapor, 8- peščenjak, meljevec, skrilavec, 9- prelom, 10- moluski, 11-polzi, 12- foraminifere (na strani 91).
Fig.
C7 0
2: Geological column of the Scythian beds in the Orlica anticline area. • Geološki stolpec skitskih nlasti na obmnriu orliške antiklinaie.
Legend -on the page 90. Legenda -
r^^	on
Fig. 3/1: Strongly dolomitized biooosparitic limestone with numerous fragments and sections of molluscs. Orlica, Lower Scythian, (47x).
Sl. 3/1: Mocno dolomitiziran biooosparitni apnenec s številnimi odlomki in preseki moluskov. Orlica, spodnji skit, (47x).
Fig. 3/2: Clayey microsparitic limestone with burrows. A detail of a larger burrow filled with pelmicrosparitic mud. North of Pecice, Lower Scythian, (19x).
Sl. 3/2: Glinasti mikrosparitni apnenec z rovi (burrows). Detajl vecjega rova zapolnjenega s pelmikrosparitom. Severno od Pecic, spodnji skit, (19x).
Fig. 3/3: Myophoria costata Zenker in grained limestone. At the road Goli vrh-Pecice, Upper Scythian, (2x).
Sl. 3/3: Myophoria costata Zenker v zrnatem apencu. Ob cesti Goli vrh-Pecice, zgornji skit, (2x).
Fig. 3/4: Meandrospira pusilla (Ho) in a strongly recrystallized limestone. Orlica, (250x). Sl. 3/4: Meandrospira pusilla (Ho) v mocno rekristaliziranem apnencu. Orlica, (250x).
lently dolomitic development with intercalations of clastic sediments. In the study area the Cam-pilian member is characterized beside the variegated lithological composition also by variety of colours and large contents of mica. The most colourful are clastic sediments appearing in various shades of red colour and sometimes in bluish, yellowish and greenish grey colour. The dolomite is yellowish grey to orange yellow and in spots pinky.
The limestone is moderate dark grey and brownish yellow (if it is weathered). The dolomite is stratified (15-35 cm). Within the dolomite beds accumulations of mica can be observed. The mica is recognizable still with the naked eye in the dolomite as well. In spots the dolomite shows an oolitic structure, but it mostly occurs in the form of dolomicrite or dolosparite. The limestone is micritic or fine-oolitic. Sometimes it can be bioclastic containing numerous mollusc fragments.
The limestones with pelecypods, gastropods and foraminifers
Concordantly and without interruption over the Campilian member lies dark grey, greyish black and black, platy and stratified (10-60 cm) micritic and grained limestone containing frequently white calcite veinlets. In the basal bed of that interval of the Scythian lithological column occur very well-shaped gastropods of the species Natiria costata (Münster). In the stack of micri-tic limestone rare interbeds of oolitic limestone as well as rare beds of bioclastic-limestone with rare pelecypods and gastropods of the genus Natica can be observed. In the fossil material the pelecypod Myophoria costata Zenker (Fig. 3/3) is found out. In the thin-sections of the sparitic limestone the foraminifer Mandrospira pusilla (Ho) is determined (Fig. 3/4).
The thickness of the described sedimentary succession ammounts to 30 metres.
Marly and nodular limestone
In the topmost part of the Scythian lithological column there is about 8 to 10 metres thick stack of platy and thin-bedded (1-15 cm) dark grey marly limestone with schistose structure and yellowish to orange oxide cover containing rare thin interlayers of oolitic limestone. In the finegrained limestone the foraminifer Meandrospira pusilla (Ho) has been found. On the other hand, in the bioclastic limestone at the top of the Scythian sedimentary stack, the gastropod Natiria costata (Münster) and the pelecypod Myophoria costata (Zenker) have been found.
The considered lithologic member is terminated by a 60 centimetre thick bed of greyish red oolitic limestone with the gastropod Holopella gracilior (Schauroth).
SEDIMENTARY ENVIRONMENT
In the Orlica anticline area and its surroundings a shallow restricted sea predominates in the Scythian period, where sand and ooids have been episodically and periodically brought by currents and waves. The groundmass between ooids was formerly micritic and later recrystallized into a microsparite and very fine-grained sparite. The micritic groundmass indicates a calm water. Microsparitic clayey limestone proves a calm sedimentary environment as well. Partly early dia-genetic dolomitization of limestone and an occurrence of fine-grained sparitic dolomite speaks for a shallow water and episodical desiccation in the supralittoral belt.
CONCLUSIONS
The variegated sedimentary succession in the Orlica anticline area, which is ranged into the Scythian series, lies discordantly upon the Permo-Carboniferous dark grey to black shales, quartz sandstones and conglomerates passing upwards normally on to the concordantly overlying moderate grey stratified Anisian dolomite with foraminifers Glomospira sp. and Glomospirella sp.
In the considered area the Scythian series is subdivided into 5 lithostratigraphic members; namely: 1) - Seis beds, 2) - oolitic limestone-sand member with gastropods, 3) - Campilian beds, 4) - limestone member with Natiria costata and Meandrospira pusilla and 5) - marly and nodular limestone. In the lithologic composition of the Seis beds stratified and massive, red and violet red, rarely greenish grey quartz sandstones with interbeds of claystones as well as clayey shales, dolomites and limestones occur. In the sandy shales the pelecypods Anodontophora sp. and Eu-morphotis venetiana have been found.
In the oolitic limestone-sand member bioclastic limestones with Holopella gracilior, micritic and oolitic limestone, limestone with iron ooids and quartz sandstone alternate. In the southern Sava folds in the Orlica anticline area the Campilian beds are most colourfully developed. In its composition fine-grained sediments such as sandstones, siltstones, claystones and clayey shales prevail. Within the described succession interbeds of dolomite as well as marly and oolitic limestones occur. In the Campilian member no fossils have been found yet.
Concordantly upon the Campilian sediments lies the succession of the dark grey to black, prevalently bedded micritic and grained limestone with white calcite veinlets, well-preserved
gastropod Natiria costata shells and Natica, as well as the pelecypod Myophoria costata and foraminifer Meandrospira pusilla. The Scythian series is terminated by a 60 cm thick bed of greyish red oolitic limestone with the gastropod Holopella gracilor.
ACKNOWLEDGEMENTS
The authors are much obliged to the Ministry of Science and Technology as well as to the Geological survery of Slovenia for financial support, which enabled the investigations in the field.
REFERENCES
ANIČIČ. B., 1991: Geološke razmere na Orlici. Geologija; 33: 233-287, Ljubljana. ANIČIČ, B. & JURIŠA, M., 1984: Osnovna geološka karta SFRJ, list Rogatec M 1:100 000.
Zvezni geološki zavod, Beograd. ANIČIČ, B. & JURIŠA, M., 1985: Tolmač za list Rogatec. Osnovna geološka karta SFRJ
M 1:100 000. Zvezni geološki zavod, 76 str., Beograd. ANIČIČ , B. & DOZET, S., 2000: Mlajšepaleozojske in mezozojske kamenine na severnem obrobju
Krške kotline. Geologija; 43/1: 13-35, Ljubljana. BUSER, S., 1979: Tolmač lista Celje. Osnovna geološka karta SFRJ M 1:100 000. Zvezni geološki zavod, 72 str., Beograd. DREGER, J., 1907: Geologische Karte Robitsch-Drachenburg, Wien.
DREGER, J., 1920: Erläuterung zur Geologischen Karte Robitsch und Drachenburg. Geol.S.A., 42 str., Wien.
FOLK, R. L., 1959: Practical petrographic classification of limestones. Amer. Ass. Petrol. Geol. Bull.; 43/1:1-38, Tulsa.
GERMOVŠEK, C., 1955: O geoloških razmerah na prehodu Posavskih gub v Dolenjski kras med
Stično in Šentrupertom. Geologija; 3: 235-239, Ljubljana. GRAD, K., 1967: Geologija Kozjanskega. Geogr. zbornik; 4. razr. SAZU, 10: 7-16, Ljubljana. LIPOLD, M. V., 1858: Bericht über die geologische Aufnahme in Unterkrain im Jahr. 1857. Jb.
Geol. R.-A., Bd 9: Wien. PETTIJOHN, F. J., 1975: Sedimentary rocks. Harper & Row, Publishers, 628 str., New York. VETTERS, H., 1933: Geologische Karte der Republik Österreich und der Nahbargebiete 1:750 000.
Geol. Bundesanstalt; Wien. VETTERS, H., 1937: Erläuterungen zur Geologischen Karte der Republik Österreich und seinen
Nachbargebieten. Geol. Bundesanstalt; 343 str., Wien. ZOLLIKOFER, Th. 1861-1862: Über die geologischen Verhältnisse der südöstlichen Theiles von Untersteiermark. Jahrb. Geol. R.-A; 12: 311-366, Wien.
RAZVOJ SKITSKE SERIJE NA OBMOČJU ORLISKE ANTIKLINALE
(POSAVSKE GUBE)
Povzetek
Pestro zaporedje sedimentov na obmo~ju orli{ke antiklinale, ki smo ga uvrstili v skitsko serijo, leži diskordantno na karbonskih in permskih temno sivih do ~rnih glinenih skrilavcih, kreme-novih pe{~enjakih in konglomeratih, navzgor pa prehajajo brez prekinitve v konkordantno leže~i srednje sivi, plastnati anizijski dolomit s foraminiferama Glomospira sp. in Glomospirella sp.
Skitska serija je na obravnavanem ozemlju raz~lenjena na 5 litostratigrafskih ~lenov (od spodaj navzgor): 1) - seiske plasti, 2) - oolitni apnen~evo pe{~eni ~len s polži, 3) - campilske plasti, 4) - apnen~ev ~len s {koljkami, polži in foraminiferami in 5) - lapornati in gomoljasti apnenec.
V	sestavi seiskih plasti prevladuje plastnati in masivni, rde~i in vijoli~asto rde~i, redkeje zelenkasto sivi kremenov pe{~enjak z vložki glinovca, glinenega skrilavca, dolomita in apnenca.
V	pe{~enem skrilavcu se pojavljajo {koljke Anodontophora sp. in Eumorphotis venetiana.
V	oolitnem apnen~evo pe{~enem ~lenu se menjavajo bioklasti~ni apnenec s polži Holopella gracilior, mikritni in oolitni apnenec, apnenec z železovimi ooidi ter kremenov pe{~enjak.
V	južnih Posavskih gubah je na obmo~ju orli{ke antiklinale najbolj pestro razvit campilski ~len. V njegovi sestavi prevladujejo drobnoklasti~ni sedimenti pe{~enjak, meljevec, glinovec in glineni skrilavec. Vmes se pojavljajo vložki laporja, dolomita ter lapornega ali oolitnega apnenca.
V	campilskem ~lenu niso najdeni fosili. Konkordantno na campilskih sedimentih leži skladovnica temno sivega do ~rnega pretežno plastnatega mikritnega in zrnatega apnenca z belimi kalcitnimi žilicami in lepo ohranjenimi hi{icami polžev Natiria costata in Natica sp. ter s {koljko Myopho-ria costata in foraminifero Meandrospira pusilla.
Skitsko serijo zaklju~uje skladovnica temno sivega tankoplastnatega, plo{~astega in skrilave-ga lapornega apnenca, ki navzgor prehaja v drobnogomoljasti apnenec s foraminifero Meandros-pira pusilla in polžema Natiria costata in Natica sp. Skitsko serijo zaklju~uje 60 cm debela plast sivkasto rde~ega oolitnega apnenca s polžem Holopella gracilior.
ZAHVALA
Ministrstvu za znanost in tehnologijo in Geološkem zavodu Slovenije se avtorji tega ~lanka zahvaljujemo za financiranje, ki nam je omogočilo izvajanje kompleksnih geoloških raziskav.