REGIONALNI OBSEG LIBURNIJSKIH PLASTI
Rajko Pavlovec
Plasti med zgornjo kredo in eocenom v jugozahodni Sloveniji ter
Istri je Stäche imenoval liburnijsko stopnjo. Objavil je vrsto opazo-
vanj, katerih rezultate je združil v obsežno monografijo (Stäche, 1889).
V zadnjem času je bilo poudarjeno, da liburnijska stopnja ni pravilno ime,
ker te plasti obsegajo več stopenj: spodnji, srednji in zgornji paleocen
(Pavlovec, 1963).
Klasična nahajališča liburnijskih plasti so v raznih delih jugozahodne
Slovenije, lepe profile z nekoliko specifičnim razvojem pa dobimo tudi
južneje v Istri (Pazin, Labin, Raša). Del liburnijskih plasti je sicer lahko
sladkovodnega nastanka, vendar je več brakičnih ali morskih plasti, kot
so mislili doslej (Pavlovec, 1963). Poudariti je treba še to, da so bile
najdene pogostne foraminifere tudi v plasteh s številnimi oogoniji haracej.
Vendar morje ni moglo biti odprto ali globoko. Poleg favne kaže na to
hitro horizontalno in vertikalno spreminjanje sedimentov.
Liburnijske plasti moramo torej definirati stratigrafsko (spodnji in
srednji paleocen ter spodnji del zgornjega paleocena), paleontološko
{Cosinia, Stomatopsis, Orhitolites, Coscinolina, Operculina, Rhipidionina,
Rhapydionina, miliolide, Chara itd.) in petrografsko (horizontalno in ver-
tikalno hitro se menjavajoči navadno precej bituminozni apnenci in la-
porji, ponekod vložki premoga). Po takšni definiciji lahko istrske terciarne
sedimente pri Labinu in Pazinu imenujemo liburnijske plasti, čeprav
vključujejo že facialne različke (npr. plasti s Perna sp., debeli vložki
premoga itd.).
Cim dlje gremo od klasičnega ozemlja liburnijskih plasti, tem teže
pričakujemo takšne sedimente. V Dalmaciji, Bosni in Hercegovini jih sicer
ugotavljajo, vendar doslej ni nikjer znanih dobrih profilov. To ime so
dobili zaradi stratigrafske lege (ki pa še ni povsem jasna) in fosilov
(miliolide, haracej e in drugo).
Normalno nadaljevanje liburnijskih plasti sledimo v Furlaniji, kjer
pa so zelo redko razkrite. Najzahodnejše najdišče je Monte di Medea
kake 4 km jugozahodno od Krmina (Desio in Martinis, 1950;
Martinis, 1962).
Bonni in Vanos si (1960, 45) omenjata, da spominjajo nekatere
plasti in favna v zahodni Liguriji na brakični paleocenski razvoj (»Li-
burnico«). Richter (1961, 117) gre še dalje in te plasti označuje kot
»liburnijska stopnja«. Pravi, da petrografsko in favnistično zelo spo-
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minjajo na Stachejeve moncijske kozinske apnence. V njih je našel
ostreje, Cirene, ceritije in haraceje.
Za zahodno Liguri j o velja toliko bolj pripomba, ki smo jo podali
za Dalmacijo, Bosno in Hercegovino. Razdalja je prevelika, da bi tam
mogli iskati podaljšek plasti, ki so nastale v bazenu z dokaj specifičnimi
sedimentacijskimi in najbrž tudi tektonskimi procesi.
Zanimivo je nadalje še to, da se liburnijske plasti pojavljajo v ba-
zenu, ki ga na severu obdajajo Alpe, na jugu pa nenaguban plato
(cf. Richter, 1962, 469 in 472). Ne da bi se podrobno spuščali v problem
tega platoja, moramo ugotoviti, da na njem kakor tudi v Alpah ni libur-
nijskih sedimentov. Ce je bil plato v paleocenu res nekaka stabilna masa,
so torej nastale liburnijske kamenine v manjšem bazenu. Čeprav bi imel
ta zvezo s kakim drugim bazenom zahodno od platoja, sedimentaci j ski
pogoji ne bi mogli biti enotni v obeh kadunjah. Tudi to govori proti
liburnijskim plastem v zahodni Liguriji.
Richter (1962, 475) podaja nadalje pripombe h Kossmatu
(1913) oziroma Winklerju (1924). Prvi je prišteval Trnovski gozd in
Hrušico Dinaridom, drugi Alpam. Richter poudarja, da so triadne in
jurske plasti enako razvite od Velebita preko Snežnika do Hrušice in
Trnovskega gozda. Podobno je tudi s kraško kredo. Temu moramo dodati
dejstvo, da se pojavljajo rdeči laporji in skrilavci (»scaglia«) tudi na južni
strani Trnovskega gozda in Hrušice. Te plasti pa so značilne za Alpe.
Meja med obema gorstvoma je torej še vedno nerešeno vprašanje. Sedi-
mentaci j ski bazen v najstarejšem terciar j u je imel brez dvoma tesno
povezavo z dogajanji na alpskem in dinarskem delu, zakaj nastal je prav
tam, kjer so bile stične točke med obema gorstvoma najtesnejše.
REGIONAL EXTENT OF THE LIBURNIAN STRATA
The strata between the Upper Cretaceous and Eocene in south western
Slovenia and Istria have been termed Liburnian by Stäche; he had
published a great many observations the results of which were united
in his extensive monography (Stäche, 1889). It has been recently
pointed out that the Libumian sediments include several stages Lower,
Middle and Upper Paleocene (Pavlovec, 1963). The classic finding
places of the Liburnian strata are in various parts of south western Slo-
venia and fine sections with a rather specific development can be also
found in the southern Istria (Pazin, Labin, Raša). A part of the Liburnian
strata might be of fresh-water origin, but there are more brackish-water
or marine sediments as it has hitherto been assumed (cf. Pavlovec,
1963). It is necessary to emphasise here that a lot of foraminifers have
been found in the strata with numerous oogonia of Characeae. But the
sea could have been neither open nor deep; besides fauna as well the
fast changing of sediments in both the horizontal and the vertical
direction are pointing to it.
The Liburnian strata have to be defined: 1. stratigraphically (the
Lower Paleocene, the Middle Paleocene, and lower part of the Upper
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Paleocene); 2. paleontologically {Cosinia, Stomatopsis, Orhitolites, Coscino-
lina, Operculina, Rhipidionina, Rhapydionina, Miliolidae, Chara etc.);
3. sedimentologically (various, horizontally and vertically fast alternating,
usually rather bituminous limestone and marl, in some place coal inter-
calations). According to such a definition we may the Istrian Tertiary
sediments at Labin and Pazin call Liburnian strata, though they include
facial varieties already (e. g. strata with Perna, thick coal intercala-
tions etc.).
The further we go away from this classical region of the Liburnian
strata the harder we expect to get such sediments. In Dalmatia, Bosnia
and Herzegovina investigators are identifying them, but until now no
good sections have been known there. The strata have been named as
Liburnian according to their stratigraphie position (which has not been
cleared yet entirely) and because of the fossils (Miliolidae, Chara-
ceae etc.).
A normal continuation of the Liburnian strata we trace in Furlania,
where they are very rarely revealed. The westernmost finding place is
Monte di Medea about 4 km. SW of Cormons (Desio and Martinis,
1950; Martinis, 1962).
Bonni and V a n o s s i (1960, 45) mentioned that some strata and
the fauna in western Liguria remind of the brackish-water Paleocene
sediments ("Liburnico"). Richter (1961, 117) even defined these strata
as "Liburnian series"; he stated that they were very much alike the
S t a c h e' s Montian Kozina limestones, petrographically and faunistically.
He had found Ostrea sp., drena sp., Cerithium sp. and Characeae in them.
What has been said for Dalmatia, Bosnia and Herzegovina is even
more suitable for western Liguria. It is too great distance that we could
search there for the extension of strata which have originated in a basin
with rather specific sedimetary processes, and probably tectonic ones too.
Of the further interest is the fact that the Liburnian strata occur
in a basin surrounded in the north by the Alps and in the south by a not
folded plateau (cf. Richter, 1962, 469 and 472). Without enter into
details of the problem of this plateau we have to state here that on it as
well as in the Alps there are no developed Liburnian sediments. If the
plateau really acted as a stable mass in the Paleocene then the Liburnian
rocks originated in a smaller basin, even if the latter had had the con-
nections with any other basin westward of the plateau, the conditions
of sedimentation could not have been uniform in both basins. And this,
too, denies the existence of Liburnian strata in western Liguria.
Then Richter (1962, 475) gave some observations on K o s s m a t
(1913) and Winkler (1924) respectively. The former regarded Trnovski
gozd and Hrušica as parts of the Dinaric Alps, the latter assigned them
to the Alps. Richter is pointing out that the Triassic and Jurassic
strata are equally developed from Velebit over Snežnik to Hrušica and
Trnovski gozd and so is with the Dinaric Cretaceous. Here the fact to be
added that the red marls and shales ("scaglia") also occur on the southern
side of Trnovski gozd and Hrušica. These strata, however, are a
characteristic of the Alps. The border between the two mountain systems
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is still an unsolved problem. In the oldest Tertiary the sedimentation
basin was without doubt closely connected with the occurrences in the
Alpine and Binarie part; it originated just there where the convergent
points between the two mountain systems were the firmest.
LITERATURA
Bonni, A., in Vanossi, M., 1960, Ricerche e considerazioni sul
Flysch della I.iguria occidentale. — Atti 1st. geol. Univ., 11, 31—178, tab. 3.
Pavia.
Desio A. in Martinis, B., 1950. Notizie sulla costituzione geologica
del Monte di Medea nel Friuli. — Boll. Soc. geol. ital., 69, 50—59. Roma.
K o s s m a t, F., 1913. Die adriatische Umrandung in der alpinen Falten-
region. — Mitt. Geol. Ges., 6, 61—165, 1 tabela. Wien.
Martinis, B., 1962, Ricerche geologiche e paleontologiche sulla regione
compressa tra il T. ludrio ed il F. Timavo (Friuli orientale). — Riv. ital.
paleont. strat., Mem. 8, 1—245 (tab. 1—22), 9 prilog, 1 geol. karta. Milano.
Pavlovec, R., 1963, Stratigraski razvoj starejšega paleogena v južno-
zahodni Sloveniji (Die stratigraphische Entwicklung des älteren Palaeogens im
südwestlichen Teil Sloweniens). — Razprave Slov. akad. znan. umet., Cl. IV, 7,
419—556, 1 tabela. Ljubljana.
Richter, M., 1961, Über den Bau der Ligurischen Alpen. 3. Tektonik
und Stellung der Flyschzone. — Z. Deutsch, geol. Ges. —113, 116—149. Hannover.
Richter, M., 1962, Alpen, Apennin und Dinariden. — N. Jb., Monatsch,
466-480. Stuttgart.
Stäche, G., Die Liburnische Stufe und deren Grenz-Horizonte. — Abh.
Geol. R. A., 13, 1—170, tab. 1—8, geol. karta. Wien.
W i n k 1 e r , A., 1924, Ueber den Bau der östlichen Südalpen. — Mitt. Geol.
Ges., 16, 1—272, tab. 1—4. Wien.
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