GEOLOGICA BALCANICA. 26. 2, Sofia, Jun. 1996, p. 45-50

Mesozoic sections of biostratigraphic and palaeontological importance in the Stara Planina Mountains

J ovanka M itrovic-Petrovic, Vladan Radulovic

butitute of Regional Geology and Palaeontology, Faculty of Mining and Geology, Uni'versity of Belgrade, KmneniCka Str. 6, P.O.Box 227. 11001 Belgrade

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Abstract. The Stara Planina Mountains includes sedimentary rocks of different ages, beginning with the Proterozoic and ending with the Plio-Quaternary. Most widespread are Mesozoic rocks which are highly fossiliferous. The abundant fossil fauna was used in identifying the presence of all Triassic, Jurassic and Cretaceous stages. Most instructive sections within the three sistems are presented, which in our opinion should be protected. Noteworthy is the traceable continuous transition from one stage to another within a relatively small area.

Mitrovic-Petrovic, J., Radulovic, V. 1996. Mesozoic sections ofbiostratigraphic and palaeontological - portance in the Stara Planina Mountains.- Geologica Bale., 26, 2; 45-50.

Key words: Stara-Planina Mountains; Mesozoic; Instructive sections; Fossil fauna; Biostratigraphy; Paleontology

Introduction

Sedimentary rocks of different geologic age m the Proterozoic to the Plio-Quaternary, ven with fossil fauna and flora) crop out in

e Stara Planina Mountains. Most widespread the Mesozoic sediments, which are also most

,..ossiliferous. The fossils found include almost groups of Mesozoic invertebrates: Forami-

. era, Infusoria, Radiolaria, Spongia, Anthozoa, Gastropoda, Bivalvia, Nautiloidea, Ammono-- ea, Belemnoidea, Bryozoa, Brachiopoda, Crinoidea, and Echinoidea. The abundance of ossil fauna enabled a precise breakdown of

tigraphy. All stages of the Triassic, Jurassic d Cretaceous have been identified. The stratigraphy and paleontology of the

region have been studied by many geologists, to ention only some of them: Protic (1934),

Andelkovic (1958, 1962, 1964, 1966), Andelkovic and Javidpour (1966), SuCic-Protic (1969, 1971, 1985), Urosevic (1971), Mitrovic-Petrovic, (1974), Jankisevic (1978, 1982), Mitrovic-Petrovic, Radulovic (1994), Radulovic (1982), Urosevic et al. (1992), etc.

1. Jelovica-Rsovci stretch

The entire stretch of about 8 km from Jelovica village to Rsovci village (Fig. 1 ), that is all sections at the Jelovica-Rsovci road, should be protected, because they expose the stratigraphic succession of all Triassic (Pl. 1, figs 1-4), Jurassic (Pl. 1, figs 5, 6; Pl. 2, figs 1-3) and Lower Cretaceous (Pl. 2, figs 4-7) stages. If the preservation is not possible, we recommend preservation of the extremely fossiliferous:

a. Middle Triassic section at Vrelo, and

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Fig. I. Map of Stara Planina Mountains showing the geological sites described: 1. Jelovica village, 2. Vrelo, 3. Monastery of St. Bogorodica, 4. Visock:a Riana village, 5. Rsovci village, 6. Sk:uvija, 7. Grlja, 8. Mountain house

b. Liassic section at the Monastery of St. Bogorodica.

a. Section of Middle Triassic limestones at Vrelo (Fig. 1)

Lower levels of the limestones contain a rich dominan~ly bivalvian fauna: Plagiostoma striatum (Schlotheim), Velopecten albeni (Gold.), etc. (Pl. I, fig. 3). From Vrelo toward Visocka Rzana, these limestones are succeeded by dolomitic limestones with numerous brachio-pods: Decurtella decunata (Gir.), Punctospirella fragilis (Schlotheim.), Mentzelia mentzeli (Dunk.), Tetractinella trigonella (Schloth .. ), Coenothyris vulgaris (Schloth.), Silesithyris angusta (Schloth.) (Urosevic et al., 1992). The above-lying limestones with crinoids and diploporids are the uppermost Anisian formation (Pl. I, fig. 4). Upward follow massive, slightly dolomitic limestones of Ladinian age at the end of Triassic development in the region. Upper Triassic formations are lacking.

b. Section of Liassic sediments at Monastery St. Bogorodica

Triassic limestones are succeeded by quartz sandstones of the Lower Jurassic over a small area. On the left side of the Jelovicka River, facing the Monastery, exposed are Middle Liassic (Lower Pliensbachian) sediments in terrigenous-carbonate development with sandy limestones, marlstones, shales, and siltstones abounding in brahiopods (Sucic-Protic, 1969, 1971, 1985), bivalves (Radulovic, 1982), and belemnites. The commonest brachiopods are: Tetrarhynchia argotinensis (Rad.), Lobothyris punctata (J. Sow.), Zeilleria (C. ) numismalis (Lam.), Liospiriferina rostrata (Schloth.). Most

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frequent among belemnites are the species: Belemnites elongatus Mill., B. paxilosus Schloth. A frequent bivalvian genus is Gryphaea and its species: G. arcuata (Lam.), G. cymbium (Lam.); followed by Pholadomya species: Ph. idea Ag., Ph. decorata Ziet., Ph. glabra Ag. etc., after followPseudopecten (Ps.) equvalvis (J. Sow.); and representatives of other genera and species. Liassic sediment can be traced over a length of about 200 metres, to Dogger sediments, the next in the succession (Pl. I, fig. 5, 6).

2. Section of Upper Cretaceous sediments of Grlja

The Grlja valley is situated near the mountain house (Carev KJadenac spring) below the 12-km milestone of the Pirot-Visocka Riana road. The valley lies between mountains peaks of Crni Vrh (1151 m) in the west, Basarski Kamen (1371 m) in the south, Skuvija (I 089 m) in the east, and Grlja and Tepavac slopes in the north (Fig. 1).

The best studied section runs from Grlja slope to the Grlja brook to the new Pirot-Visocka Riana road. Descending from the mountain house to the Grlja valley, one can observe sandstones, tuffites and tuffaceous calcarenites with faunal fossils. These deposits generally extend west-east, traceable over some six kilometres. The rocks vary in composition, known as the Grlja Series, and contain small Bryozoa (genus Onychochella), Brachiopoda (Orbyrhynchia mantelliana (J. de C. Sow.), Terebratulina protostriatula Owen, Cyclothyris sp.), a few representatives of Inoceramus, and Crinoidea (Pentacrinus nodulosus Roem., P. carinatus Roem. (Mitrovic-Petrovic & Radulovic, 1994).

Conformable over tuffite beds lie marlstones, sandy marlstones and thin -platy sandstones. Identified foraminifers, from samples gathered from bed to bed beginning from the contact wih tuffite, were used by Andelkovic (1964) in separating nine foraminiferal levels: three corresponding to the Turonian and six to the Senonian formations. Apart from foraminifers, marlstones contain many inocerams, and are separated as inoceramus-foraminiferal marlsto-nes. Faunal assemblages also include few ammonitic remains and echinoids. The commonest inoceram species are: Inoceramus diformis Meek, I. lamarcki Park., I. cordiformis Sow., etc. The identified echinoids are:Discoidea minima Ag.,Hemiaster sannio Lamb., H. cristatus Stol., Guettaria angladoi Gauth. (Mitrovic-Petrovic, 1974). Megafauna was collected in a broad belt from down the southern Grlja slope to the Grlja brook. The gathered specimens were

mostly washed out, found at the surface of much weathered marlstones, that could not be used in placing the boundary between Turonian and Senonian deposits. The transition from the Turonian into the Senonian is not noticeable in the uniform lithology.

3. Section of Barremian-Aptian (Urgonian) sediments in the Skuvija area

Skuvija Hill (1 089 m above sea level) rises at the road between Carev Kladenac mountain house and Rsovci. In its southern slopes and in road cuttings between 15 km and 16.5 km of road length, Barremian-Aptian sediments in Urgonian development are exposed (Fig. I). These rocks are characterized by facial diversity:

-Facies of limestones with rudists (Toucasia carinata Math., Requienia ammonia (Goldf.), Monop/eura coquandi Math., etc.);

- Facies of limestones with corals (Hyd-nophora picteti Koby, Eugyra digitata Koby, Thecosmi/ia tob/eri Koby, etc.);

- Facies of bioclastic limestones with terrigenous admixtures and bivalves (Ostrea), gastropods (Nerinea), and echinoids (numerous spines of "Cidaris", Pygaster truncatus Ag., Pyrina cy/indrica Gras., etc.);

- Facies of orbitolinid sandstones; - Facies of medium- and coarse-grained

sandstones with ostrean shell detritus and coalified plant detritus;

- Facies of sandy marlstone with Bedoulian ammonites.

Conclusion

I. Stara Planina Mountains offer excellent opportunities for any geological investigation, but our presentations are limited to biostra-tigraphy and paleontology.

2. Particularly significant are Mesozoic deposits, which have greatest distribution and are most fossiliferous.

3. Apart from the few selected and presented sections, there are many others which are not mentioned here but ought to be protected. These are primarily:

a. Section of Triassic limestones in Gostucka Reka (Lukanja village),

b. Section of Jurassic sediments at Rosomac village, .

c. Section of Upper Jurassic sediments in Senokos-Kamenica stretch.

References

Andellcovi~. M. 1958. Geolo!lci sastav i tektonika Stare planine. - Srp. Akad. nauka, Pose b. izd. J 17, Odelj. prir. maL nauka, 24; 1-48.

Andellcovi~. M. 1962. Biostratigrafija donje jure Stare pia nine na osnovu amonita. - Geol. anali Balk. poluost, 29; 1-11'

Andellcovi~. M. 1964. Turonslci kat na Staroj planini i mogu~nost njegovog izdvajanja u drugim oblastima Jstotne Srbije. - Geol. anali Balk. poluost., 31; 1-8.

Andellcovi~. M. 1966. Amoniti iz slojeva sa Aspidoceras acanthicum Stare planine (isto~na Srbija). - Paleont. JugosL, 32; 1-7, Zagreb.

Andellcovi~. M., Javidpour, M. 1966. Biostratigrafija batslcog kata izmedu sela Senolcos i Kamenica (Stara planina). - GeoL anali Balk. poluost., 32; 1-7.

Janlci§evic, J. 1978. Baremslci i aptslci kat u srednjim delovima Karpato-ballcanida isto~e Srbije sa posebnim osvrtom na urgonslco razvi~e. - Geol. anali Balk. poluost., 42; I 03-190.

Janlci§evic, J. 1982. Nalazalc cefalopoda u aptslcim sedimentima Slcuvije (Stara plan ina). - Geol. anali Balle. poluost., 46; 259-261.

Mitrovic-Petrovic, J. 1974. Kredni ehinidi Stare planine. - Geol. an ali Balk. poluost.. 41; 181-202.

Mitrovic-Petrovic, J ., Radulovic, V. 1994. Fosilna fauna iz cenomanslcih tufitskih slojeva Grlje (Stara planina, isto~na Srbija). - Geol. anali Balk. poluost., 58 (1); 119-138.

Protic, M. 1934. Geolo§lci sastav i tektonika Stare planine. -Rasp. geol. inst. Kralj. JugosL, 4; 1-139, Beograd.

Radulovic V. 1982. Lijaslca lamelibranhijatska fauna JZ pad ina Stare planine (istoena Srbija).-GeoL anali Balk. poluosL, 41; 293-324, Beograd.

Su~ic-Protic, Z. 1969, 1971, 1985. Mesozoic Brachiopodtl of Yugoslavia. Middle Liassic Brachiopoda of the Yugoslav Carpatho-Balkanids. I: 1-93, Univ. Belgrade Monogr. (1969); 2: 1-63, Univ. Belgrade Monogr. (1971); 3: 1-60, Paleont. Jugosl., 32, Zagreb (1985).

Uro!evic, D. 1971. Pregled trijaslce faune i flore Stare planine (Karpato-ballcanslci pojas). - GeoL anali Balle. poL, 36; 95-103.

Uro§evic, D., Radulovic, V., Pe§ic, L. 1992. Middle Jurassic (Anisian) brachiopods from the Yugoslavian Carpatho-Balkanides. -Rev. Paleobiol .• 11 (2); 469-481, Geneve.

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PLATE 1

F~g. 1 Lower Triassic (Seisian beds) variegated sandstones. Jelovica Fig. 2 Lower Triassic (Campilian beds) limestones with fauna. Jelovica Fig. 3 Middle Triassic (Anisian) nodular limestones. Vrelo Fig. 4 Middle Triassic (Ladinian) dolomitic limestones with crinoids. Vrelo Fig. 5 Middle Liassic (Lower Pliensbachian) sediments. Monastery SL Bogorodica Fig. 6 Middle Liassic (Lower Pliensbachian) sediments - detail with fosails. Monastery SL Bogorodica

PLATE2

Fig. 1 Dogger sandstones. Jelovica River Fig. 2 Kimeridsian limestones (Acanthicw beds). Jelovica River rJg. 3 Boundary between Dogger sandstones (a) and Oxfordian limestones (b). Jelovica River Fig. 4 Lower Creta.ceous (Berriasian-Valanginian) marly limestones with cherts. Above Visot\ka lUana villag Fig. 5 Lower Ceretaceous (Berriasian-Valanginian) marly limestones and marls. Above Visot\ka lUana villqe Fig. 6 Lower Cretaceous (Berriasian-Valanginian) limestones and marls. Above Visot\ka R.Zana village Fig. 7 Lower Cretaceous (Valanginian) limestones and marls. Above Visot\ka lUana village

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PLATE I

49

PlATE II

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