FORAMINIFERS AND OSTRACODES BIOSTRATIGRAPHY OF THE BADENIAN-SARMATIAN SEDIMENTS FROM THE VCR-1 CORE, THE KOLUBARA BASIN, SERBIA

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1 FORAMINIFERS AND OSTRACODES BIOSTRATIGRAPHY OF THE BADENIAN-SARMATIAN SEDIMENTS FROM THE VCR-1 CORE, THE KOLUBARA BASIN, SERBIA S. MITROVIC¹, L. RUNDIC¹, M. GLAMOCLIJA² and D. SIJAK³ ¹Faculty of Mining and Geology, Institute for Regional Geology and Paleontology, Kamenicka 6, Belgrade, SERBIA, ¹Faculty of Mining and Geology, Institute for Regional Geology and Paleontology, Kamenicka 6, Belgrade, SERBIA, ² Int'l Research School of Planetary Sciences, Universita d'annunzio, Viale Pindaro 42, Pescara, ITALY, ³Bakusina 3, Pozega, SERBIA, Abstract: According to the reach, forams and ostracodes associations from Vcr-1 core, Badenian and Sarmatian are divided into four biostratigraphic zones: Ammonia beccarii Assemblages zone, Elphidium reginum Taxon- Range zone, Elphidium hauerinum Taxon-Range zone and Porosononion granosum Abundance zone. Finding of above mentioned microfossils indicates to the succesive deposition in a shallow, sublittoral environment. Key words: foraminifers, ostracodes, biostratigraphy, Badenian, Sarmatian, Kolubara basin The paper describes the microfauna of foraminifers and ostracodes, as well as its significance for the Badenian and Sarmatian biostratigraphy in the core Vcr-1 in the Kolubara Basin (Fig. 1). This is an investigation borehole, drilled in the range of the Project Stratigraphy of the Neogene of Kolubara Basin, in order to answer the following question: what underlies the coal-bearing Miocene. Due to technical reasons, the drilling was stopped after entering the Upper Badenian sediments. Nevertheless, abundant collected material enabled biostratigraphic division and correlation with the adjacent boreholes in which the two Miocene stages had been previously found (Mitrovic & Rundic, 1993, 1996; Petrovic & Mitrovic, 1990; Spajic et al.,

2 1986; Stevanovic, 1977). A detailed analysis of foraminiferal and ostracod fauna was performed using standard biostratigraphic methods, and biozones were distinguished according to the International Stratigraphic Guide (Salvador, 1994, Murphy & Salvador, 1999). Fig. 1. Simplified physical setting of the Kolubara basin and location of investigated borehole Vcr-1/77 Badenian sediments were discovered at the depth of m (Fig. 2). The Badenian is represented by various lithological members: clays, sandstones, carbonaceous limestones and lithothamnion limestones. Abundant and various foraminifers and ostracodes were determined in almost all sediments. Frequent zone species Ammonia beccari in association with elphidiums (Elphidium crispum, El. flexosum, El. rugosum and others) confirmed Upper Badenian Ammonia beccarii Assemblages zone. Accompanying fauna is very diverse and represented by the following forms: Heterolepa dutemplei, Nonion commune, Cibicides ungerianus, Asterigerinata planorbis, Borelis melo, Quinqeloculina akneriana, Qu. triangularis, Cycloforina contorta, etc. Ostracodes are numerous as well, and they are represented by various forms: Aurila haueri, Pokornyiella deformis, Tenedocythere sulcatopunctata and others, but they are mostly treated as accompanying fauna. Sarmatian sediments were discovered at the depth of m (Fig. 2). In the lower part of the borehole, in the interval m, the Sarmatian stage begins with sandy clays, while sandy and marly limestones and carbonaceous sandstones with intercalations of sandy clays and sands can be found in the interval m. The main characteristic of the microfaunal community is a distinct uniformity, expressed through the presence of smaller number of genera with numerous populations of certain species. Among foraminifers, forms of the Elphidium and Porosononion genera are particularly frequent. These two genera are of the primary importance for biostratigraphy of the Lower Sarmatian. Very clear changes in

3 the assemblage composition are mostly reflected in the proportional presence of representatives of these two genera, which enabled separation of three biostratigraphic zones in the Lower Sarmatian: Elphidium reginum Taxon-Range zone ( m), Elphidium hauerinum Taxon-Range zone ( m) and Porosononion granosum Abundance zone ( m). Ostracodes are represented by typical brackish association: Senesia vadaszi, Heterocythereis mehesi, Cyamocytheridea leptostigma, Loxoconcha fragilis, L. hastata, Xestoleberis glaberescense and others. Fig. 2. Lithostratigraphical succession of the core Vcr-1/77 Development of above mentioned fossil forms point to a successive sedimentation in a shallow, near-shore environment - sublittoral (Mihajlovic et al., 1997; 1998). In a paleoecological sense, two basic types of environment were distinguished: 1) marine environment during the Badenian, with prevailing mostly stenohaline forms. Exceptions are assemblages from the uppermost Badenian levels, significantly poorer in varieties, which indicates the beginning of salinity decrease; 2) reduced marine environment during the Sarmatian, i.e. a brackish biotope with mesohaline living community, connected to the upper levels of the investigated borehole. References Mihajlovic Dj., Ljupko R., Mitrovc S. & Dulic I., 1998: Miocene Microfossils of NE Bosnia and Serbia: Biostratigraphical Characteristics and Palaeoenvironmental Indicators.- Proc. 16 th Congr. Carpatho-Balcan Geol. Ass. - Vienna, Abstracts: 383p. Mihajlovic Dj., Mitrovic S., Rundic Lj. & Jeremic M., 1997: Biostratigraphical and Palaeoecological characteristics of Miocene Microfossils of NE Bosnia and Serbia (Abstracts).- Proc. 1 st Inter. Sym. App. Micropaleontol. Envir. Sci. - Tel Aviv: Mitrovic S. & Rundic Lj., 1993: Biostratigraphy of the Neogene in the Central Kolubara Basin.- Ann. Geol. Penins. Balk. (Belgrade), 57/1: (in Serbian and English) Mitrovic S. & Rundic Lj., 1996: Biostratigraphic review of the Neogene of Kolubara basin, Nortwestern Serbia.- In: Pinchuk T.N. (ed.): Sym. Neogene Stratigraphy and Paleontology of Kerch and Taman Peninsulas (Moscow/Krasnodar), IGCP Projects , Abstract: 24p. Murphy M. A. & Salvador A., 1999: International Stratigraphic Guides An abridged version.- Episodes, 22/4:

4 Petrovic M. & Mitrovic S., 1990: Sarmatian Porosononion zones of Kolubara basin.- Proc. 11 th Congr. Geol. Jugosl. Ohrid, vol. 1: (in Serbian, English summary). Salvador A., 1994: International Stratigraphic Guide, A Guide to Stratigraphic Classification, Terminology, and Procedure, 2nd ed: XIX + 214; Inter. Union Geol. Sci. & Geol. Soc. Amer. Spajic O., Petrovic M., Eremija M. & Knezevic V., 1986: The Miocene in boreholes of the Kolubara basin.- Proc 11th Congr. Geol. Jugosl. - Tara, vol. 2: (in Serbian, English summary). Stevanovic P., 1977: Miocene - Pocerina, Posavo-Tamnava, Kolubara basin.- In: Petkovic K. (ed.): Geology of Serbia Stratigraphy, Cenozoic.- Inst. reg. geol. paleont., Min. - geol. facul. Univ. Belgr. (Belgrade), (in Serbian).

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