Biostratigraphy of the Middle Miocene sediments in boreholes from southern Banat, Serbia

Abstract

Middle Miocene sediments in the South-West Banat area were identified based on deep exploration drilling. Based on the identified macrofauna, microfauna and microflora from 15 wells of southwestern Banat, detailed biostratigraphy of the Middle Miocene sediments was made. The biostratigraphy of the studied Middle Miocene sediments of southwestern Banat is based on the standard biozones and biozonations used in several areas of Central Paratethys (Petrovic, 1970; Jiricek, 1975; Papp & Schmid, 1985; Cicha i dr., 1998; Harzhauser & Piller, 2004, Harzhauser & Piller, 2007; Hohenegger i dr., 2014). Micropaleontological studies were performed using two methods: washed residues and thin sections method. During micropaleontological studies, the semiquantitative analysis determined relative abundance of planktonic and benthic foraminifera, as well as the presence of other fossil organisms (calcareous nanoplankton, ostracodes, molluscs). On the basis of determined foraminifera associations, two biostratigraphic zones were established into the Badenian stage and two biostratigraphic zones into the Sarmatian stage. In the Badenian sediments there are associations of foraminifera that correspond to upper levels of the Lower Badenian (Globigerinoides trilobus/Orbulina suturalis zone) and upper levels of the Upper Badenian (Ammonia beccarii/ Elphidium crispum zone). In the Sarmatian sediments there are associations of foraminifera corresponding to the lower parts of the Lower Sarmatian (Elphidium reginum zone) and the higher parts of the Lower Sarmatian (Elphidium hauerinum zone). The results of biostratigraphic research show that foraminifer zones of the Middle Miocene are not developed in the area of southern Banat (Lower lagenide zone, Spiroplectinella carinata zone, Bolivina-Bulimina zone and Porosononion granosum zone). If we consider that these biostratigraphic zones are developed in depressions south from the Sava and Danube river (Drmljanska, Markovacka, Gradistanska, etc.), it can be concluded that in the research area of southern Banat, several tectonic phases during the Middle Miocene can be registered, which will be subject to further research