AN UPDATE ON THE STRATIGRAPHIC LIMITS OF UPPER CRETACEOUS FROM LEBADA EAST STRUCTURE, ISTRIA BASIN, WESTERN BLACK SEA.

The main purpose of this paper is to provide new geological information and interpretation of the well data from the Istria Basin, Western Black Sea. Therefore, we present a reconsideration of the microfaunas (mainly foraminifers) and calcareous nannofossils described from several wells drilled on the Lebada East structure belonging to the Istria Basin, by using core reports. Thus, we have been able to compile integrated information regarding the lithology and biostratigraphy of the wells. We have focused on the stratigraphy of the Upper Cretaceous deposits, placed in between the uppermost Lower Cretaceous (i.e., the Albian) sediments and the Eocene ones. Among the investigated wells, we present in this paper one well situated in the Lebada East structure. The drilled sediments are argillaceous sandstones and sandy-argillaceous limestones Cenomanian, followed by Santonian deposits, showing a similar lithology as above-described. Fossiliferous calcareous sandstones were deposited in the Campanian-lower Maastrichtian. The uppermost Cretaceous, i.e., the upper part of the Maastrichtian is composed of micritic limestones. The Upper Cretaceous stages have been distinguished by using planktonic foraminiferal biozonation. Hence, the Cenomanian was pointed out based on the presence of an assemblage with Thalmanninella appenninica, T. brotzeni and Rotalipora cushmani, while the upper Santonian depositional interval contain the planktonic foraminifers Dicarinella concavata and Globotruncana mariei, as significant biostratigraphic species. The Campanian-lower Maastrichtian depositional interval was pointed out by the presence in the calcareous nannofossil assemblage of the taxa Uniplanarius trifidus and Ceratolithoides aculeus. The Upper Cretaceous ends with a thick upper Maastrichtian succession enclosing significant foraminifers and calcareous nannofossils species. [ABSTRACT FROM AUTHOR]