Stratigraphic scheme for the neogene deposits of the Northern Black sea region and adjacent part of the Ukrainian shield

Abstract

There are currently two stratigraphic schemes (1993 and 1995) utilised for stratigraphic subdivision of the Neogene deposits of the Northern Black Sea region and adjacent parts of the Ukrainian Shield. These schemes are based on biostratigraphic (molluscs, foraminifers, ostracods) and lithological studies and therefore local stratigraphic subdivisions used in these schemes (according to the Stratigraphic Code of Ukraine, 2012) are essentially biostratigraphic subdivisions, namely «beds with fauna». This fact impedes using these stratigraphic schemes as a basis for developing legends for large-scale and medium-scale geological maps. A new modernized stratigraphic scheme of the Neogene deposits of the Northern Black Sea region and adjacent parts of the Ukrainian Shield is introduced in this study. The scheme is supported by new and previously published data on the distribution of lithological types of Neogene sediments and their detailed biostratigraphic analysis. The stratigraphic scheme of the Neogene deposits of the Southern Ukraine (1995) includes regional stratigraphic subdivisions – «horizons» that are subordinate to regional stages. The new scheme suggests using only those horizons that are characterized by mollusc assemblages or other paleontological groups. These assemblages should be typical for different facies of coeval sediments in the most structural-facies zones of the Southern Ukraine. The volume of local stratigraphic subdivisions in previous stratigraphic schemes (1993, 1995) has been revised; their stratigraphic status and names have been emended. New local stratigraphic subdivisions, namely formations, beds and strata, have been identified based on the similarity of lithology and biostratigraphy between Neogene deposits of different investigated areas. The age of those local stratigraphic subdivisions has been determined by key species of different fossil groups. These subdivisions have been correlated with the Neogene regional stages of the Eastern Paratethys. Based on the presence of representative fossil assemblages within some local stratigraphic subdivisions, «beds with fauna» have been introduced. The suggested stratigraphic scheme of the Neogene deposits of the Northern Black Sea region and adjacent parts of the Ukrainian Shield consists of two sheets with a graphic image of the scheme, three graphic appendices and text. Sheets demonstrate the spread areas of local stratigraphic subdivisions, their spatial and stratigraphic correlation and names. Sheet 1 includes a schematic diagram of the Neogene deposits from the west to the east: Western structural-facies zone – Genichesk structural-facies subzone – Priazovye; Sheet 2 – from the south to the north: Genichesk structural-facies subzone – Kakhovka structural-facies subzone – the southern slope of the Ukrainian Shield. The «beds with fauna» have been shown for local subdivisions. The comparison of local stratigraphic subdivisions from this scheme with those from the previous schemes (1993, 1995) is provided in graphic appendices.