Key reflecting horizons in sedimentary fill seismic records of the Black Sea basin (correlation and stratigraphic position)

The seismic CMP is the main method of the geological sections study in the Black Sea, because drilling data on the deep basin part are scarce. Accordingly, stratigraphic subdivisions of sedimentary cover can be defined and correlated here based on key reflecting horizons. In the seismic record of Cenozoic sediments, four key reflecting horizons are distinguished at the base of the Quaternary (C), at the base of the upper Miocene, (I) at the top of the lower Miocene (Ia), and at the top of the Eocene (IIa). The reflecting horizon at the base of Cenozoic sequence (10-12 km thick) corresponds to the top of the Cretaceous overlain by Paleogene sediments (reference reflecting horizon III) in some areas or represents the eroded Mesozoic surface in the others (unconformity U). The key reflecting horizons divide sedimentary fill of the basin into five large complexes of the Quaternary, upper Miocene-Pliocene, middle Miocene, Oligocene-lower Miocene (Maikop Group), and Paleocene-Eocene. Data enabling a more detailed stratigraphic subdivision of sedimentary sequence are unavailable. Mostly simple, almost horizontal attitude of beds well traceable throughout the basin is favorable for correlation of reflecting horizons. All the defined key reflecting horizons and their lateral changes, correlation with onshore and offshore boreholes sections, and some peculiarities in bed attitude are described in detail. It is established that the thickest and most complete Cenozoic section is characteristic of the sea abyssal part, where key reflecting horizons are persistent and perfectly traceable along the strike. After additional study, they can probably be traced to the continental slope and even to the shelf.