The last sea level changes in the Black Sea: Evidence from the seismic data

High resolution shallow seismic data collected from the southwestern shelf of the Black Sea indicate five different seismic stratigraphical units. The lower three of them belong to the Upper Cretaceous-Eocene, Oligocene-Miocene and Early Quaternary (prior to Holocene) sediments, respectively. These units are considered as a basement for the recent sediments deposited related to the latest connection of the Black Sea and the Mediterranean. The surface of these units are truncated to form an etchplain developed before the Flandrian transgression. The fourth unit covers the older units by an onlap. Its contact with the older units seen at - 105 m is the shoreline of the Black Sea prior to the last major sea-level change. The fifth unit has been deposited since drowning of the Black Sea shelf. The principal cause of drowning of the Black Sea shelf is not only the last sea level rise as it is at the shelves of the Sea of Marmara but also the opening of the Strait of Istanbul. It is also realised by the comparison of the shelf area and the Catalca-Kocaeli etchplain that, the present continental part of this etchplain has been considerably uplifted with respect to the shelf area along the present shoreline. This uplifting must have also reactivated the faults around the Strait of Istanbul foundering the strait valley and, thus, permitting the Mediterranean waters to pass into the Black Sea, and initiating the sudden drowning of the Black Sea shelf.