LAST GLACIAL-HOLOCENE PALEOENVIRONMENT OF THE BLACK SEA EVIDENCED BY SEQUENCE STRATIGRAPHY CORRELATED TO CORE ANALYSIS AND DATING

The Black Sea is the world largest anoxic basin. During the last glacial period it was a low salinity oxygenated lake isolated from the Mediterranean. Its location between Europe and Asia implies that its water level depends on the Eurasian climatic fluctuations. During glacial periods, the Black Sea was isolated from the Global Ocean and was more sensitive to climate changes as the Caspian Sea which provides today a perfect paleoclimate archives. The Black Sea avoids the hysteresis effect corresponding to the latent period for which the Global Ocean has to respond to the melting of the ice. During glacial period, while the Black Sea was disconnected to the Global Ocean (Mediterranean Sea), both the lack of saltwater and the increase of fresh water run off from the rivers, led to a decrease in the salinity of the Black Sea. This behaviour linked to water level fluctuation is measured in the fauna succession showing a brutal change from salt to fresh/brackish species. Since 1997, there is an unsolved controversy concerning the last connection of the Black Sea with the Marmara Sea. This question is still under debate as the Black Sea was not totally surveyed using modern technology. Recently the assessment of the North-western part of the Black Sea sedimentary systems, including the continental shelf and slope down to the deep sea zone, was provided by the ASSEMBLAGE European Project (EVK3-CT-2002-00090). We present here a part of this project deliverables which consist in correlating mapped seismic sequences dated to sea level fluctuations onward long piston core acquisition. We demonstrate that the sedimentary sequences in the Black Sea are strongly affected by water level changes. The level of the Black Sea was linked to the regional climate modifications rather than the global eustatic changes. During the Last Glacial Maximum, the Black Sea was an enclosed lake which the water level was below -120 m depth. The deglaciation raised the lake level up to -30 m. After the Younger Dryas and between 11 till 8.5 kyr 14C BP, the lake level lowered once again down to the level of -100 m depth. It created a pronounced shoreline with a characteristic beach profile and a belt of coastal dunes. These coastal features as well as the incised anastomosed channel system were preserved on the shelf as a result of the fast enough last transgression starting just after 8.5 kyr 14C BP.