Oscillating Quaternary water levels of the Marmara Sea and vigorous outflow into the Aegean Sea from the Marmara Sea Black Sea drainage corridor

Detailed interpretation of single-channel air-gun and deep-tow boomer profi les demonstrates that the Marmara Sea, Turkey, experienced small-amplitude (similar to 70 m) fluctuations in sea level during the later Quaternary, li mited in magnitude by the sill depth of the Strait of Dardanelles. Moderate subsidence along the southern shelf and Quaternary glacio-eustatic sea-lev el variations created several stacked deltaic successions, separated by maj or shelf-crossing unconformities, which developed during the transitions fr om global glacial to integlacial periods. Near the Strait of Dardanelles, a series of sand-prone deposits are identified beneath an uppermost (Holocen e) transparent mud drape. The sandy deposits thicken into mounds with the m orphology and cross-sectional geometries of barrier islands, sand waves, an d current-generated marine bars. All cross-stratification indicates unidire ctional flow towards the Dardanelles prior to the deposition of the transpa rent drape which began similar to 7000 years BP, in strong support: of the notion that the Marmara Sea flowed westwards into the Aegean Sea through th e Dardanelles at times of deglaciation in northern Europe. The global sea-l evel curve shows that, at similar to 11,000 and similar to 9500 years BP, s ea level rose to the sill depths of the Straits of Dardanelles and Bosphoru s, respectively. The effect from similar to 11,000 to similar to 9500 years BP was seawater incursion into the Marmara Sea, drowning and formation of algal-serpulid bioherms atop lowstand barrier islands, and transgression of shelves and lowstand deltas. At similar to 9500 years BP, glacial meltwate r temporarily stored in the Black Sea lake, developed into a vigorous south ward flow toward the Aegean Sea, forming west-directed sandy bedforms in th e western Marmara Sea and initiating deposition of sapropel S1 in the Aegea n Sea. This strong outflow persisted until similar to 7000 years BP, after which a mud drape began to accumulate in the Marmara Sea and euryhaline Med iterranean mollusks successfully migrated into a progressively more saline Black Sea where sapropel deposition began. Most eastern Mediterranean sapro pels from S1 to S11 appear to correlate with periods of rising sea level an d breaching, or near-breaching, of the Bosphorus sill. These events are bel ieved to coincide with times of vigorous outflow of low-salinity (?fresh) s urface waters transiting the Black Sea-Marmara Sea corridor, and ultimately derived from melting of northern European ice sheets. (C) 1999 Elsevier Sc ience B.V. All rights reserved.