PALEOCEANOGRAPHIC AND PALEOCLIMATOLOGIC RECORDS OF THE SEA OF MARMARA DURING THE LAST 70 KA

Abstract:

The Sea of Marmara is located between the Mediterranean and the Black Sea to which it is connected with the İstanbul (Bosporus) and Çanakkale (Dardanelles) straits having sill depths of 35 and 65 m below the present sea level, respectively. It is presently characterized by a two-way flow system consisting of the upper Black Sea and lower Mediterranean waters separated with a permanent halocline at -25 m.

A 28.88 m long RV Marion Dufresne core MD01-2430 from the western high provides a continuous stratigraphic record for the last ca 70 ka. This record shows only one lacustrine-marine transition at ~ 12.6 cal ka BP over this period, indicating that the Sea of Marmara was under lacustrine conditions disconnected from the Mediterranean Sea from the beginning of Marine Isotope Stage 4 (MIS-4) to the early MIS-1. Soon after the reconnection, the Marmara sapropel started depositing under dysoxic-suboxic conditions during 12.33-5.7 cal ka BP.

The periods of high inorganic (carbonate) and organic carbon production and burial in the Sea of Marmara correlate very closely with the Greenland Intertadials (GI) recorded in the NGRIP oxygen isotope and Black Sea Ca data sets. The two partly overlapping Ca peaks in the Sea of Marmara record corresponding to ~12.6 cal ka BP and 14.5 cal ka BP represent the authigenic carbonate deposition that resulted from the mixing of lacustrine Marmara and saline Mediterranean waters during the latest marine reconnection and the Greenland Interstadial-1 (GI-1) high productivity period, respectively. Low δ¹⁸O (down to -9‰) and high δ¹³C (+2.4‰) values of bulk carbonate during the GIs strongly suggest high input of fresh waters from the Black Sea and high organic productivity in the lacustrine Marmara under warm and humid conditions. Low “carbonate-free” K concentrations during the GIs suggest low detrital input in the Marmara “Lake”, which in turn indicates low erosion rates in the catchment with a high vegetation density. In contrast, the highest detrital input occurred during the Last Glacial Maximum (LGM) and deglaciation (22-15 ka BP) under cold-dry and low lake level conditions.