Duration of S1, the most recent sapropel in the eastern Mediterranean Sea, as indicated by accelerator mass spectrometry radiocarbon and geochemical evidence

Slowly accumulated (<5 cm kyr(-1)) and rapidly accumulated (5-20 cm kyr(-1)) sediments have been compared to define the initiation and termination times of the most recent sapropel (S1) in the eastern Mediterranean Sea. The Ba/Al ratio has been employed as a more persistent index of productivity than C-org. Accelerator mass spectrometry radiocarbon dating of pelagic foraminifera indicates a maximum duration for increased Ba/Al levels in S1 from similar to 9500-6000 (uncorrected radiocarbon convention years B.P.) in the rapidly accumulated sediments and similar to 9500-5300 years B.P. in the slowly accumulated sediments. This difference is ascribed to bioturbation affecting the slaver accumulated S1 sediments. In the two most rapidly accumulated S1 units, from the Adriatic and Aegean Seas, there is a "saddle" of lower values centered on 7500 years B.P. in the C-org and Ba/Al profiles, so that the visual S1 unit appears as a doublet. Geochemical evidence indicates that this intervening period is best interpreted as an episode of increased ventilation and bottom water oxygenation during the period of sapropel accumulation.