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

Abstract

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 Sl from ∼9500–6000 (uncorrected radiocarbon convention years B.P.) in the rapidly accumulated sediments and ∼9500–5300 years B.P. in the slowly accumulated sediments. This difference is ascribed to bioturbation affecting the slower accumulated Sl sediments. In the two most rapidly accumulated Sl 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 Sl 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.