Glacial anoxia in the eastern Mediterranean

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Abstract
The development of anoxic conditions and the concomitant deposition of organic-rich facies (sapropels) in the eastern Mediterranean during the last 350,00 yr generally occurred during rapid climatic changes associated with interglacial episodes. An exception to this relationship occurred during O2 isotope stage 6 (195,000-128,000 yr BP) when a sapropel (S-6) was deposited throughout the eastern basin at the height of glacial conditions. Detailed faunal and stable isotopic anlayses of planktonic foraminifera from a core loacted on the Mediterranean Ridge suggest that surface salinites in the eastern Mediterranean were sufficiently reduced during the deposition of S-6 to establish a density inversion in the upper water column. A similar type of density stratification model has been used to explain the origin of the other late Pleistocene sapropels deposited during interglacial times in the eastern basin. During glacial stage 6, lowered sea levels in the Mediterranean would have prevented the flushing of fresh water from the Black Sea by saline Mediterranean water. If the Black Sea were the source of the fresh water input during stage 6, a marine spillway must have existed between the Black Sea and the Mediterranean at this time.