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In this paper, it is proposed that the formation of eastern Mediterranean sapropels occurred in an anti-estuarine type of circulation, which was to some degree weakened relative to the present in response to reduction of the eastern Mediterranean excess of evaporation over freshwater input. This reduction of excess evaporation would have been imposed by intensifications of (1) the Indian Ocean summer (SW) monsoon, influencing the eastern Mediterranean via increased Nile discharge, and (2) the system of Mediterranean depressions (an element of the westerly Atlantic system) causing increased precipitation and decreased evaporation. Both the Indian Ocean summer monsoon, and the westerly Atlantic system, would be intensified in response to the occurrence of distinct minima in the cycle of precession.

It is demonstrated that reduced excess evaporation, whether or not coinciding with global phases of deglaciation, would lead to reduction of surface water salinities in the eastern Mediterranean, causing ’’isolation’’ of previously formed high salinity (cooler) deep water. Thus, mixing was severely reduced, possibly even restricted to eddy diffusion, with only occasional convective events that, because of the existing density gradient, hardly ever would reach the deepest parts of the basin. The consequently diminished oxygen advection down from a few hundred meters in the water column, favoured preservation of the sinking organic matter. This would, however, suffice only to enable the formation of sapropels with low organic carbon contents. The high organic carbon contents observed in various sapropels are argued to reflect superimposed increases of export production.

The described scenario accounts for previously reported (1) increases of organic carbon content with increasing depth of deposition within individual sapropels, and (2) asymmetrical sequences of sapropel deposition, characterized by gradual build-up and rather abrupt ending. It is, furthermore, in agreement with (3) isotopic and faunal reconstructions of the history of exchange transports through both the Strait of Sicily, and the Strait of Gibraltar, and (4) faunal and floral reflections of the presence or absence of a distinct Deep Chlorophyll Maximum with its associated increases in export production, indicating the presence or absence of a shallow pycnocline within the euphotic layer. Moreover, the described scenario (5) is in no way conflicting with the reports of sapropels in the western Mediterranean, and (6) seems to be endorsed by occasionally intercalated intervals suggestive of somewhat improved oxygenation, amisdt anoxic (benthic desert) levels, a situation that has been observed in a few Quaternary and Pliocene sapropels.