Geochemical evidence for enhanced productivity during S1 sapropel deposition in the eastern Mediterranean

The geochemistry of the youngest Mediterranean sapropel layer suggests chan ges in productivity and water column oxygen conditions during sapropel depo sition. The Ba-enriched interval is broader than the organic-carbon-rich in terval of this sapropel. We suggest that the Ba-enriched horizon records th e original thickness of the sapropel prior to subsequent partial oxidation. The main carrier of Ba is barite, as microcrystals (0.5-5 mu m) having a m orphology characteristic of marine barite, particularly abundant beneath hi gh productivity regions. Ba concentrations do not change at the sapropel la yer oxidation front and diagenetic barite crystals are absent, thus the Ba- enriched layer reflects original oceanic conditions of increased biological productivity during sapropel deposition and not diagenetic Ba remobilizati on. Paleoredox indicators point to restricted oxygenated bottom water but n ot to fully anoxic conditions. Detrital elements within this layer indicate a lower eolian terrigenous input, enhanced humidity, and increased precipi tation/runoff thus likely higher nutrient supply.