PALEOCLIMATIC AND PALEOCEANOGRAPHIC CONDITIONS LEADING TO DEVELOPMENTOF SAPROPEL LAYER SL IN THE AEGEAN SEA

Sapropel S1 occurs as 25-35 cm-thick black, weakly laminated muds in A egean Sea cores. S1 was deposited between 9600 and 6400 yr B.P., durin g a period of isotopically depleted and relatively cool surface waters . Micro-faunal and -floral data indicate a major reduction in surface waters salinity during the deposition of S1, and oxygen isotopic data show a northerly fresh water source. Relatively light delta(13)C(org) and high pollen-spore concentrations in S1 suggest increased influx of terrestrial organic carbon, probably supplied by major rivers drainin g into the northern Aegean Sea. Benthic foraminifera indicate high-nut rient, low oxygen bottom waters for S1, and together with silt-sized h ematite and manganese coatings suggest that during the deposition of S 1 surface sediments were oxic. Visual and XRD evidence of pyrite in S1 , together with enrichments in S, Cu, Zn, As, Ni, Cr and Fe suggest th at subsurface conditions were sufficiently reducing for SO42- reductio n to occur, probably by diffusion from surface oxic into subsurface an oxic sediments. Palynomorphs in S1 show large increases in terrestrial pollen and spores, with the floral assemblage indicating significant influx from northern European rivers, and minor African components ass ociated with increased summer monsoonal rain. Abundance of dinoflagell ates and amorphogen suggests some increase in primary productivity in response to increased influx of humic compounds, however, there is no evidence of upwelling. The clay fraction in S1 shows notable decreases in smectite and kaolinite and reciprocal increases in illite and chlo rite. The combined data suggested that the evolution of S1 in the Aege an Sea largely resulted from stagnation of the surface waters during t he final disintegration of the continental ice sheets, rather than an increase in primary productivity and higher preservation of organic ca rbon on the sea floor.