Organic carbon distribution and isotopic composition in three records from the eastern Mediterranean Sea during the Holocene

International audienceWe investigated the distribution of organic carbon (TOC) and bulk organic δ 13C org values in two cores from the Aegean Sea and one from the Libyan Sea, eastern Mediterranean Sea (EMS) with a focus on the timing and regional expression of sapropel S 1 deposition in the early Holocene. Our data indicate that the onset of S 1 occurred earlier in the Libyan Sea (∼9.8 kyr BP) than in the Aegean Sea (∼8.9 kyr BP), implying that dysoxia/anoxia started earlier in the deeper sites of the EMS than in the shallower sites in the Aegean Sea. Accumulation rates of organic matter (OM) during the S 1 period have a clear decreasing gradient from north to south, with higher values in the Aegean Sea and TOC contents higher in the deep basin. The three sedimentary sequences exhibit δ 13C org values that fall within the range of algal OM (-25‰ to -20‰). Shifts to lighter δ 13C org values within sapropel intervals in the Aegean sites can be interpreted as the result of elevated marine production, enhanced inflow of light terrestrial dissolved inorganic carbon and/or of the shoaling of the pycnocline, along with the presence of a deep chlorophyll maximum (DCM) during the S 1 period