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

We investigated the distribution of organic carbon (TOC) and bulk organic δ13Corg 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 S1 deposition in the early Holocene. Our data indicate that the onset of S1 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 S1 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 δ13Corg values that fall within the range of algal OM (−25‰ to −20‰). Shifts to lighter δ13Corg 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 S1 period.