Organic molecular and carbon isotopic records of the Japan Sea over the past 30 kyr

The organic and isotopic geochemical study of two sediment cores (KH-79-3, L-3, and KH-79-3, C-3) from the Oki Ridge in the Japan Sea has revealed tha t total organic carbon (TOC) mass accumulation rates are extremely high in the 12-11 ka(calendar age) interval and TOC in the sections in the 24-17 ka interval is depleted in C-13 by 3.5 parts per thousand relative to Holocen e sediments. Alkenone sea surface temperature (SST) shows a decrease from 1 8 degrees to 14 degrees C from 17.5 to 11.6 ka and a sharp increase from 14 degrees to 19 degrees C from 11.6 to 11.1 ka. The SST changes are associat ed with the inflow of cold seawater with the vertical water mixing and the inflow of warm Tsushima Current into the Japan Sea. The delta(13)C values f or both 24-methylcholesta-5,22-dien-3 beta-ol (diatom marker) and dinostero l (dinoflagellate marker), are at their minimum from 24 to 17 ka, while tho se for long-chain alkenones are not. The theoretical considerations on delt a(13)C for biomarkers suggest low photosynthetic carbon demand of diatoms a nd dinoflagellates from 24 to 17 ka.