EVOLUTION OF THE TSUSHIMA WARM CURRENT DURING THE HOLOCENE: SEDIMENTOLOGICAL AND GEOCHEMICAL RECORDS ON THE SOUTHWESTERN SLOPE OF EAST/JAPAN SEA

Synthetic analyses on sedimentology and geochemistry of a sediment core with high deposition rate collected under the Tsushima Warm Current (TWC) axis on the southwestern slope of East/Japan Sea were carried out, in order to discuss the formation and evolution of TWC during the Holocene. Based on them, we got very similar results to those from paleoceanographical method in nearby areas. Thus, sedimentological and geochemical methods were offered for the future study on TWC evolution in the study area. Totally, there were five main evolution periods of TWC recorded in the study core. In the early Holocene, that is 9.6 kaBP, TWC began to weakly enter into the East/Japan Sea, together with the East China Sea Coast Water (ECSCW) enriched in nutrient matter, which led to the transfer of bottom environment from anoxic to oxic. At 6.5 kaBP, the modern current mode dominated by TWC in the southern East/Japan Sea finally formed, whereas the influence of ECSCW almost disappeared. After that, TWC obviously weakened. At 3.0 kaBP, TWC strengthened again to almost reach its present level, since then the circulation structure has been relatively stable, except for a weak depression of TWC during 2.0~0.7 kaBP.