동아시아몬순에 의한 고기후, 고해양환경 변화

Abstract

Korea Ocean Research & Development Institute (KORDI) develops on three year research program since 2004 which titled on East Asia Monsoon evolution and paleoclimate changes. The program covers on wide field area through the East Asia including not only East Sea (Sea of Japan) but also from onland lake and caves in Korean peninsula. The program has focused on reconstruction of paleoclimate and paleoceanographic changes from the marine and onland core sediments since late Cenozoic and on paleoclimate numerical model during the mid-Holocene and the Last Glacial Maximum (LGM). Total of 7 piston cores from the East Sea and one cave sediment were collected from East Sea with different water depths from 667m to 2,247m deep and from Sup Cave in Gangwon Province, and have analyzed to each geological, geochemical and paleontological components to reconstruct paleoenvironments and paleoclimatic evolution. The Korea Plateau core sediment in the East Sea can be classified into 7 sedimentary facies, and the lowermost part was composed of the storm-influenced nearshore to shallow marine sediments of middle Miocene in age (12.8 to 13.4 Ma) from the 87Sr/86Sr initial ratio (0.70881 to 0.70886). The presence of these sediments implies that the Korea Plateau has been subsequently subsided 600m into the present deep-sea position since the middle Miocene. Oxygen isotopic records of the p. foraminifera (N. pachyderma) indicate that the pelagic sediments represent the MIS 1 to 8. As previously reported, the consistently depleted oxygen isotope signatures may well indicate several episodes of surface-water freshening. This should result from the isolation of the East Sea basin due to the closure of the shallow straits around the East Sea during the MIS of 2.2 and 6.2. Also, the paleotemperature calculated from unsaturated alkenons index of the Korea Plateau core sediment were much lower during the MIS 6 compared to the present-day by about 10℃. In case of climate model study