동해의 동위원소 기간 6의 추웠던 지구화학적 기록

Abstract

Stable oxygen isotope of foraminifera and alkenones variation of the two piston core (MB96EBP-4 and M04-PC1A) were conducted to elucidate the evolution of paleoceanography of the East Sea (Japan Sea). Paleoenvironmental changes since the last ~ 320 ka was reconstructed based on the oxygen isotope compositions of forminifera and alkenons data from the deep-sea sediments of the piston core taken from the Korea Plateau in the East Sea (Japan Sea). Oxygen isotopic records of the planktonic foraminifera, that were estimated to be ca. 320 ka in age, show the Marine Isotope Stage (MIS) from 1 to 8. Comparing this result with previously reported stable isotope data in the East Sea as well as the global oxygen isotope trend, it is suggested that paleoceanographic and paleoclimatic changes in the East Sea has been quite different from those of open oceans: it reserves freshwater input signals and steep drop of paleotemperature (about 2 per mil heavier) at the MIS 2.1 and 6.2, respectively. Paleotemperature variations of the surface water in the East Sea were reconstructed using unsaturated longchain alkenones (ULA) along with oxygen isotope data. The result shows that paleotemperature was about 10oC lower than today’s surface temperature during the MIS 6.2. However, paleotemperature during the MIS 2.2 was characterized by relatively small temperature drop of about 3~4 oC. Both oxygen isotope and ULA data show the systematic coeval trend throughout the late Quarternary. The two core data suggesting local oceanographic condition were more distinctive feature and have prevailed since the MIS 6 in the East Sea.