동해에서 과거 40만년간 고해양 및 고기후 진화

Abstract

Geochemical proxies of stable oxygen isotope of foraminifera, carbon and nitrogen isotope of organic matter, and total organic carbon (TOC) and inorganic carbonate content of a piston core taken from the East Sea (Japan Sea) were investigated to understand the paleoceanographic and paleoclimatological evolution since the last 400 kyr. Oxygen isotope signals of foraminifera shows large fluctuation, ranging from MIS (Marine Isotope Stage) 1 to MIS 11 with a distinctive glacial-interglacial variation. Comparison of oxygen isotopic record for glacial and interglacial conditions during the 400 kyr reveals that paleoceanographic and paleoclimatic changes in the East Sea is quite different from those of open oceans. Unlike the previously reported global paleoceanographic data, the oxygen isotope data during the MIS 2, 6, and 8 consistently show depleted signatures, indicative of surface-water freshening. The content of biogenic carbonate, TOC and carbon and nitrogen isotope of organic matter (δ13C and δ15N) were determined and C/N ratio of the organic matters was used to interpret paleoenvironmental changes during glacial and interglacial periods. In studied core, the content of TOC and biogenic carbonate showed large fluctuation between glacial and interglacial periods. Based on the C/N ratio and the isotopic composition of δ13C and δ15N, which showed extreme temporal variation since MIS