GEOCHEMICAL RECORD OF TERRIGENOUS SEDIMENTS FROM THE SEA OF JAPAN SINCE LAST GLACIAL AND ITS RESPONSE TO SEA LEVEL AND CLIMATE CHANGE

We analyzed major, trace, and rare earth element chemistry, and grain sizes for KCES-1 piston core sediments from the Ulleung basin in the Sea of Japan to determine the sediment provenance and factors controlling the composition of the sediments. Based on the stratigraphic age model, a 48 ka record for paleoenvironmental change was retrieved. The results show that, the composition of sediments is dominated by terrigenous matter. In general, the concentrations of major and minor elements(Al, K, Fe, Mg, Na, Ti,Th, Sc, Rb, Sr, Cr, Co, Hf, Zr)are less than average shale. REE total abundances (ΣREE) which are closed to those reported previously for the Yangtze,Yellow River, and Chinese Loess, but are much higher than the upper crust composition of Japan Island, range between 80 and 213 μg/g. Chondrite-normalized REE patterns with distinct negative Eu (0.6~0.8)anomalies and a strong light-REE enrichment were seen throughout the data. Cerium anomaly is not distinct. Elemental ratios and La/Th-Hf discrimination diagram of source rocks show that sediments in the study area mainly originate from upper crust and the parent rocks are feldspar-quartzose. During 11~18 ka, the abundances of major, minor, and rare earth elements are different from those during 0~11 ka and 18~48 ka. The factors controlling the elements distributions are related to sea-level and climate changes. The Chemical Index of Alteration (CIA) (45~61) indicates that the intensity of chemical weathering in the sediment source is weak. The weathering intensity is much higher after 18ka, indicating climate changes from cold and dry to warm and wet conditions. The weathering trend is very similar to global climate change and to the intensity of the East Asian summer monsoon.