Reconstruction of paleohydrological and paleoenvironmental changes using organic carbon and biomarker analyses of sediments from the northern East China Sea

摘要

Paleohydrological and paleoenvironmental changes were reconstructed using sedimentary records from the northern East China Sea, representing the past 15,000 years (from the last glacial period to the Holocene). The n-alkane distributions show many factors, from the changing origins (plant types) of organic matter input to marine sediments. Two climatic conditions were distinguished (warm/humid and cold/dry) by comparing the organic carbon isotope ratio (δ~(13)C_(org)) with the reported planktonic foraminiferal oxygen isotope ratio (δ~(18)O) of Clobigerinoides ruber. A shift in the n-alkane-specific δ~(13)C values reveals that the hydrological changes in the northern East China Sea were related to the carbon sources for aquatic macrophytes. The alkenone sea surface temperatures [SSTs (U~K'_(37))] record of the 07YSPC12 shows a range of 20.3 ℃-26.5 ℃ (average 22.9 ℃). Lower temperature SSTs were recorded during the Younger Dryas, with an average of 21.7 ℃. The variation in the alkenone SSTs is interpreted to indicate the environmental conditions of the growth of alkenone synthesized organisms.