Biological markers and their carbon isotopes as an approach to the paleoenvironmental reconstruction of Nansha area, South China Sea, during the last 30 ka

Abstract

Paleoenvironmental changes over the last 30 ka have been documented for the Nansha area, South China Sea, from the biomarkers and their carbon isotopic composition of 314 sediment samples from core 17962. The concentrations of marine lipids indicate that the paleoceanographic and paleoclimatic conditions were not stable in the Nansha area during the last glacial period. The accumulation rates of C 37 alkenones and C 30 alkyl diols show that marine paleoproductivity was higher during the last glaciation than in the Holocene, and correlate well with those of terrestrial biomarkers. Simultaneous variations in accumulation rates of marine biomarkers and terrigenous long-chain compounds during the last glacial period suggest that this enhancement of marine productivity was caused by an increase in terrestrial nutrient supply from the Sunda Shelf. The stable carbon isotopic composition of terrigenous long-chain compounds, such as n-alkanes ( δ 13C=−28.6∼−34.2‰), n-alkanoic acids ( δ 13C=−27.1∼−31.8‰) and n-alkanols ( δ 13C=−26.6∼−35.3‰), indicates that these compounds were derived from C 3 plants, and the surrounding area of southern South China Sea was not dry during the last glacial.