Molecular biomarker record of sea surface temperature and climatic change in the South China Sea during the last 140,000 years

Abstract

The δ 18O and δ 18C isotopic composition of Globigerinoides ruber, the concentration of C 37 alkenones, n-nonacosane and n-hexacosan-1-ol and the populations of coccolith species in core 17961-2 have been used to characterize the climatic changes which occurred in the South China Sea (SCS) during the last climatic cycle. The relative composition of di- and triunsaturated C 37 alkenones, the U 37 K index, has been used to estimate the variation in sea surface temperatures. The concentrations of the terrigenous markers n-nonacosane and n-hexacosan-1-ol have allowed to infer changes in continental water dynamics during the glacial and interglacial times. The stratigraphic record of these compounds has shown that the influence of continental waters (i.e., the Molengraaff River) and restricted water circulation in SCS gave rise to a marginal system of higher but slower response to climatic change. Both in terminations I and II, the change from glacial to interglacial conditions involves a considerable reduction of continental water input into this semi-enclosed system. The high resolution study of the biomarker proxies in Termination I has shown that the SST increase lagged about 2.3 ky the δ 18O isotopic decrease of Cibicidoides wuellerstorfi. Probably, the SST increase corresponds to the period of the Sunda Shelf inundation onset.