PLANKTONIC FORAMINIFERA IN CORE 89PC FROM THE NORTHWESTERN SOUTH CHINA SEA AND THEIR PALEOENVIRONMENT SIGNIFICANCE

Planktonic foraminifera(PF) from core 89PC in the northwest of the South China Sea(SCS) were quantitatively studied. Together with SST and thermocline analysis, PF oxygen-carbon isotopes and calcium carbonate analysis and AMS¹⁴C dating, the fauna revealed major evolutionary paleoceanographic characteristics in the northwest SCS over the last 127 ka. The depth of thermocline showed no obvious fluctuations during MIS5-MIS4, but deepened gradually since MIS3. The sea surface paleotemperature(SST) estimated by the transfer function FP-12E showed that the summer SST ranged from 27.9 to 29.3℃, and the winter SST from 20.6 to 26.3℃. The comparison of SST data between the southern and the northern SCS indicated that SST in southern SCS was higher than that in northern SCS. The SST difference was more obvious in winter. Especially, this difference increased most markedly in the glacial periods, indicating stronger winter monsoon.