PLANKTONIC FORAMINIFERA IN THE XISHA TROUGH OF THE SOUTH CHINA SEA DURING THE LAST 120 KA AND THEIR PALEOCLIMATIC IMPLICATIONS

Planktonic foraminifera from the core 83PC in the Xisha Trough of the northern South China Sea (SCS) have been quantitatively analyzed. The microfaunal analytical results, combined with oxygen and carbon isotopes, carbonate content and AMS¹⁴C dating data, are used in this paper to reveal paleoceanographic characteristics of the study area during the last~120 ka. The distribution of planktonic foraminifera shows that the abundance decreased in glacial periods, warm water species were sensitive to temperature changes, and the percentages of cool water species have decreased gradually since MIS5. Sea surface paleotemperature (SST) was estimated via transfer function FP-12E. The calculation results suggest that the winter SST ranged from 21.3 to 26.4℃, the summer SST from 28.2 to 29.5℃, and the SST seasonality from 2.7 to 6.9℃. By comparison with the results from the southern SCS, the SST differences were evident from MIS2 to MIS5, which probably resulted from the growth of the Northern Hemisphere ice sheet and the strong East Asian Monsoon, the higher SST differences in glacial periods indicated enhanced winter monsoon. Several obvious short-term SST descending events, including the Younger Dryas and Heinrich events, have been recognized since the last glaciation, suggesting the sedimentary records in response to the global climatic changes in the SCS.