HIGH-RESOLUTION RECORDS OF BIOGENIC COMPONENTS AND THEIR PALEOCEANOGRAPHIC IMPLICATIONS IN THE UPWELLING AREA OF THE SOUTH CHINA SEA OFF EASTERN VIETNAM OVER PAST 480 ka

Based on the study of sediment samples from core MD05-2901 which is in the upwelling area in the South China Sea off eastern Vietnam, we obtained high-resolution records of biogenic components over the past 480 000 years. The records provide us paleoproductivity and paleoceanographic information associated with East Asian monsoon system. There were high total organic carbon (TOC) and high biogenic opal content during the glacial periods, and low TOC and low biogenic opal content occurred during interglacial periods. This indicates the intensified terrigenous sediment input during glacial periods, which is due to the low sea level. Particularly, both the TOC and biogenic opal content reached their maximum values during the last glacial period, which shows high productivity in this area caused by the strong northeast wind during the last glacial maximum (LGM). The variation of carbonate concentration displayed opposite trend to TOC and opal, and high value occurred during the deglaciation periods, indicating that CaCO₃ cycle in this area was influenced by terrigenous dilution and the effect of "Carbonate pump" caused the high CaCO₃ content during deglaciation periods. Moreover, the variations in paleoproductivity proxies exhibit a distinct cyclicity with a frequency of nearly 23 000 years, mainly responding to precession cycles, suggesting an influence of low latitude process, such as the monsoon climate in the South China Sea.