The deep sea records from the ODP Sites 1143 and 1144 in the northern and southern South China Sea (SCS), including foraminiferal δ 18O and δ 13C, Opal% and pollen percentage, reveal that the variations of the east Asian monsoon have been closely correlated with the variations of the Earth’s orbital parameters (eccentricity, obliquity and precession) and the global ice volume on orbital scale. All the monsoonal proxies show strong 100 ka, 41 ka and 23 ka cycles. Although G. ruber δ 13C of Site 1143 is coherent with the ETP (ETP= normalized (eccentricity + obliquity-precession) at eccentricity, obliquity and precession bands, most of the coherent relationship focuses on the precession band, and the other monsoonal proxies are coherent with the ETP only at the precession band, which indicate that precession dominates the Pleistocene tropical climate changes. The phase relationship of the monsoonal proxies with the foraminiferal δ 18O implies that the global ice volume changes have played a significant role in modulating the east Asian monsoon climate, at least dominating the winter monsoon. This forcing mechanism of the east Asian monsoon is apparently different from that of the Indian ocean mon-soon. The variations of the east Asian monsoon at the precession band, at least that of the winter monsoon, have been controlled not only by the sensible heating but also by the latent heating of the surface water in the South China Sea.
TIAN Jun1,2, WANG Pinxian1, CHENG Xinrong1, WANG Rujian1 & SUN Xiangjun1,3 1. State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China
The sediment macro-distribution patterns and their evolutionary characteristics in the South China Sea (SCS) are discussed based on a quantification of the sediment mass from the beginning of seafloor spreading in the Oligocene to the Present. Above the pre-Oligocene base, the total sediment mass for the whole SCS is estimated to be 1.44×1016 t, with the highest average accumulation rate of ～22 g·cm-2·ka-1 in the Oligocene. Having no large abyssal fans but fast accumulation in sedimentary basins on the continental shelf and slope, the SCS shows quite different sedimentary characters not only from the open ocean but also from small backarc basins along the marginal West Pacific, apparently controlled by the coupling between local tectonics and global climate changes.
