关键词: 南海, 主量元素, 化学风化, 生产力, 气候记录

Abstract: Some of the major and trace elements in marine sediments are closely related to the source area of sediments. The change of major and trace elemental ratio is affected by chemical weathering intensity in the source area. Therefore, the ratios can reflect paleoclimate change in the source area of marine sediments. In this work, we studied the major and trace elements of the sediments between Marine Isotope Stage (MIS) 6 and 5 in the core of MD12-3432 on the northern slope of the South China Sea. The elemental contents showed good climate control characteristics, with K/Ti, Mg/Ti, Al/Ti, Fe/Ti, Co/Ti, Zn/Ti and V/Ti ratios higher in MIS5 but lower in MIS6. The detrital materials in the northern South China Sea mainly came from southern China. The changes of elemental ratios in sediments showed increased chemical weathering of continental crusts in southern China during the interglacial period (MIS5), indicating warm and humid climate in the South China continent during this period, possibly a result of enhanced East Asian summer monsoon during the interglacial period. The chemical weathering of the source area in northern South China Sea weakened during the glacial period, in contrast to the strong East Asian winter monsoon and cold and dry climate in southern China. At the same time, the Ba/Ti ratio related to surface seawater productivity is higher in the interglacial and lower in the glacial periods, reflecting higher surface productivity during the interglacial period and relatively lower surface productivity during the glacial period in the northern part of the South China Sea. This may be due to increased surface productivity in the northern South China Sea, as increasing East Asian summer monsoon can bring more rainfall which may lead to enhanced chemical weathering on land and large amount of nutrients entering the South China Sea through river channels.

Key words: South China Sea, major elements, chemical weathering, productivity, climate record