LOW CARBONATE EVENT IN NORTHERN SOUTH CHINA SEA DURING THE EARLY HOLOCENE AND THEIR PALEOCLIMATIC SIGNIFICANCE
Li Xuejie 1,2 Jiang Maosheng3 1Institute of Development Strategics for Marine Geoscience,Guangzhou Marine Geological Survey,Guangzhou 510760,Guangdong 2Laboratory of Marine Geology,Tongji University,Shanghai 200092 3Institute of Geology and Geophysics,Chinese Academy of Science,Beijing 100029
Carbonate cycle,which is controlled by sea surface productivity,dilution of terrigenous sediment and dissolution of deep-sea,is the most prominent feature in South China Sea since Late Pleistocene. In the northern South China Sea,variations of carbonate content are mainly controlled by dilution of terrigenous sediment. More terrigenous sediments were transported into the deep-sea areas through continental shelves (dilution cycles) during sea-level lowstand period. Studies on the cores from the northern slope of Xisha Trough show a high carbonate content during deglaciation (sea-level highstand period) and a rapid decrease in carbonate content (the low carbonate event) during early-middle post-glacial period (sea-level lowstand period,6～8 ka BP). This low carbonate event may have resulted from changes of rainfall. During deglaciation,the dry climate caused a decrease in terrigenous sediment input. However,during Early-Middle Holocene,the rainfall,especially the heavy rain with higher erosions increased rapidly,leading to the increase of terrigenous sedimental supplies from South China mainland and Hainan islands.