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Monsoon Intensity and its Impact on the Chemical Weathering during Glacial Cycle in the South China Sea


The Earth's climate and tectonic systems are considered to be linked and to influence one another, often modulated through surface processes. The classic example of this is the tectonic evolution of Asia after its collision with India and the associated intensification of the Asian summer monsoon. It is widely agreed that the East Asian monsoon plays a key role in controlling local climate change and sediment transportation in SE Asia since the start of the Neogene. Monsoon intensification is also closely linked with rates of physical erosion and chemical weathering of bedrock. Several studies have identified the geochemical and mineralogical variations in sediments accumulating in the Asian marginal seas and that have been related to changes of monsoon intensity in Cenozoic, especially after the Miocene.

However, demonstrating links between climate change and sediment composition and transportation are complicated because of the influence of drainage capture as well as tectonic processes that overprint the climate related changes. It is also poorly understood how monsoon intensity variations during glacial and interglacial cycles have influenced sediment production and transportation over the relatively short time scales. In this study, we hypothesize that more sediments will be delivered to the deep ocean from the Mekong River during glacial time because the continental will be exposed and that this effect is more important than the accelerated erosion caused by a strong summer monsoon during integration times. Site U1433 from Intergrated Ocean Drilling Program 349 was used to provide a high-resolution record of variations in chemical weathering by using geochemical and mineral proxies from sediment cores in the southwestern South China Sea to determine how the sediment were transported.