Sedimentary budget of the Northwest Sub-basin, South China Sea: controlling factors and geological implications

摘要

We calculated the sedimentary budget of the Northwest Sub-basin (NWSB), South China Sea for different geological times based on interpretations of four multichannel seismic profiles across the basin with constraints from International Ocean Discovery Program (IODP) Expeditions 367 and 368 drilling results. Sedimentation was generally dominated by regional tectonic events and climate change, but complicated by local tectonic events and geographic position, which resulted in a specific sedimentary budget in the NWSB compared with other marginal basins and the Southwest Sub-basin. The sedimentation rate was relatively low following the opening of the NWSB but increased gradually during the Middle Miocene, corresponding to the uplift of the Tibetan Plateau and the Asian monsoon. It reached its peak in the Late Miocene, corresponding to uplift of the Dongsha Island region that caused intensive bypass of eroded sediments from the Baiyun Sag into the abyssal basin, and reduced again during the Pliocene because of sediment storage on the wide northern continental shelf area compared to the abyssal basin during a period of high-stand sea level. Increase in sedimentation during the Pleistocene suggests that continental erosion and sediment transport to the abyssal basin were enhanced by an intensified Asian summer monsoon and glacial-interglacial climate fluctuations. Since the opening of the NWSB, the primary sediment provenance has been from southern China, with minor contributions from the Red River, Hainan Island, as well as local uplifts on the continental shelf.