Towards Quantitative Determination of Time Series Contribution of Detrital Sediments to the Northeastern South China Sea Since 28.5 kyr BP

High-resolution clay mineral components were analyzed at Core MD05-2905 (20°08.17‧N, 117°20.61‧E, water depth 1647 m), which is located on a high sedimentation-rate sediment drift in the northern South China Sea in order to determine terrigenous sediment provenance and its variations in quantitative contributions over the past 28.5 kyr. The X-ray diffraction (XRD) technique was used to generate relative percentages of four major clay mineral species. The results shows that the clay mineral assemblage consists of dominant illite (42% on average, similarly hereinafter), moderate chlorite (27%) and smectite (23%), and rare kaolinite (8%). Combined with previous investigations on surface samples from the study region and surrounding continents, our provenance analysis reveals three characteristic end-member sources: south Taiwan, Luzon Islands, and the Pearl River. By adopting illite crystallinity index, a quantitative determination method has been constructed to study time series terrigenous contribution variations. We found that a large portion of terrigenous clastic sediments derives from south Taiwan with its contribution more than a half of total fine-graind sediment budget of the sediment drift body. In contrast, contributions from Luzon and the Pearl River varies oppositely, showing a shift from the Pearl River-dominanted materials during the deglaciation to the increased contribution from Luzon Islands during early to middle Holocene. We suggest that the Luzon contribution may relate to the Kuroshio Current intrusion intensity through the Luzon Strait to the South China Sea. Such the intrusion weakened significantly during the H1 event at around 16 kyr BP. The variation in the Pearl River contribution is likely affected by the southward shift of summer intertropical convergence zone (ITCZ), which carries pontential rainfall on exposed shelf leading to the strenghtened physical erosion.