Multi-proxy sedimentary records in the northeastern South China Sea: Implication for sea level and East Asian Summer Monsoon evolution since 13 ka BP

Climate change, sea level rise, and surface circulation changes can be inferred from the Late Pleistocene sedimentary records in the northern South China Sea (SCS). The high-resolution grain size, clay mineral, and trace element analysis of the core in the northeastern SCS have documented paleoenvironmental changes since 13 ka BP. Clay mineral assemblages and trace element analyses of the core indicate that sediments in the northeastern SCS mainly originated from Taiwan Island since 13 ka BP, with a minor contribution from the Pearl River. Highprecision grain size analysis of the core HX6 reveals the significant influence of the East Asian Summer Monsoon (EASM) and sea-level changes to the sediment source to sink process. Furthermore, extreme climate events and topography also have a significant impact on the occurrence of turbidity current since 13 ka BP. Unmixing grain size analysis of four End-Member components in normal sediment layers using the End-Member Modeling (EMM) suggests an increase in EM1 (0-1.5 mu m) content in the northeastern SCS with rising sea levels. The EM2 (2-10 mu m) and EM3 (6-24 mu m) components are primarily influenced by EASM precipitation and could reflect EASM intensity. Over the past 13 ka BP, EM3 content has shown synchronous variations with numerous paleoclimatic records in southern China and the July 25 degrees N insolation intensity. EM4 (10-100 mu m), representing coarse sediment fractions, is influenced by El Nino-Southern Oscillation (ENSO) and abnormal warming in the Indo-Pacific Warm Pool (IPWP). Our findings further demonstrate that the synchronous evolution of EASM in South China was primarily driven by northern hemisphere summer insolation.