Sea level change and Kuroshio intrusion dominated Taiwan sediment source-to-sink processes in the northeastern South China Sea over the past 244 kyrs

The terrigenous sediment source-to-sink processes in continental margins are determined by complex interactions among climate, sediment discharge, sea level and oceanic circulations on various temporal and spatial scales. The northeastern South China Sea (NSCS) margin is a natural laboratory to catch a glimpse of these processes due to large amounts of terrigenous sediment inputs and continuous sedimentations during the late Quaternary. Based on a 35 m-long sedimentary sequence (core MD12-3429) retrieved from the NSCS upper continental slope, we distinguished sediment sources based on geochemical compositions, and then linked sedimentary responses to sea level change and Kuroshio intrusion over the past 244 kyrs via various sedimentary records including mass accumulation rates (MAR), foraminifera data, grain-size end-member modeling (EMM) and spectral analysis. Geochemical proxies including major element ratios and fractionation parameters of rare earth elements suggest that the detrital sediment in the core was derived primarily from the Taiwan. The MAR of terrigenous sediment yields an average 9.6 g/cm2/kyr, and high MAR values are both observed in glacial and interglacial intervals. The results of EMM reveal three end-members with dominant modal grain sizes of 6.6 μm (EM1), 26.3 μm (EM2) and 49 μm (EM3), respectively. The temporal variations of the finest end-member (EM1) and the coarsest end-member (EM3) demonstrate clearly glacial-interglacial cyclicity, and the spectral analysis indicates the dominance of 100-kyr eccentricity, which suggests that sea level changes are the first-order control for the NSCS continental margin sedimentation. In addition, the temporal variations in hydrodynamic sensitive component (EM2) and its MAR display gradually increasing trends with weakening East Asian monsoon. Combing with modern observation and modeling results, we suggest that enhanced Kuroshio intrusion might account for the transport of Taiwan-derived sediment during the late Quaternary. As indicated by a 31 kyr periodicity in EM2, we infer that the development of El Niño-like condition strengthened the intrusion of oligotrophic Kuroshio from the Luzon Strait, resulting in the obvious increase of Taiwan terrigenous MAR but decreases of the primary productivity in the northeastern South China Sea. This study provides deep insight into the complex terrigenous sediment source-to-sink processes in a fast-changing marginal sea environment during the late Quaternary.