Environmental magnetic characteristics and provenance significance of sediments in NW South China Sea since the past 16 ka

As the largest marginal sea in the western Pacific Ocean, South China Sea (SCS) is sensitive to the East Asian monsoon and global climate change. The provenance of SCS sediments remains controversial. We carried out a systematic magnetic analysis on Core SCS-02 from the Qiongdongnan Basin, to trace the origin of sediments. Results show that the magnetic carriers of Core SCS-02 sediment are mainly magnetite and hematite. Since 16 kaBP, the particle size and magnetic mineralogy have shown systematic changes, indicating the change of the sedimentary source-sink process. During 15.5～16 kaBP, the sediments were with higher magnetic susceptibility, coarser grain size, and higher coercivity. The sea level was 100 m below the modern one, and the Yingge Sea was above the ancient sea level. The ancient Red River estuary was closer to the study area, leading to more material transported from the old Red River to the depositional area. During 7.5～15.5 kaBP, sea level rose rapidly, the total content of magnetic minerals decreased, but the relative content of magnetite gradually increased, and the magnetic particles became finer, indicating that the contribution of ancient Pearl River and Taiwan increased with the rise of sea level. Since 7.5 kaBP, the modern land and sea pattern had been formed fundamentally, changes in magnetic mineral composition and particle size stabilized relatively, and the sediments were mainly from the modern Red River and the Pearl River. Therefore, the environmental magnetic parameters are good proxies for the source-sink changes of sediments in the South China Sea, and provide an effective reference for the studies of sea level change and climate evolution.