Magnetic characteristics of sediments from the central basin of the South China Sea since the late Pleistocene: Implications for sediments provenance and evolution of the East Asian monsoon

The sediments of the South China Sea (SCS) record abundant information on plateau uplift denudation, paleo-oceanic, East Asian monsoon and regional tectonic evolution, and are ideal material for the study of the East Asian monsoon and paleoenvironmental evolution. However, the complex sedimentary environment and provenance in the SCS make it more difficult to date the sediment and investigate the environmental evolution. Therefore, in this paper, we select the core SCS-01 sediment from the central basin of the SCS to establish the accurate chronological framework, and then use a combination of magnetic and geochemical methods to explore the sediments provenance and their indications for the evolution of the East Asian monsoon. The magnetic characteristics of the sediment reveals that the dominant magnetic mineral is Pseudosingle Domain (PSD) magnetite with low coercivity, uniform particle size and low variation in content, which basically meets the "homogeneity" criterion for establishing the Relative Paleointensity (RPI) curve of the geomagnetic field. Then, RPI is obtained by normalizing the Natural Remanence Magnetization (NRM) using magnetic susceptibility (Z) and Anhysteretic Remanent Magnetism (ARM). We compared the RPI curve with the global or regional standard RPI curves (Sint-200, NAPIS-75 and SCS-PIS) to obtain 6 age control points, and combined with AMS-C-14 dating results to reconstruct a reliable chronological framework since 75 ka for the central basin of the SCS. The consistency of RPI records between SCS-01 and other global observations indicates that the global scale geomagnetic paleointensity model is also recorded in sediments of SCS. Finally, the magnetic information and the rare earth elements results indicate that the sediments of core SCS-01 are mainly from the Taiwan region, with a small amount from the Luzon Island, which is significant for the further comprehensive understanding of the sediment provenance distribution in various regions of the SCS. In addition, the environmental magnetic records of core SCS-01 can reflect the changes of the East Asian monsoon during the glacial-interglacial period since 75 ka, providing a reliable indicator of climate change on the millennial scale in this area.