Abstract
The source-to-sink system of the northern South China Sea (SCS) has been widely discussed during the past few decades. Sr–Nd isotope, clay minerals and trace elements were extensively used as the proxies of sediment provenance, however, still little is known about the transport processes and controlling mechanisms on detailed spatiotemporal scales due to the limitations of these methods. Here we put forward the new provenance proxies RAK and RKCN based on major element compositions to study the spatiotemporal changes in sediment provenance since 150 ka mainly from four sites, DLW3101, MD12-3429, ZHS-176 and MD12-3432, which are located on the northern SCS continental slope. Our results show that, spatially, the pathways and intensities of contour currents and gravity flows play important roles in sediment transport. For alongslope processes, the South China Sea Branch of Kuroshio Current (SCSBKC) and the Deep Water Current (DWC) transport sediments from southwestern Taiwan, while the Intermediate Water Current (IWC) can carry sediments from Hainan, the Red River or the Indochina Peninsula. For downslope processes, gravity flows transport materials from the Pearl River delta and shelf to the slope. Moreover, seafloor bathymetry influences sediment transport by altering the pathways of ocean currents. Temporally, the impacts of sea level and monsoon rainfall fluctuations are always superimposed over the last 150 ka. Sea level fluctuations could significantly change the distance from the Pearl River estuary to the slope, while variations in the East Asian summer monsoon (EASM) rainfall would affect continental erosion rates in the source regions.
Highlights
The South China Sea (SCS) is an excellent case setting for fluvial sediment source-to-sink transport process studies (Liu et al 2016)
4.1 Major element compositions Major element compositions at sites DLW3101, MD123429 and MD12-3432 vary on glacial–interglacial cycles
5.1 Proxies of sediment provenance The sediment provenance proxies we proposed here are RAK and RKCN, which are derived by the chemical index of alteration (CIA) based on major element contents
Summary
The South China Sea (SCS) is an excellent case setting for fluvial sediment source-to-sink transport process studies (Liu et al 2016). The Pearl River contributes approximately 80 Mt/a of fluvial sediments to the SCS (Fig. 1) Southwestern Taiwan supplies ~ 70 Mt/a sediments to the northern SCS (Fig. 1) (Milliman and Farnsworth 2011), transported westwards by contour currents (Wan et al 2010a; Hu et al 2016; Liu et al 2017). The various source-to-sink processes contribute to different clay mineralogical and geochemical characteristics, due to the diverse material compositions of the fluvial sediments around the SCS (Liu et al 2016). Clay mineralogical and geochemical proxies of the east Asian summer monsoon evolution in the South
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