Quantitative sediment provenance of the northwestern East China Sea: Evidence for tidal current-driven offshore transport and paleogeographic implications

In the northwestern East China Sea, sediment transport and mixing in both along-shelf and cross-shelf di-mensions are distinguished using quantitative provenance analysis, with an aim to demonstrate a net transport pattern and thereby infer potential transport and dispersal processes over geological timescales. The dataset comprises 328 bottom sediment samples, which were characterized by detrital-mineral and grain-size analyses. Results show that only in the south of the study area the primary source of sediment is the Yangtze River. In the north, instead, three end-member sources, i.e., the Yangtze, Yellow and Huaihe Rivers, are quantified separately using an end-member mixing analysis. Along-coast mixing between the updrift Huaihe-Old Yellow and down -drift Yangtze River systems is minimized. In exchange, offshore sediment transport is enhanced instead. This conversion from along-shelf to cross-shelf transport is attributed to the presence of a large-scale radial tidal current system off the Jiangsu coast as well as the headland effect produced by the protruding north flank of the subaerial Yangtze delta and the Yangtze riverine plume. This radial tidal current system acts both as a trap for Huaihe-Old Yellow River sediments transported by the southward-direct longshore current, and as a transfer center for sediment dispersal offshore. Radiating transport pathways virtually indicate an extensive mixing of Yangtze sediments and Old/modern Yellow and Huaihe sediments in the southwestern Yellow and northernmost East China Seas. As an independent dynamic system, it acts as a critical link between the Yangtze and modern/ Huaihe-Old Yellow River dispersal systems. Thus, we conclude that these three large-scale dispersal systems and their complex interplay dominate sediment transport, redistribution and mixing on the eastern China continental shelf.