Holocene evolution of bottom sediment distribution on the continental shelves of the Bohai Sea, Yellow Sea and East China Sea

Abstract

Coastline shifts due to transgression and regression can remodel tidal fields of continental shelves, and this can control transport of sediments and modulate sediment distribution accordingly. Tidal currents have become the dominant hydrodynamic processes on the continental shelves of the Bohai Sea, Yellow Sea and East China Sea (BYECS) since the transgression after the Last Glacial Maximum (LGM). To examine the evolution of the bottom sediment distributions on the continental shelves of the BYECS, we simulated patterns of tides and tidal currents, sediment transport, and bottom sediment types (sand, mud and mixed sediments) for five periods, corresponding to sea level lowstands of 80m, 52m and 30m below present, the Holocene transgression maximum (HTM), and the present. The simulation shows that both sediment transport and shelf sediment distribution patterns were controlled by the strength, type and asymmetry of tidal currents in the BYECS since the LGM. Evolution of shelf sediment distribution patterns occurred in two stages: (1) sediment emplacement and formation stage before the HTM, and (2) local adjustment after the HTM. The marked changes in coastline configuration since the LGM are the dominant factor controlling tide and tidal current evolution. Distribution of shelf sediment types in the BYECS is closely related to tidal current fields during transgression after the LGM.