Sedimentary system response to the global sea level change in the East China Seas since the last glacial maximum

The East China Seas (ECS) is one of the world's largest continental shelf seas. Based on the combination of global sea level change and sequence stratigraphy, we systematically investigated the evolution of sedimentary system in the ECS since the last glacial maximum (LGM). We have defined the transgressive boundary layer and constructed several sedimentary models of the ECS on the sequence stratigraphy and evolution of tidal sand ridges since the LGM, and sediment “source to sink” during the high sea level. The result shows that the ECS represent a typical case for large-scale continental shelf response to the global sea level change. Three sedimentary system tracts had been formed in the ECS since the LGM. First is the lowstand system tract corresponding to the late of last glaciation and LGM (23–15.4cal.kyr B.P.). The progressive wedge occurred along the Okinawa Trough slope and the paleo-coastal zone (PCZ) along the continental shelf edge. Second is the transgressive system tract corresponding to the last deglaciation (15.4–7cal.kyr B.P.). A large-scale transgressive boundary layer and tidal sand ridges were formed in this stage. Third is the highstand system tract corresponding to the high sea level since 7cal.kyr B.P. The eddy mud, coastal current mud, present tidal sand ridge, delta, tidal flat and beach have been accumulating since then. The global sea level change after LGM can be divided into seven phases, of which four rapidly rising phases (RRP, I, II, III, IV) and three slowly rising phases (SRP, I, II, III) are distinguished. The tidal sand ridges were formed in the SRP and transgressive boundary layer in the RRP. The tidal sand ridges can be divided into three types including radicalized, channel and emanative. The modern circulation current system of the ECS had been built in the end of the last deglaciation. The effect of sediment “source to sink” in the ECS is closely correlative to the current system driven by the interaction of the East Asian monsoon and Kuroshio. The major sediment source is from the river discharge of the Huanghe and Changjiang River, and coastal resuspension. The muddy sediment in the eddy and coastal current, which cover the tidal sand ridges and transgressive boundary layer, is a major sediment sink in the modern ECS.