Depositional processes of late Quaternary sediments in the Yellow Sea: a review

This review focuses on the depositional processes of late Quaternary sediments in the eastern Yellow Sea, an epicontinental sea with a flat and broad seafloor (less than 100 m in water depth) and extensive tidal flats along the southeastern coast. The Yellow Sea was subaerially exposed during the last glacial period when sea level was about 120 m below the present level. During erosional retreat of shorefaces and river mouths, sedimentation was largely controlled by high-amplitude rise in sea level, forming transgressive sheets (echo type 1-3a) and sediment ridges (echo types 2-1 and 2-2) with extensive development of ravinement surfaces. The distribution of surface sediments reflects an interplay of sediment input from the surrounding landmass and the hydrodynamic regime in response to sea-level rise. Muddy sediments in the central part represent the Huanghe-River source and form a highstand sheet (echo type 1-3b). Large birdfoot-like sand bodies off the Jiangsu coast also represent highstand deposits when sea level reached the present position at about 6 ka. In the southeastern part of the Yellow Sea, sediments are dominated by sand ridges (echo types 2-1, 2-2 and 2-3), largely shaped by tidal currents. The southwestern corner of the Korean Peninsula is dominated by a thick deposit of mud, the Heuksan mud belt. The muds largely originate front the Geum River, whose distribution is controlled by strong southward coastal currents. In the coastal regions of the southeastern Yellow Sea, sedimentation is controlled by a combined effect of waves and tides with distinctive seasonalities in sedimentary facies owing to the monsoonal climate: tide-dominated mud deposition in summer and wave-dominated sand deposition/erosion in winter. Winter storms play a role in sedimentation on intertidal flats. Quantitative monitoring of sediment transport suggests that the textural variation results from the overwhelming role of winter waves superimposed on tidal currents in putting sands and resuspending muds. Due to low sedimentation rate, the tidal flats formed retrogradational, coarsening-upward pattern during the Holocene sea-level rise.