Depositional patterns of sand ridges in tide-dominated shallow water environments: Yellow Sea Coast and South Sea of Korea

Abstract

The continental shelf of the Yellow Sea and the Korean South Sea is a tide-dominated shelf. A number of sand ridges occur in this area which form bathymetric highs. Surveyed were one large sand ridge (Jangan Satoe) along the western (Yellow Sea) coast and a group of mid-shelf sand ridges in the South Sea, to delineate their depositional pattern and probable origin in tide-dominated shallow water environments. Analyses of sediment samples, side-scan sonographs, and seismic profiles reveal that these ridges show regionally different characteristics in morphology, bedforms, and sediment. The sand ridge in the Yellow Sea shows a composite form of various bedforms including sand waves and megaripples. This ridge is interpreted to be in an accretional active stage, maintained by strong tidal currents. In contrast, the sand ridges on the mid-shelf of the South Sea show rounded, single forms without bedforms on them. They are interpreted to represent moribund-type sand ridges in the shelf environment, which were formed near the shoreline during the Holocene sea-level transgression. These ridges developed off the paleo-Seomjin River during a period of a stillstand or slow sea-level rise approximately between 10,000 and 7000 yrs B.P.