Fluid mud deposition in macro-tidal flat in the west coasts of Korean during the summer

Abstract

The representative open-coasts tidalflats, Duuri flats, developed extensively along the southwestern coast of Korea shows apparent seasonal change in textural composition of surface sediments: muddy sediments are dominant in summer, while sandy sediments in winter. The reason on such a seasonal change is considered to be erosional process of muddy sediments by strong wind-and/or typhoon-driven waves during the winter. In general, the muds in summer is transported by “suspension mechanism” and then deposited locally in higher-tidal flat. However, it is notably that the summer muddy deposition in Duuri tidal flat occurred in extensive area from lower- to higher-tidal flats. Interpretation on depositional mechanism of such a broaden mud layer during the summer is still not clear. Our data measured by in situ OBS instrument shows that fluid mud are formed in water-sediment interface during the summer. It suggests existence of the high-density mud flow, which is probably responsible for such rapid formation of summer mud layer in Duuri tidal flat with gentle slope. Subsequently, sedimentation mechanisms for seasonally or rapidly summer mud deposition in the open-coast tidal flat such as Duuri flat is closely related with high-density flow of muds.