GRAIN SIZE COMPOSITION AND DISTRIBUTION PATTRN OF SEAFLOOR SEDIMENTS IN BOHAI BAY AND ADJACENT AREAS

Based on the measured grain size data of the seafloor sediments taken from the Bohai sea and its adjacent areas, a sediment distribution map is compiled upon Folk's nomenclature system. Some part of the map is modified from the existing maps based on Shepard's classification. Sediments of sandy silt, silty sand, sandy mud, muddy sand, silt and sand are found in the studying area and the depositional characteristics are discussed. According to the integration of sediment distribution, oceanic circulation, bottom topography and sediment provenance (river flux influence), four depositional zones are classified, i.e. the Liaodong mixed depositional zone, the Bohai Bay-Laizhou Bay muddy depositional zone, the Laotieshan Channel-Liaodong-Bozhong sandy depositional zone, and northern Yellow Sea muddy depositional zone. The sediment distribution in the Bohai Sea is obviously dominated by the clastic sediments from rivers and oceanic circulation. The tidal current is the main factor which controls the sediment transportation and differentiation. Muddy sediments settle in weak tide areas while sand ridge and sheet deposits form in strong tide areas.