Research on surface sediment types and distributions from the eastern South China Sea, China

The surface sediments in the eastern South China Sea can be divided into 11 types based on the data of sediment color,grain size analysis,chemical and mineral compositions,microfossils,etc.These sediment types are named as clayey silt with rock debris,shell sand,clayey silt,calcareous clay,calcareous ooze,foraminifer ooze,pelagic clay,silty clay with micro-manganese nodules,siliceous clay,siliceous clay with volcanic ash,silty clay with volcanic ash.These sediments can be attributed into terrigenous,biogenic and volcanogenic,according to their material source and genetic environments of sediments.Of which,terrigenous sediments cover 50% area of sea bottom in the study area,calcareous debris 20%,siliceous debris and volcanogenic sediments 15% respectively.Under being controlled and affected by the factors such as materialsource,seabed feature,volcanic eruption and organism activity,hydraulic conditions,as well as the different depositional environments,the brown sediments are dominated (60.68%),the second is the grey sediments(38.20%),the last is the yellow sediments(1.12%) in the study area.In the sea area of between south of Taiwan Province of China and 17°N,the sediments consist mainly of terrigenous constituents;in the west sea area of the Bashi Channel,the coarse sediments are dominated with sandstone rock and gravel;in the east sea area of Dongsha Islands,calcareous debr is are enriched;in the central and western parts,the sediments are rich in the micro-mang anese nodules;siliceous sediments are widely distributed in the southern and central areas because of deep waters;in the southern part and the north edge of Liyue Bank(Liyue Reef Shoal),sediments are calcareous ooze due to be affected by large quantities of detrital corals.