Distribution regularity and sedimentary differentiation patterns of China seas surface sediments

China seas have broad continental shelf, continental slope and deep sea basin, with many rivers entering the seas and transporting a huge amount of terrigenous materials into these seas. The sediments record such environmental information as sealand interactions, sea circulation changes, sea level change, material transport and climate change. The grain size characteristics of sediments can reflect such information as sedimentary dynamics, material sources and transport distance, and the changes of sedimentary environment can be studied through the grain size composition, parameters and various diagrams. Previous researchers have carried out lots of studies concerning the grain size distribution characteristics of China seas surface sediments, and obtained many achievements. However, most of these studies were concentrated on a certain sea area or region, lacking a macroscopic and systematic understanding of the sedimentary types in the whole sea area of China. Based on "1:1 000 000 marine regional geological survey project" performed by China Geological Survey, the authors collected 4300 samples of surface sediments from China seas and, through the sediment grain size analysis in combination with data available, studied characteristics of sea surface sediment deposition type, material sources and migration patterns in China seas. In this paper, the shallow sea and bathyal sediments are mainly divided into 5 and 7 sediment types according to the gravel bearing and non-gravel bearing nature, and the deep-sea sediments are mainly divided into 9 sediment types. The results show that sea surface sediment deposition exhibits varied types and complicated sources, which is mainly controlled by the material sources, hydrodynamic condition and the change of landform. Generally the eastern sea areas exhibit "large rivers-broad shelf-residual slow deposition" banded sedimentary differentiation model, whereas in the sea areas of the South China Sea, there is "short source river-multi-type shelf-rapid gravity flow deposits" ring banded sedimentary differentiation model. The results obtained by the authors provide basic data for studying the macroscopic distribution of marine sediments in China seas and are of great significance for understanding the dynamic process of marine sedimentation. At the same time, the distribution characteristics of sediment grain size also have an indicative significance for sea placers distribution.