Characterization of grain size parameters and the provenance analysis of the surface sediment in the outer shelf of the northern South China Sea

In order to discuss the provenance of surface sediment in the outer continental shelf of the northern South China Sea,18 surface sediment samples in the continental shelf were sampled and tested.Through the computation of average grain size,sorting coefficient and other grain size parameters,distribution of grain size parameters of surface sediment was obtained and analyzed.All samples can be classified into seven types in terms of grain size,which were gravel,sandy gravel,gravelly muddy sand,sand containing gravel,muddy sand containing gravel and mud containing gravel.From outer continental shelf to inner continental shelf,the changing trends of different grain size parameters were conspicuous,average grain size became smaller,sorting coefficient became larger,skewness became more positive,and kurtosis became larger.At sampling position that was closer to the continent of South China,diversity of provenance of surface sediment was strengthened.Hydrodynamic condition transporting the sediment comes from the WNW-N direction current,driving the sediment from SE to NW to the inner continental shelf.To the inner continental shelf,which is closed to China mainland,ratio of sediment transported from South China by the Pearl River and the Han River became bigger in the composition of surface sediment.