DISTRIBUTION CHARACTERISTICS OF GRANULARITIES OF SURFACE SEDIMENTS IN THE SOUTHWESTERN SHELF OF THE EAST CHINA SEA

Based on grain-size analysis data of 65 samples from surface sediments in the southwestern continental shelf of East China Sea, the grain-size parameter calculation and Q-type cluster analysis for the sediments were made,and also their grain-size distributions were discussed in this paper. The main size range of sediments in the study area is from 4 Φ to 10 Φ (coarse silt to coarse clay),fining from coast to sea. The sorting is generally poor, becoming better away from coast. The skewness of sediments changes from -0.52 to 0.77,with negative values near shore. The kurtosis increases in banded distribution from coast to sea and the inshore value is the least.Q-type cluster analysis indicated that the surface sediments in study area can be divided into two groups, including fine-grained sediments in inner shelf and coarse-grained sediments in the outer. These two types show banded distribution,with the demarcation line approximately along 123°E.According to comparison of grain-size cumulative curves from different sampling stations, we can discover that these two types of sediments are deposited in different environments. The inner shelf sediments are modern sediments near shore, and the outer shelf sediments are residual sediments in unconformity with the environment nowadays.