东海西南陆架表层沉积物粒度分布特征

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

利用东海西南陆架65个表层沉积物样品的粒度分析资料,进行了粒度参数的计算与Q型聚类分析,进而探讨研究区表层沉积物的粒度分布特征。研究区表层沉积物的主要粒级是4～10Φ(粗粉砂-粗黏土),由岸向海粒度变粗;沉积物总体上分选差,但由岸向海分选变好。Q型聚类分析表明,研究区的沉积物分为内陆架细粒沉积物和外陆架粗粒沉积物两类,平行于海岸线分布,123°E左右是两类沉积物的分界线。对比不同站位的沉积物粒度累积曲线,判断两类沉积物属于不同的成因类型,内陆架的细粒沉积物是现代近岸沉积,外陆架的粗粒沉积物与现今的沉积环境不符,属于残留沉积。

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 O to 10 O （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.