南海西北部海域表层沉积物粒度分布特征及其影响因素

对南海西北部海域416个表层沉积物样品进行粒度和多元统计分析,结果表明研究区沉积物类型复杂,从粗粒级的砾石到细粒级的黏土皆有发育,共分为14种类型。其核心粒级为4 φ~9 φ,占71%,平均粒径范围为0.99 φ~7.44 φ;分选系数为0.54~3.72;偏态范围为-0.32~0.78;峰态范围为0.62~3.92。R型聚类分析结果表明表层沉积物基本上分为粗、细2大类:粗颗粒沉积物由-2 φ~5 φ粒级组成,细颗粒沉积物由6 φ~11 φ组成。R型因子分析结果表明前5种因子累计特征值比例达到89.38%。因子1、因子2和因子3是主导因子:因子1主要由9 φ~11φ的正载荷和3 φ~4 φ的负载荷组成;因子2主要由6 φ~8 φ的正载荷组成;因子3主要由-2 φ~0 φ的正载荷组成。研究区粗粒沉积物一般在水动力较强的陆架区沉积,其分选较好,物质来源多样;细粒沉积物主要位于水动力弱的海湾、离岸较远的陆架以及陆坡和海盆区,其分选差,物质来源单一。

GRAIN-SIZE DISTRIBUTION OF SURFACE SEDIMENTS IN THE NORTHWESTERN SOUTH CHINA SEA AND INFLUENCE FACTORS

Grain size analysis and multivariate statistics have been carried out for the 416 surface sediments collected from the northwestern South China Sea.There are 14 types of sediments from gravel to clay,dominated by the sediment of 4Φ~9Φupto 71%.The sediments vary between 0.99Φ~7.44Φ in mean grain size,0.54~3.72 in the coefficient of sorting,-0.32~0.78 in skewness and 0.62~3.92 in kurtosis following the formulas by Folk et al..R-mode cluster analysis shows that there are two clusters.The first cluster is composed of the sediments of-2Φ~5Φ,and the second cluster consists of the sediments of 6Φ~11Φ.The total eigenvalue of the first 5 factors is up to 89.38%,with the factor 1,2 and 3as the main.The factor 1 is composed of the positive load of 9Φ~11Φ and negative load of 3Φ~4Φ.The factor 2 consists of positive load of 6Φ~8Φ and the factor 3 of negative load of-2Φ~0Φ.Coarse sediments,which are well sorted,are mainly distributed on the continent shelf with strong hydrodynamics and multiple sources.To the contrary,fine sediments,which are usually poorly sorted,often lie in low energy environments,such as the gulf,low energy continental shelf,continental slope and deep basin with a simple source.