南海东部海域沉积物粒度分布特征

Characteristics of Grain Size Distributions of Surface Sediments in the Eastern South China Sea

对南海东部海域 179个站表层沉积物作了粒度分析、粒度参数计算和多元统计分析 ,结合有关资料探讨了南海东部沉积物粒度分布特征、沉积物运移方式和沉积环境。南海东部表层沉积物主要粒级是 4 .0～ 10 .0(粗粉砂—粗粘土 ) ,核心粒级是 6 .0～ 8.0(细粉砂 ) ,火山灰沉积物平均粒径 4 .4 6～ 6 .4 0 ,平均 5 .6 9。粒度R型聚类分析得出三群 :第一群由 1.5～ 3.0、9.5～ 14 .0粒级组成 ,也就是粗、细两端粒级。第二群由 3.5～ 5 .0粒级组成。第三群由5 .5～ 9.0粒级组成。各粒级归类良好 ,图形清晰。R型因子分析结果表明前 4种因子累计特征值比例达 94 .5 0 % ,因子 1和因子 2是主导因子。因子 1主要由负载荷粗粉砂级和正载荷粘土级物质构成。因子 2主要由负载荷极细砂级和正载荷细粉砂级物质组成。因子 3和因子 4分别由悬浮质 (0 .0 6～ 0 .12 μm)和中砂 (2 5 0～ 35 4 μm)组成。沉积物因子作用分区与物质来源、海流、地形和沉积作用密切相关。南海东部沉积物中粉砂和粘土含量总体上由北向南呈线性逐渐增加 ,平均粒径和峰态也有同样的变化趋势 ,分选系数和偏态则明显地反映出在约 17°N呈急剧下跌和上升 ,这些现象表明 17°N是南部、北部沉积物类型分界线位置。沉积物粒度。

Grain size analysis, parameter calculation and multivariate statistics have been carried out based on 179 surface sediments collected from the Eastern South China Sea, and using related data, characteristics of frequent distributi on, sediment movement style and sedimentary environments have been researched. T he major class of surface sediments of the Eastern South China Sea are composed of 4.0～10.0(coarse silt-coarse clay), the key class consist of 6.0～8.0(fi ne silt), mean( M z ) of ashy sediments is 4.46～6.40 and the average is 5.69. There are three clusters based on R-mode cluster analysis of the grain size data: First cluster is composed of 1.5～3.0 and 9.5～14.0, situating co arser part and finer part on the frequent distribution curves. Second cluster co nsists of 3.5～5.0 and third of 5.5～9.0. The grain size classes are well cl ustered and their feature is clear. The result of R-mode factor analysis shown that the eigenvalue of prior 4 factors is 94.50%, factor 1 and 2 is main factors . Factor 1 is composed of minus loads of coarse silty class and plus loads of cl ayey materials. Factor 2 consists of minus loads of very grained sand class and plus loads of fine silty materials. Factor 3 and 4 are composed of suspended sed iments(0.06～0.12 μm)and medium sand(250～354 μm) materials, respectively . The factor effect districts are related to the sediment provenance, current, s ea floor feature and sedimentation. Contents of silt and clay shows general tren ds of increasing from north to south, and similar to the trends of mean and kurt osis. Coefficients of sorting and skewness indicate the boundary of sediment typ es between northern and southern South China Sea locate about 17°N because thei r values change heavily up and down near 17°N. According to analysis of grain s ize, composition and biogenic fossil assemblage of the core sediments, the follo wing layers of 187.5～190 cm, 287.5～280 cm and 377.5～380 cm in 69 sediment column collected from the northern continent slope, 157～187 cm and 187～194 c m in 149 column from the abyssal plain, 280～350 cm in 323 column from the sout hern continent slope are characterized by the turbidity deposits.