南海北部陆架坡折附近表层沉积物的粒度特征和其输运趋势

Grain size characteristics of surface sediments and their transport patterns near the shelf break of the northern South China Sea

对南海北部陆架坡折附近取的50个表层沉积物样品,作粒度测试,计算粒度参数。粒度分析表明研究区的沉积物主要存在4种类型:含砾砂、砾质砂、砂质砾和含砾泥质砂;沉积物组分中砾石和砂占绝对优势,基本上不含黏土。综合因子分析和聚类分析的结果把研究区划分为4类沉积区:Ⅰ类沉积区属于内陆架沉积区,Ⅱ类沉积区属于陆架坡折上部沉积区,Ⅲ类沉积区属于陆架坡折下部沉积区,Ⅳ类沉积区区属于陆架边缘沉积区,每类沉积区都代表着不同的沉积环境。研究区沉积物的粒径趋势分析结果显示,陆架坡折附近的沉积物主要向内陆架和外陆架边缘或上陆坡输运,同时存在着跨陆架输运和沿陆架坡折输运现象,这与研究区实测的底流方向相一致。本研究表明,南海北部陆架坡折附近的沉积环境和沉积物输运模式比较复杂和特殊。本研究对今后陆架和陆坡区其他相关的研究具有十分重要的指导和借鉴意义。

Fifty surface sediment samples were collected near the shelf break of the continental shelf in the northern South China Sea.The grain sizes were analyzed to investigate the sedimentary environmental zoning and grain size transport trend.The contents of gravel,sand,silt,and clay in the study area are 21.7%,76.8%,1.4%,and 0.2%,respectively.The sediments in the study area are mainly divided into four types,which are(gravel)sand,gravel sand,sandy gravel,and(gravel)muddy sand.The study area can be divided into four types of sedimentary areas based on factor analysis and cluster analysis.Area I is located in the northwest of the study area;it belongs to the sedimentary area of the inner shelf.Area II belongs to the upper sedimentary areas of the shelf break,while Area III belongs to the bottom sedimentary areas of the shelf break.Area IV is the shelf-margin sedimentary area.Finally,the net transport of sediments is analyzed according to Gao-Collins’s GSTA model.The results show that the sediments near the shelf break mainly migrate to the inner shelf and upper slope;some can migrate across the shelf break,and some migrate along the shelf break,which agrees with the bottom current observation at the study area.The study shows that the sedimentary environment and sediment transport patterns near the shelf break of the northern South China Sea are very complex and special.This study has important guidance and referential significance for future related research on the areas near the continental shelf and slope areas.