越南红河水下三角洲北区表层沉积物类型及分布特征初探

对2007年采自越南红河水下三角洲北区24个表层沉积物样品进行了粒度分析和粒度参数计算,初步探讨了该区沉积物的主要类型及分布特征。结果表明,越南红河水下三角洲北区的表层沉积物主要由粉砂组成(体积平均含量为54.35%),平均粒径为6φ。按Link沉积物命名法,该区沉积物主要类型有砂、砂质粉砂和黏土质粉砂。水平分布上,由西部的砂向东逐渐变为黏土质粉砂,呈现出由近岸三角洲前缘相的粗粒级沉积物逐渐向前三角洲-浅海相的细粒级沉积物变化的趋势。与前人研究成果对比发现,红河水下三角洲北区沉积物黏土的比例较1996年的比例明显增大,可能与海岸线近10a来总体上呈向陆迁移、水下三角洲沉积向岸蚀退以及纵向上水动力逐渐变弱有关。

Study on surface sediment characteristics and distribution in the northern Red River subaqueous delta, Vietnam

Based on the grain size analysis and relevant parameter values of 24 surface sediments from the northern Red River subaqueous delta in Vietnam in 2007,we preliminary discussed main sediment types and the distribution characteristics.The results shows that the surface sediments in the northern Red River subaqueous delta in Vietnam are mainly composed of silt,which is 54.35% in volume content,and 6φin size,and three main sediments types are classed into sand,sandy silt and clayed silt according to the Link nomenclature .In general,the sediment grain size becomes fine westward from sand to clayed silt,corresponding to the change of sediment unit from delta front with coarse sediments to prodelta-shelf with fine sediments.In addition,comparing with previous study results,we find that the proportion of clay in sediments is much more than that in 1996.The obvious increase of clay content may be related to coastline landward migration,subaqueous delta degration landward in part and hydrodynamic action decreasing within 10 years.