大连湾附近海域表层沉积物粒度特征及水动力环境指示

Grain size distribution characteristics in surface sediments near the Dalian Bay and their hydrodynamic environmental implications

对大连湾、大窑湾外及其附近海域表层沉积物进行了粒度分析,揭示了该区域大致的沉积特征。结合相关的地质水文资料,探讨了其控制因素,同时对沉积环境进行了初步分析。研究区沉积物粒度组分以砂(平均含量34%)和粉砂(平均含量52%)为主,粘土含量比较少(平均含量14%),且主要分布在研究区中部水下台地之上,各组分相对含量呈东西向条带状分布,与地形分布趋势较为一致。北部近岸水下岸坡区,水深较浅,距离物源区较近且水动力条件复杂,沉积物粒度较粗;向南随水深增加水动力减弱,东部为一水下台地,沉积物粒径偏细。分选较好,粉砂和粘土组分在该区域最为富集,沉积物可能来自于通过东部海域自西向东进入研究区的远源物质;研究区南部水深增加,又出现一水下岸坡,其下地形趋于平坦,该区域在黄海环流体系的作用下,接受了较多来自包括山东半岛水下三角洲的粗颗粒物质。

Based on grain size analysis for the offshore surface sediments of the Dalian Bay, the assemblages and distribution characteristics of grain size are acquired, and their sources and sedimentary environments as well as the dominant factors are also discussed preliminarily. The results indicate that the silt has the highest content with 52% in average, followed by sand with 34%. Clay is enriched in the central plateau subregion with the average content of 14%.They are distributed with strap-shape from east to west, which is consistent with the distribution pattern of minerals there.The coastal shallow-water slope in the north of the study area is characterized by the enrichment of coarser deposition,indicating strong hydrodynamic conditions and nearby source. With water depth increasing southward, the silt and clay fractions, which mainly enrich on a subaquatic platform with better sorting, are considered to be transported from far away.To the further south of the study area with the deepest water off another subaquatic slope, coarse fraction is highest,implying strong hydrodynamic conditions induced by tide currents which pass in and out the Bohai Sea and Yellow Sea Warm Current that enters the Bohai Sea.