南黄海辐射沙脊群海域底质粒度特征及其输运趋势

GRAIN SIZE DISTRIBUTION AND TRANSPORTATION TRENDS OF BOTTOM SEDIMENTS IN THE SAND RIDGE FIELD OF THE SOUTH YELLOW SEA,CHINA

为研究南黄海辐射沙脊群海域泥沙输运、地形变化和物质来源,探求黄河、长江迁移的南北界及其输运入海沉积物扩散和影响范围、沙脊群的演变趋势与潮滩的淤涨潜力,对辐射沙脊群海域获取的117个底质沉积物进行了粒度分析和端元组分分析(EMMA),结果表明:研究区底质以粉砂质和砂质沉积为主,区域分异明显,北部的废黄河水下三角洲地区是主要的粉砂质分布区,辐射沙脊群北部以砂质粉砂、中部以粉砂质砂为主,沙脊以细砂质沉积为主,南部粉砂质含量增加。EMMA分析结果显示,黄河和长江泥沙对研究区底质分布影响突出;废黄河三角洲沉积物有向南和东北方向输运的趋势,长江三角洲沉积物向北输运显著,沙脊群中部的细砂质沉积物有向南一直输运到如东—吕四近岸的趋势。与20世纪80年代、90年代调查结果比较,研究区泥质沉积减少,沉积物粗化明显,侵蚀调整突出。

Grain size distribution and end-member-modeling algorithm analysis（EMMA） were conducted for the 117 bottom sediments taken from the radial sand ridge field（RSRF） of the South Yellow Sea.Sediment sources,transportation pattern and topography changes as well as the shifting of boundaries of the Yellow and Changjiang Rivers and their sediments diffusion pattern were studied for revealing the evolutionary trend of the radial sand ridge field and the siltation potential of the tidal flats.The RSRF region is dominated by silt and sand,though there is distinguished lateral variation.There occur silty materials in the subaqueous delta of the abandoned Yellow River,sandy silts in the northern RSRF,silty sands in the central RSRF,fine sands in the radial sand ridges,and more silty materials in the southern RSRF.The results of EMMA reveal that coarse silts from the Abandoned Yellow River Subaqueous Delta（AYRSD） and the Changjiang River have a significant effect on the bottom sediments of the RSRF.The fine materials from the AYRSD have been transported southwards and northeastwards,and the fine materials from the Changjiang River delta transported northwards,whereas the fine sands in the central RSRF have been transported southwards up to the foreshore area.Compared with the samples recovered from the RSRF during the surveys in 1980s and 1990s,fine materials in the whole study area are reduced and the sediments getting coarser as the result,showing an obvious trend of erosion.