南黄海西部日照至连云港海域表层沉积物粒度特征及其指示意义  

GRAIN-SIZE CHARACTERISTICS OF BOTTOM SEDIMENTS AND ITS IMPLICATIONS OFFSHORE BETWEEN RIZHAO AND LIANYUNGANG IN THE WESTERN SOUTH YELLOW SEA

作　　者：秦亚超[1,2] 

机构地区：[1]国土资源部海洋油气资源与环境地质重点实验室青岛海洋地质研究所,青岛266071 [2]海洋国家实验室海洋矿产资源评价与探测技术功能实验室,青岛266071

出　　处：《第四纪研究》2017年第6期1412-1428,共17页Quaternary Sciences

基　　金：国土资源部海洋区域地质调查项目（批准号：GZH201400206）资助

摘　　要：基于南黄海西部日照至连云港海域200件表层沉积物样品的粒度分析结果，划分了沉积分区，探讨各分区的沉积物来源、长期运移趋势、沉积分区的成因和可能的搬运机制。结果表明，日照至连云港海域可划分为4个沉积分区，分别为中部海侵沉积区、西北部的日照近海现代沉积区以及南部的苏北废黄河水下三角洲和连云港沿海侵蚀再沉积区，特点为：1）海侵沉积区表层沉积物几乎全部为粉砂质砂，砂含量平均可达64%（剔除砾组分）。钙质结核砾石分布广泛，尤其富集在20m以深海域。该层砂质碎屑是全新世早期海侵作用的产物，应归为海侵沉积，其物源来自于原地出露的晚更新世古湖沼相或古河流相沉积物，因而具有继承性特征。2）日照近海沉积区为全新世现代沉积，沿日照海岸呈狭长带状分布，主要是砂质粉砂和粉砂。3）苏北废黄河水下三角洲的北界位于连云港埒子口外，水下三角洲前缘陡坡在120°E附近大约位于水深23m处。水下三角洲废弃后夷平作用较为显著。地势较高的水下台地剥蚀强烈，表现为硬质底的出露；而在水深相对较大或水动力较弱的局部区域，侵蚀物质再次沉积。剥蚀亚区沉积物为具有单峰态粒度曲线的粉砂质砂，而侵蚀再沉积亚区则为具有双峰态粒度曲线的砂质泥、砂质粉砂和粉砂质砂，两者差异明显，在沉积物组成和粒度参数分布图上呈现条块分割的现象，这实际上反映了夷平过程中剥蚀亚区和再沉积亚区的伴生关系。4）连云港沿海沉积区以具有双峰态粒度曲线的砂质泥和砂质粉砂为主，是淤泥质海岸侵蚀物质离岸搬运后与砂质沉积物混合改造的结果，实质上应为变余沉积。Grain-size analysis was carried out to classify depositional areas according to 200 bottom sediment samples obtained offshore between Rizhao and Lianyungang in the western South Yellow Sea. It was further discussed referring to sediment sources, long-term trends of sediment transport, origin of depositional areas, and possible transport mechanisms. These 200 sampling localities were evenly arranged based on 4km×5km grids to the west of longitude 120°E. Results show that four depositional areas are recognized, respectively, as the transgressive depositional area, the Rizhao nearshore depositional area, the abandoned subaqueous Yellow River delta, and the Lianyungang coastal depositional area. （1）In the transgressive depositional area, the bottom sediments are almost composed of silty sand, with an average sand content of 64% （removal of pedogenic calcretes）. Calcrete-formed gravels are exposed extensively on the sea floor, especially in water regimes deeper than 20m. These sandy detritus accumulated by transgression in the early Holocene, and hence belong to transgressive deposits. Their provenance is contributed to exposure and reworking of the autochthonous Late Pleistocene sediments with yellow paleo-fluvial or paleo-lakeshore facies. （2）The Holocene sediments with sandy silt or silt are present along the Rizhao coastal zone like a narrow band. （3）The north boundary of the abandoned subaqueous Yellow River delta is located off Liezikou, and the steep slope of the subaqueous delta front is located at water depth of 23m near 120°E. This subaqueous delta has been suffering from deplanation since it was abandoned in 1855. Subaqueous platforms with higher altitudes are denuded intensively, showing hard layer exposure; whereas in local regimes with relatively deeper water or weaker hydrodynamics, the eroded sediments deposited again. The bottom sediments in denudational subareas consist of silty sand with unimodal grain-size distribution, whereas in re-depositional subareas they are sandy mud, sand

关 键 词：粒度 表层沉积物 海侵沉积 钙质结核 废黄河水下三角洲 南黄海 

分 类 号：P512.32[天文地球—地质学] P736