长江口东北海域表层沉积特征及其物源初步研究

Characteristics and Provenance of Surface Sediment in the Northeastern Yangtze River Subaqueous Delta

摘要: 根据长江口东北部海域表层沉积物测试分析结果，对表层沉积物的类型分布、沉积环境和物源成因进行分析讨论。结果表明，表层沉积类型可分为中细砂、细砂、砂质粉砂、粉砂质砂、粘土质粉砂。结合地形地貌，可分为东侧沙波砂质沉积区、西侧边滩拦门沙砂质沉积区、中部沙席混合沉积区、北支河口泥质沉积区。粒级-标准偏差法识别出各区环境敏感粒组，东部沙波、中部沙席普遍存在占主导地位的粗粒的陆架砂质沉积和现代流系带来的细粒组分。北支河口的泥质沉积和中部沙席区沉积较多的受到粉砂粒级为主的现代长江入海泥沙的影响。从粘土矿物特征推断，研究区的表层沉积物绝大部分来源于长江物质，随转向东北的长江径流和潮流、风暴流的输运沉积于该区，研究区的北部，有局部区域沙质物质来源于随苏北沿岸流向南侧运移的黄河物质。

Abstract: According to the grain size and clay minerals characteristics in the Changjiang (Yangtze River) North Branch subaqueous estuary and its adjacent sea area, the type, distribution and environ-mental implications of the surface sediments are discussed. Surface sediments can be divided into medium fine sand, fine sand, sandy silt, silty sand and clayey silt, overall became coarser from sea to land. Combined with topography and geomorphology features, four depositional zones can be identified, including eastern sand ridge and dunes zone, western sandy beach and bar zone, the central sandy sheet zone, and the North Branch estuary muddy deposition zone. Distinguished the environmental sensitive groups from the sediments by particle size standard deviation method, the dominant coarse-grained shelf sand deposits and fine components transported by modern flow systems widespread in eastern sandy zone and central sandy sheet zone, while muddy deposits in the North Branch estuary and mixed sediments deposits in the central part of the area show the influence of silt and clay particles from the Yangtze river. Clay minerals content and distribution indicated that surface sediment was mainly come from Yangtze River and transported by tidal current, Changjiang Diluted Water and coastal current.