长江口及邻近海域现代沉积速率及其对长江入海泥沙去向的指示意义

对长江口及附近海域的16根重力柱样进行了210Pb沉积速率测试, 结合以往成果, 揭示了该区现代沉积速率分布格局, 对其控制因素以及其对认识长江入海泥沙去向的指示意义进行了探讨.沉积速率最高值分布在南支口外、杭州湾口群岛北部的前三角洲地区, 最高可达6.3m/a, 总体上在3cm/a以上; 次高值分布在杭州湾北部, 约1.7~3.0cm/a, 南部略低, 约0.4~1.0cm/a; 长江口水下负地形北部海域存在小片沉积速率较高的区域, 最高值达2.58cm/a; 低值主要分布在苏北辐射沙洲、过渡沉积区以及浅海陆架的大片区域, 基本保持在1cm/a以下.研究表明, 长江泥沙出口门后主要在水下三角洲地区进行了堆积, 其次有相当部分在涨潮流顶托下进入杭州湾, 进入杭州湾南部的泥沙又在落潮流作用下经杭州湾南侧向舟山海域方向输运; 长江入海物质向外海的扩散基本被控制在123°E以西, 苏北辐射沙洲、过渡沉积区以及浅海陆架的大片区域缺乏现代长江物质供应; 长江悬浮泥沙对研究区东北部陆架区影响较小, 废黄河口被侵蚀物质和黄海悬浮物质为其较高沉积速率的主要贡献者. 

Sedimentation Rates and Its Indication to Distribution of Yangtze Sediment Supply around the Yangtze (Changjiang) River Estuary and Its Adjacent Area, China

Based on 210Pb data of 16 gravity core samples and from the previous study, the spatial pattern of sedimentation rates and its indication to distribution of Yangtze sediment supply in the Yangtze River estuary and its adjacent area were examined. The high accumulation rates were observed at the subaqueous delta off the south branch with the maximum value of 6.3cm/a, generally above 3cm/a. The second highest values distribute on the Hangzhou bay, about 1.7-3.0cm/a in north and much lower in south (0.4-1.0cm/a). Relative higher sedimentation rates, about 2.58cm/a, appear in the northwest of study area. The radial sand ridges along the north Jiangsu coastal line, delta-shelf transitional zone and continental shelf were characterized by low sedimentation rates (< 1cm/a), due to the strong hydrodynamic setting and lack of modern Changjiang material supply. As revealed by this study, a large amount of Yangtze sediment load is deposited around the subaqueous delta and the north Hangzhou Bay. The dispersion of modern Yangtze sediment to East China Sea is constrained to the west of 123°E. The relatively high sedimentation rate in north continental area is mainly contributed by sediment eroded from the abandoned Yellow delta and suspended materials transported by Yellow Sea longshore currents.