末次冰消期以来黄海暖流演化：沉积物硅酸盐碎屑Sr-Nd同位素示踪

The formation of Yellow Sea Warm Current (YSWC) is an important geological event in the Yellow Sea since the last deglaciation, which has a strong impact on the dynamic structure, mass transport, ecological environment and local climate of Yellow Sea. It is a new research hotspot for tracing paleocirculation using Sr-Nd isotopic composition in silicate components of sediments. Nine sediment cores were collected from the pathway of YSWC in the Yellow Sea. The objectives of this research are: to determine the environmental sensitive grain-size groups based on the sediment grain-size parameter analysis and end-number model; to identify and quantify the contributions of different sources (Changjiang, Huanghe, Yalujiang, Korean peninsula rivers and tephra deposits in the Okinawa Trough) based on the Sr-Nd isotopical components in silicate debris components; to reveal the variations of sourece and fluxe of sediments in the pathway of the YSWC through analysis the data including mineral, elements and AMS14C; to study the role of Sr-Nd isotopic composition in sensitive grain-size silicate components as tracing the paleocirculation, based on the response between current drive and material transporting; to determine the time of appear and formtion of YSWC by discuss the the distribution pattern of tephra deposits in the Okinawa Trough; and to reconstruct the evolution process of the YSWC since the last deglaciation. The results of this research will provide these basical data for investigation the effects of Kuroshio Current on circulation structure, mass and heat transport pattern, marine ecological environment and local climate of China offshore.

黄海暖流形成是末次冰消期以来黄海最重大的地质事件，影响海域动力格局、物质输运、生态环境和气候变化。沉积物硅酸盐组分同位素示踪是当前环流演化研究的热点。课题以暖流流经区柱状样品为对象，测定沉积物硅酸盐碎屑粒度组成，在粒度参数分析和端元模拟的基础上确定敏感粒级组分；根据硅酸盐组分Sr-Nd同位素组成，通过混合模型定量识别不同粒级组分物源（长江、黄河、鸭绿江、朝鲜半岛河流及冲绳海槽火山物质）的贡献；结合样品矿物组合、元素组成及AMS14C年龄，揭示硅酸盐敏感粒级组分物源及通量变化；从环流搬运驱动与物质输运响应角度研究敏感粒级硅酸盐组分Sr-Nd同位素对黄海暖流路径及强度的示踪作用；分析冲绳海槽火山物质含量及通量时空分布规律，确定暖流启动及贯通时间。综合分析上述成果，重建末次冰消期以来黄海暖流演化历史，为黑潮入侵对我国近海物质输运模式、环流与水团结构、生态系统和局域气候变化研究提供基础地质资料。

黄海暖流的形成是末次冰消期以来黄海最重大的地质事件，影响海域动力格局、物质输运、生态环境和气候变化。课题以黄海暖流流经区及其水源发源区为研究靶区，获得了多站岩芯沉积物AMS14C年龄、Sr-Nd同位素组成、元素组成、碎屑和粘土矿物组成、粒度、有机碳氮和黄海暖流余流区Pb同位素组成及元素组成等数据。通过Sr-Nd同位素二端元混合模型和粘土矿物组合定量识别了全新世以来黄海暖流流经区沉积物不同物源（长江、黄河、朝鲜半岛河流、冲绳海槽沉积物等）贡献的时空变化。确定黄海暖流形成于约中全新世（约6.5ka），阐明了自中全新世以来黄海暖流强度在时间和空间上的变化；揭示了黑潮和对马暖流流强对黄海暖流形成的影响，认为黑潮和对马暖流是黄海暖流的主要水源。黄海暖流的形成对黄海沉积动力格局和物质输运影响深远，其形成推动了南黄海气旋和反气旋型涡旋环流的形成，有利于黄河细粒物质在南黄海中部沉积并形成中部泥质区。黄海暖流既可将部分冲绳海槽物质输运至南黄海，同时也阻挡了朝鲜半岛物质向西输运。黄海暖流余流对渤海沉积动力学、物质输运和生态环境也有影响，结果显示黄海暖流余流在一定程度上制约了渤海沉积物中Pb和Cd等污染物进入黄海。