西朝鲜湾潮流沙脊的地质特征及其形成演化机制

The genesis and evolution of tidal sand ridges in the East China Seas Shelf provide critical insights into the paleoenvironmental evolution history of this shallow epicontinental shelf. The tidal sand ridges of West Korea Bay are typical wide estuary (bay) sand ridges, which are different with the sand ridges in the East China Sea shelf and Jiangsu offshore area. Currently, theories relevant to wide estuary (bay) sand ridges are still primitive, and details of the evolution model associated with the sea-level changes have remained poorly understood. In this proposal, on the basis of multibeam bathymetric and side scan sonar data, hydrodynamic measurements, high-resolution shallow seismic profiles, surface and core sediments data, we will decipher in detail the internal sedimentary architecture and the spatio-temporal distribution of the West Korea Bay tidal sand ridges.The high-resolution seismic data combined with geotechnical boreholes and shallow cores will be used to reconstruct the late Quaternary depositional history and chronostratigraphic framework, and then to reveal the genesis and evolution model of the West Korea Bay tidal sand ridges related to sea-level changes. This case study would provide deeper insights into the formation and evolution mechanisms of the wide estuary (bay) sand ridges, and can also be helpful to improve our knowledge of the late Quaternary geological history of the East China Seas shelf.

中国东部陆架广泛发育潮流沙脊，其发育和演化过程是我国陆架边缘海环境演化的重要部分。西朝鲜湾潮流沙脊位于北黄海东部，属开敞型海湾沙脊，与东海陆架和江苏岸外等开阔陆架沙脊相比，具有鲜明的特色，但尚未开展实质性的研究。本项目拟选取西朝鲜湾潮流沙脊为研究对象，通过点(表层和岩芯沉积物、定点海流观测)-线(浅地层剖面)-面(多波束测深和侧扫声纳)三位一体的研究，刻画西朝鲜湾潮流沙脊的三维精细结构和海底微地貌特征，揭示其沉积动力机制；构建该海域晚第四纪以来具有年代地层格架的层序地层模式，揭示西朝鲜湾潮流沙脊的时空发育规律；阐明西朝鲜湾潮流沙脊的形成演化对海平面变化及区域"源-汇"效应的响应关系。研究成果将是开敞型海湾沙脊成因模式和演化机制的有益补充，有助于全面了解晚第四纪以来我国东部陆架的环境演化史，并为研究区工程建设、砂矿开采等提供科学依据。

利用国家专项获得基础资料，并通过收集和综合研究区不同时期水深图件，并结合不同时期卫星遥感图像的解译，利用ArcGIS 空间分析技术，对西朝鲜湾海底地形地貌的空间分布、沙脊的迁移规律进行了初步探讨。利用在南黄海中部获得两根柱样岩芯（~5m），进行了沉积学、矿物学、年代学、地球化学分析，探讨了沉积物来源、沉积通量及环境响应，结果表明南黄海中部的泥质沉积可能主要是长江和北朝鲜半岛河流的混合产物，与海洋环流密切相关的海洋锋面可能是主要的控制因素，初步认为在全新世海侵期间，西朝鲜湾海域的再改造过程可能为南黄海中部提供大量细颗粒物质，而粗颗粒留在原地成为潮流沙脊。此外，通过古地磁测试，构建了西朝鲜湾一根地质浅钻的年代地层框架，探讨了黄渤海陆架发育历史。