导　　师： 张振克

学科专业： 070501

授予学位： 博士

作　　者： ;

机构地区： 南京大学

摘　　要： 圆陀角位于长江北支岸线与江苏海岸线的交汇处,潮滩地貌发育,独特的地理位置与复杂的河海沉积动力,决定粉砂淤泥质潮滩对海岸环境变化具有敏感性响应,潮滩沉积物记录了潮滩环境变化的信息。本文以圆陀角附近潮滩表层和柱状岩芯/(YT、YY和YYZ孔/)沉积物作为研究对象,根据野外观测、沉积物粒度、元素、石英砂扫描电镜、磁化率和137Cs测年等多环境指标分析,结合圆陀角地区近50年来围垦历史,探讨人与自然影响下的圆陀角附近海岸沉积特征及其记录的海岸环境变化。 粒度分析结果表明,圆陀角附近潮滩沉积物以粉砂、砂质粉砂和粘土质粉砂为主,总体上体现了长期淤积背景下粉砂淤泥质潮滩的沉积特征。恒大围垦大堤附近呈现的砂质海岸是潮汐动力分异的结果,即细颗粒物质流向外海,底质砂等粗颗粒物质适应高能环境得以保留。圆陀角附近潮滩岩芯沉积物粒度总体由底部向上呈变细的特点,体现了潮滩自然淤积增高的过程。岩芯粒度记录的一些突变往往与河口海岸环境的变迁、风暴潮以及近期的人类围垦活动有关。 研究区互花米草滩与光滩之间的YT孔和YY孔岩芯137Cs时标计算出的潮滩平均沉积速率为2-3cm//a,自20世纪60年代以来圆陀角附近潮滩平均沉积速率略有下降趋势,与长江北支分水分沙减少、围堤向海推进背景下,圆陀角附近潮汐动力加强有关。根据近年来野外观测,发现风暴潮不仅造成互花米草滩与光滩之间的陡坎侵蚀后退,而且带来大量泥沙在互花米草滩和光滩淤积。在圆陀角北翼恒大集团围堤向海推进之后,长江江堤达标纪念碑附近潮滩淤积明显加强,2007-2009年观测到的淤积速率为4cm//a。互花米草滩和粉砂淤泥质光滩的快速淤积加速了互花米草滩前缘陡坎的消亡,近期圆陀角附近潮滩地貌演化模式是人类活动与潮汐动力特别� The Yuantuojiao Point located at the intersecting point of the coastal lines of the North Branch of the Yangtze River and Jiangsu. The specific geographic location and the complexity of regional morphological dynamics determined the sensitive response of the Yuantuojiao Point silty-muddy tidal flat to environmental changes. The coastlines along the Yuantuojiao Point have shifted eastward about6km in the past50years by the rapid seaward reclamation. Sediments on the tidal flat recorded the information about environmental changes. The surface sediments and three cores /(the YT,YY and YYZ core/) were collected near the Yuantuojiao Point coast. Basing on the field investigation, and the analyses of sediments on grain size, elements, magnetic susceptibility, quartz sand scanning electron microscopy, and137Cs dating methods, combined with50years reclamation history near the Yuantuojiao Point, sedimentary characteristics and its records on coastal environment changes under the backgroud of human-nature interaction along the Yuantuojiao Point coast were discussed in this paper. The grain size analysis results of the surface and cores sediments indicated that silt, sandy silt and clay silt were the main sedimentary type, and this show the typical sedimentary feature of silt-muddy tidal flat under accumulation background at the Yuantuojiao Point. Affected by the levee and storm surges, the coarser sediments were deposited, and the coast at the front of the levee reclaimed by Hengda Group presented the characteristics of sandy shore. The cores sediments became generally finer and finer from the bottom to the top, corresponding to the natural silt-up process of the tidal flat.The mutations recorded by the cores were often associated with environment transition of the estuary-coast, storm surges, and the seaward reclamation near the Yuantuojiao Point. The average sedimentation rates calculated by the137Cs method were about2-3cm//a in the study area. Both the YT Core and YY Core indicated the average sediment rates has d

关 键 词： 潮滩沉积 沉积速率 潮滩地貌 围垦 环境变化 长江北支 圆陀角

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