全新世长江三角洲的发育及其对相邻海岸沉积体系的影响  

Development of the Holocene Changjiang delta and its influence on adjacent coastal sedimentary systems

作　　者：李从先[1] 范代读[1] 

机构地区：[1]同济大学海洋与地球科学学院,上海200092

出　　处：《古地理学报》2009年第1期115-122,共8页Journal of Palaeogeography：Chinese Edition

基　　金：国家海洋局908专项(编号:908-02-02-05);国家自然科学基金项目(编号:40276018;40576030)资助的课题

摘　　要：依据钻孔资料和已发表的文献,对全新世长江三角洲的形成和发育及其对相邻沉积体系的影响作了综合和概括。在末次冰期低海平面时,现今长江三角洲地区可分为下切河谷和两侧的河间地两个古地貌单元。冰后期海平面上升,下切河谷被淹,并转化为河口湾,海水随之扩展到两侧的古河间地。全新世最大海侵时形成以镇江—扬州为顶点的古河口湾。7000～7500年以来,当沉积速率超过海平面上升速度时,长江带来的物质大量沉积,河口湾被充填,并逐渐转变为潮汐平原和三角洲。河口湾被充填之后,长江带来的河流泥沙随之溢出河口湾,进入相邻的河口海岸地区,影响相邻沉积体系的形成和发育。长江泥沙向南进入钱塘江河口湾,在湾顶形成沙坎;向北输运,成为苏北南黄海潮成沙脊的重要物源,影响该潮成体系的形成和发展。舟山群岛海蚀平台上直接覆盖泥质沉积是以退积为主的河口湾向进积的三角洲环境转变的又一证据。长江输沙量在不断减少,而河口滩涂围垦力度在增加,这将导致相邻的河口海岸沉积体系增长速度减缓,出现侵蚀或侵蚀加剧。Based the drilling hole data and published documents, the formation and development of the Changjiang delta and its influence on adjacent coastal systems have been discussed and summarized. The incised valley with palaeo-interfluves at its each sides coexisted in the present Changjiang delta area during the lastglacial lowstand sea level period. The incised valley was gradually inundated when sea-level rose during the postglacial period and a huge estuary was formed. The palaeo-estuary with an apex along the Zhenjiang-Yangzhou section was formed in 7000 -7500 a BP, when transgression reached its maximum. Thereafter, the estuary was gradually converted into tidal plain and delta system when sedimentation rate exceeded the rising rate of sea level. A large quantities of the Changjiang riverine sediments expanded out of the estuary and entered the adjacent Qiantanjiang estuary and Jiangsu coastal zone, when the estuary was filled. A huge sandbody at the bay head of the Qiantangjiang estuary was formed by the Changjiang sediments which were transported by tidal currents. The Changjiang sediments were transported to the north and become a major provenance of the radial tidal sandbodies developed in the northern Jiangsu coastal plain and the southern Yellow Sea. Wavy-erosion platform along the coast of the Zhoushan Archipelago, covered directly by muddy deposits is another record of postglacial evolution of the Changjiang estuary-delta system. Decrease in sediment discharge from the river and increase in trapping more sediments with the delta reclamating landward might lead to sedimentation rate in the adjacent sedimentary environments greatly decelerating, or even the accretional coast turning into erosion.

关 键 词：长江三角洲 钱塘江河口湾 南黄海潮成沙脊体系 海岸沉积 下切河谷 全新世海侵 

分 类 号：P531[天文地球—古生物学与地层学]