【作者】 陈静；

【导师】 陈中原；

【作者基本信息】 华东师范大学 ， 自然地理学， 2006， 博士

【摘要】 长江，源于青藏高原，横贯我国中部，东流入海，全长约6，400km。长江流域总面积达180余万km~2，约占我国总面积的五分之一。长江流域，山地、丘陵纵横，盆地，平原交错，气候温暖多雨，自然资源丰富，有史以来一直为我国经济发展的重地。长江水系的形成与变迁，对全区地貌的发育起着决定性的作用，关于长江水系的贯通形成与变迁的研究，不仅有重大的理论意义，而且对长远经济规划、水资源的开发利用以及江河、湖沼的整治等均有重大的实际价值。同时，长江贯通入海的研究和中国东西地形倒转以及东海的形成的研究是密不可分，相辅相成的。 流域，特别是大河流域其形成演化发展的过程随着沉积物的搬运堆积也会在经过的盆地中有所反映的。所以，利用河口三角洲沉积物物源变化特征来追踪构造和古气候耦合作用下的河流演化历史已经成为近年来许多学者的关注热点。同样，长江的东西贯通必会将上游青藏高原的物质携带至河口三角洲地区并沉积下来，因此，可以尝试通过研究河口三角洲沉积物中携带的上游物质信息来研究河流源-汇响应机制。 本文对河口区晚新生代钻孔(Pd孔)的不同层位上采集118个样品进行了重矿物鉴定分析，55个样品进行磁学分析。同时，本文总结了长江流域三大岩类(变质岩、侵入岩和火成岩)的分布以及矿物产出特征，对峨眉山玄武岩和中下游赣东玄武岩进行了对比。本课题组还对Pd孔晚新生代以来的335个沉积物样品进行了粒度分析，同时也对63个样品的粘土矿物进行了分析。另外，本文收集了2个晚新生代钻孔的重矿物资料、7个晚新生代钻孔的孢粉以及测年资料；还收集并总结了该区100多个钻孔的地层资料；本文在大量的实验结果和资料总结的基础上，尝试在河流汇区地层中寻找河流贯通入海的证据，从而为古长江演化过程研究展开一个新的角度抛砖引玉。 对长江流域四大盆地(四川盆地、江汉盆地、洞庭湖盆地和鄱阳湖盆地)的地质演化史研究显示出，四大盆地老第三纪至早更新世早期的沉积多为内陆盆地甚至为内陆盐湖沉积，并未受到现代长江的影响。 长江河口区晚新生代以来的沉积物粒度以及沉积相特征表明，上新统-下更新统的地层以粗颗粒为主，沉积环境以冲积、洪积相为主，沉积物搬运距离极短，未经充分改造就快速堆积：下更新统后期过渡沉积物明显增多，分选性有所变好，更多还原

【Abstract】 The Yangtze River is 6, 400km long from Tibetan plateau to the East China Sea and its drainage basin area is more than 1, 800, 000km2, accounting for one-fifth of China national territory. In the drainage basin located are many highlands, hills, intermountain valleys and plains, accompanied by pleasant climate and abundant natural resources that have supported largely economic growth and human societal advancement. Morphological processes of the Yangtze basin have been closely associated with the formation and evolution of Yangtze water system, regarding its significant theoretic importance and long-term economic plan. Moreover, the Yangtze Channelization into sea is closely related to the topographic reversal of the eastern China continent, and to the formation of East China Sea.The fluvial topographic evolution can be recorded as finger-print in its drainage basins sediments, which are transported from sediment sources to sink. The major concern about the long-term river evolution arisen by many geomorphologists is given to the provenance sediment affected by coupling tectonic and paleoclimate interaction, highlighting sediment tracer to the sink basin. This has become an intensive geomorphological study of the Yangtze River, since its sediment that has been brought to the estuary contains unique sedimentological and mineralogical signal from the upper Tibetan plateau.In the present study, there are 118 sediment samples taken from one sediment borehole (Pd) of 354.5m long and of late Cenozoic age. These samples were analysed for heavy mineral. Additional fifty-five (55) sediment samples were taken from the borehole for magnetic test. Meanwhile, the present study has discerned the information of rocks (metamorphic, intrusive and igneous) and minerals distribution in the Yangtze River drainage area from geological maps and previous research results, especially Hypersthene occurrence in the borehole sediment in relation to the Emeishan basalt in the upper Yangtze basin. In the past years, our research teammates also tested 335 samples of borehole Pd for grain-size and 63 samples for clay minerals, and numerous data on heavy minerals, pollens and dating data were collected from many another sediment boreholes. Strata information of the study area was summed up from more than 100 late Quaternary boreholes. These, together, form the present study database. Based on laboratory experimental results and data synthesis, our attempt was made to aim at evidence of the Yangtze River channelization into the East China Sea, which thereby highlights a new insight into the Yangtze River evolution.更多还原