镇江—扬州长江河谷第四系沉积演变特征

EVOLUTIONARY CHARACTERISTICS OF THE QUATERNARY SEDIMENTS IN THE YANGTZE VALLEY BETWEEN YANGZHOU AND ZHENJIANG

镇江、扬州间之长江河谷是拟建长江公路大桥桥址比选的优异地段。勘察资料证实 :河谷第四系由上更新统中段、全新统中上段组成、海侵、海退及新构造运动的升降制约了第四系沉积与演变 ,致使第四系呈现侵蚀不整合、半旋回序列。河道经历了山前河流、河口沙坝、三角洲平原的发育阶段 ,河道在自北而南迁移总趋势下 ,曾有多次往复摆动 ,现今仍在向南侧蚀。沿江岸带城镇座落、人口稠密、经济繁荣、素有“金三角”之称 ,不言而喻 ,加强其沉积演变势态的研究具有特殊的社会与经济意义。

The Yangtze Valley between Yangzhou and Zhenjiang is an excellent sector for the building of the designed Yangtze River highway bridge. Exploration data show that the Quaternary of the river valley is composed of the middle member of the Upper Pleistocene and the upper and middle members of the Holocene and the marine transgression, regression, and the neotectonism controlled the sedimentation of evolution of the Quaternary, causing the Quaternary to be a semicyclic sequence with a unconformity by erosion. River course experienced a development stage of piedmont river, channel mouth bar, and deltaic plain and has changed for many times during its shift from north to south, still eroding the southern side at present. Cities and counties along the banks of the river have a dense population and a prosperous economy and have long been known as “golden delta”. It is self evident that an intensive study of the sedimentary evolution may be of special social and economic significance.