摘要
长江三角洲江都-镇江(大港)河段冰后期地层层序可分为早期海侵层序和中、晚期海退层序。早期海侵层序主要包括下部冰消期近源辫状河流相、中部河流相、上部河漫滩相,为一套海进式河床充填层序,在垂向上具有该河段独有的三层结构特点。中、晚期海退层序主要包括前三角洲相、三角洲前缘相和三角洲平原相,在垂向上也具有三层结构特点。冰后期以来,古长江的江面宽度不断变化,沉积中心位置也随之发生多次较大调整:冰消期至全新世早期,中心位置曾不断向南偏移;从全新世中期开始,其中心位置开始北移直至最大海侵结束;最大海侵后,随着三角洲不断进积,其中心位置也开始节节南移直至现今位置;从最大海侵到现在,古长江中心位置可能向南移动大约15 km。
The postglacial strata in Jiangdu-Zhenjiang（Dagang town） mouth of Yangtze River Delta may be grouped into early transgressive sequence and mid-late regressive sequence.The early transgressive sequence,which is a transgressive channel-filling one,consists of near-fountain pigtailed river channel facies formed in deglacial stage in the bottom,river channel facies in the middle and floodplain facies in the upper.Therefore,the sequence has a feature of three beds structure that may be exclusive in the mouth in vertical distribution.The mid-late regressive sequence is composed respectively of prodeltaic,deltaic-front and deltaic plain facies in ascending order.Consequently,the sequence is also characterized by three beds structure.Since postglacial stage,the width of ancient Yangtze River was constantly changing,and the depocenter location also had several adjustments.From deglacial stage to the early Holocene,the depocenter had southward migration continuously.From the mid-Holocene,the depocenter started to move north until the end of the maximum transgression.After the maximum transgression,the depocenter also began to retreat southward steadily until the present location with the delta continued progradation.From the maximum transgression to now,the depocenter of ancient Yangtze River may be moved toward south about 15 km.
出处
《资源调查与环境》
2010年第3期176-184,共9页
Resources Survey & Environment
基金
中国地质调查局地质大调查项目(1212010781020)资助
关键词
冰后期
长江三角洲
地层层序
江都市和镇江市
postglacial stage
Yangtze River Delta
strata sequence
Jiangdu city and Zhenjiang city
