Geomorphic evolution of the Yangtze Gorges and the time of their formation
Geomorphic evolution of the Yangtze Gorges and the time of their formation
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DOI：
10.1016/s0169-555x(01)00110-6
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发表时间：
2001-11
期刊：
影响因子：
3.9
通讯作者：
Jijun Li;Shi-you Xie;Mingsheng Kuang
中科院分区：
文献类型：
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作者：
Jijun Li;Shi-you Xie;Mingsheng Kuang
长江三峡将其上游的岩石峡谷与下游的冲积区连接起来。三峡库区、四川盆地上游和江汉盆地下游存在一系列阶梯式地貌。这些地貌的特点是两个平坦面，一个侵蚀面和多达七个阶地。较高的夷平面（约1800 ~ 2000 m a.s.l.）和较低的夷平面（1200 ~ 1500 m）可能形成于第三纪（3.4 ~ 3.6 Ma B.P.之前）。早期的水系与现在的长江水系之间似乎不存在相关性。研究区海拔800 ~ 1200 m的侵蚀面形成于早更新世晚上新世。在最后一次夷平事件之后的这一时期，长江祖先可能已经开始调整其排水网络。这7个阶地发育于早更新世至晚更新世（1.16 ~ 0.01 Ma b.p.）。从四川盆地到三峡至江汉盆地，其年代地层证据和诊断沉积物在时间和空间上基本具有可比性。因此，本研究认为三峡的切割不晚于最早阶地的起始。长江三峡的河流地貌还具有谷中谷剖面的特征，即一个较老的u型谷被一个较年轻的v型谷切割。该地区主要是构造隆起伴随着河道的快速下切。
The Three Gorges of the Yangtze link its upper rocky valley to downstream alluvial sections. A series of stepped landforms exist in the Three Gorges area, the Sichuan Basin upstream and the Jianghan Basin downstream. These landforms are characterized by two planation surfaces, one erosional surface, and up to seven terraces. The higher planation surface (named the Exi Surface, ~1800–2000 m a.s.l.) and the lower planation surface (1200–1500 m) were probably formed in the Tertiary (prior to 3.4–3.6 Ma B.P.). No correlation seems to exist between the drainage networks of earlier period with the present Yangtze system. It is suggested that the erosional surface found in the study area at 800–1200 m in elevation above sea level was formed in Late Pliocene of Early Pleistocene. During this period following the last planation event, the ancestral Yangtze might have begun to adjust its drainage network. The seven terraces, well developed along the eastern Sichuan Basin and the Three Gorges, date from Early to Late Pleistocene (1.16–0.01 Ma B.P). The chronostratigraphic evidence and diagnostic sediments are generally comparable in time and space from the Sichuan Basin, through the Three Gorges, to the Jianghan Basin. Therefore, the present study proposes that the Three Gorges were cut not later than the initiation of the earliest terrace. The fluvial landforms in the Yangtze Gorges are characterized also by valley-in-valley cross-sections, i.e. an older U-shaped valley cut by a younger V-shaped valley. A tectonic rise accompanied by a rapid downcutting of the river channels predominated in the region.