Terraces Development and Their Implications for Valley Evolution of the Jinsha River Since Late Pleistocene near Longjie,Yunnan |
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| Authors: | Fenliang Liu Hongshan Gao Zongmeng Li Baotian Pan Huai Su |
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| Institution: | 1.Department of Geographic Information System Science, Hu'nan City University, Yiyang Hu'nan 413000, China;2.Key Laboratory of Western China’s Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China;3.School of Geographic Sciences, Xinyang Normal University, Xinyang He'nan 464000, China;4.College of Tourism and Geography Sciences, Yunnan Normal University, Kunming 650500, China |
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| Abstract: | The drainage evolution and valley development of the Jinsha River is an important issue constantly concerned by researchers in geology and geomorphology. Despite hundreds of years of research, there is a big dispute on the formation time and the evolution process of the fluvial valley. Fluvial terraces are very important geomorphic markers for studying the formation and evolution of the fluvial valley. Through field investigation combined with Electron Spin Resonance (ESR) dating, we confirmed that 5 fluvial terraces were formed, and then preserved, along the course of the Jinsha River near the Longjie, which are all strath terraces. Among them, T5 developed on the base rock, with an age of (78±12) ka; all T4~T1 developed on the lacustrine sediments, named Longjie Group by Chinese, with an age of (29±1.4) ka, (26±2.4) ka, (23±1.4) ka, (18±1.7) ka, respectively. Compared with the global and regional climate change history, the terraces are all the result of the river responding to the climate change. T5 formed at MIS 5/4, and T4~T1 formed at the period of regional climate fluctuation. The relationship of terraces and the Longjie Formation, combined with sedimentary characteristics analysis demonstrate that the Longjie Formation is landslide dammed lake sediment. The landslide and blocking events.seriously influenced the valley evolution, inhibiting the river incising, and making the valley evolution defer to the mode of “cut-landside-damming-fill-cut” in the period of Late Pleistocene. Synthesized studies of the terraces and the correlative sediments indicate that the formation of the Jinsha River valley may have begun in the late Early Pleistocene. |
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| Keywords: | Fluvial terrace Valley landform evolution Jinsha River Longjie |
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