| 黄河源地区的河谷地貌特征及其对黄河上游形成和演化的启示 |
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| 引用本文： | 赵卿宇,肖国桥,李辉.黄河源地区的河谷地貌特征及其对黄河上游形成和演化的启示[J].第四纪研究,2019,39(2):339-349. |
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| 作者姓名： | 赵卿宇 肖国桥 李辉 |
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| 作者单位： | 中国地质大学(武汉)地球科学学院,湖北 武汉,430074;中国地质大学(武汉)地球科学学院,湖北 武汉 430074;中国地质大学(武汉)生物地质与环境地质国家重点实验室,湖北 武汉 430074 |
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| 摘 要： | 黄河的形成与演化对于认识我国宏观地貌格局的形成、青藏高原及黄土高原的区域构造活动历史、华北平原及黄渤海陆架的形成和演化等问题具有重要意义。目前对黄河演化历史的研究主要集中在龙羊峡以下的河段,对于黄河源段的关注较少。文章基于黄河源地区河谷地貌的实地考察,并利用SRTM1-DEM数据,分析了黄河源段干流及支流河谷橫剖面的地貌特征,并与该区典型的冰川谷和兰州附近黄河的河谷横剖面进行了对比。结果表明:黄河源地区的河谷规模巨大,并呈现出谷底开阔、河床窄小、阶地不明显、谷坡陡立、河谷横剖面左右对称的U型谷特征。这些特征与该区冰蚀谷的特征相似,但与兰州段黄河成型河谷的特征相差甚远,且其河谷规模更大。我们推断,黄河源地区的河谷可能主要为冰期时的冰蚀作用所塑造,而非单纯的流水侵蚀形成。由于冰蚀作用的存在,该区早期的河流阶地可能被随后冰期的冰蚀作用所破坏,当前基于黄河源地区现存河流阶地年代的研究很可能低估了该区水系的发育历史。此外,反复的冰川进退也可能导致黄河源水系自上而下贯通,而非溯源侵蚀形成。
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| 关 键 词： | 黄河源 河谷地貌 河流阶地 冰蚀作用 |
Valley features of the Yellow River source area and its implications for the formation and evolution of the upstream |
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| Zhao Qingyu,Xiao Guoqiao,Li Hui.Valley features of the Yellow River source area and its implications for the formation and evolution of the upstream[J].Quaternary Sciences,2019,39(2):339-349. |
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| Authors: | Zhao Qingyu Xiao Guoqiao Li Hui |
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| Institution: | (School of Earth Sciences,China University of Geosciences(Wuhan),Wuhan 430074,Hubei;State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences(Wuhan),Wuhan 430074,Hubei) |
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| Abstract: | The Yellow River is the second longest river in China.Its formation and evolution history are of great significance for understanding the macro-geomorphological pattern of China,the tectonic activity history of the Tibetan Plateau and Chinese Loess Plateau,and the sedimentary environment evolution of the North China Plain,Bohai Sea,and Yellow Sea continental shelf.Most studies concentrate on the evolution history of middle and lower reaches of the Yellow River,its uppermost reaches,however,lack investigation.Based on field investigation and SRTM1-DEM data,we analyzed the geomorphic features of the cross sections of the Yellow River valley in the source area,and compared them with typical glacial valleys in this area and the Yellow River valley near Lanzhou City,respectively.We found the valleys in the Yellow River source area exhibit a U-shaped character,and the bottom of the valley is rather broad,with few terraces,but the stream bed is very narrow.These features are significantly different from the Yellow River valley near Lanzhou,but similar to the glacial valley in the Yellow River source area.Furthermore,the scale of the valley in the source area is even greater than that at Lanzhou,albeit the age of terrace in the source area(latest Pleistocene)is much younger than that at Lanzhou(Early Pleistocene).This apparent contradiction can be reconciled by considering these valleys are glacial valleys.This hypothesis is supported by previous glacial studies,which demonstrate that there were massive glacial activities during the glacial periods since Middle Pleistocene.The periodical glacial activities have several important implications for understanding the formation and evolution of the upstream of the Yellow River.First,the glacial erosion may have played an important role in shaping the valley in the source area of the Yellow River.During the glacial periods,strong glacial erosion would carve a U-shaped valley;while in interglacial periods,river would occupy the bottom of the valley,and develop some river terraces.Second,glacial activities would erode the terraces formed in previous interglacial,and this will lead to underestimate the evolution history of the Yellow River.Therefore,it needs to reevaluate the latest Pleistocene age of the headwater system of the Yellow River reported by previous studies based on terraces dating.This suggests that it should be cautious when use the river terrace age as the indicator of the fluvial evolution history,especially in the areas with strong glacial activities.Third,the repeated extension and retreat of glacial in the Yellow River source area may have led to integration of the uppermost reaches by glacial erosion or spillover of melting water,other than headward erosion. |
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| Keywords: | the source area of the Yellow River fluvial valley geomorphy terrace ice erosion |
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