地理学报 ›› 2018, Vol. 73 ›› Issue (7): 1338-1352.doi: 10.11821/dlxb201807012

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长江源地区通天河段水系格局演化与构造活动的关系

于洋(),王先彦(),李一泉,戴岩,鹿化煜   

  1. 南京大学地理与海洋科学学院,南京 210023
  • 收稿日期:2017-08-07 出版日期:2018-07-25 发布日期:2018-07-13
  • 基金资助:
    国家自然科学基金项目(41522101);国家重点研发计划(2016YFA0600500);中央高校基础研究基金项目(020914380043);中荷交流项目

The evolution of drainage pattern and its relation to tectonic movement in the upstream Yangtze catchment

YU Yang(),WANG Xianyan(),LI Yiquan,DAI Yan,LU Huayu   

  1. School of Geography and Ocean Science, Nanjing University, Nanjing 210023, China
  • Received:2017-08-07 Online:2018-07-25 Published:2018-07-13
  • Supported by:
    National Natural Science Foundation of China, No.41522101;National Key Research and Development Program, No.2016YFA0600500;The Fundamental Research Funds for the Central Universities, No.020914380043; Dutch-Chinese Exchange Program

摘要:

青海玉树地区长江源区通天河段构造运动活跃,地震频发,如2010年曾发生7.1级地震;该地区分布有黄河、雅砻江、澜沧江等水系上游河网,水系呈直角状、倒勾状分布,是研究水系演化与新构造活动关系的理想区域。通过地形分析、河流水系分析和地貌指数计算,探讨了该地区水系格局演化对走滑断层相关构造活动样式的响应过程。该地区主要发育北西—南东和南西—北东两组流向的水系,其中北西—南东向河谷多为低河流比降、宽阔的不适称谷地,而南西—北东向河谷多为高河流比降、陡峭的峡谷。河流陡峭度指数(ks)在通天河东南段为高值,在通天河流域西南段多采曲—宁恰曲流域、登艾龙曲流域、叶曲流域、巴塘河流域为低值;河流坡降指数(SL)在流域内整体差异不大,但在水系倒勾状或直角交汇区域的值高;流域高程积分值(HI)在通天河两侧大于0.45,在多采曲—宁恰曲流域、登艾龙曲流域、叶曲流域、巴塘河流域为0.15~0.45。地形、水系和地貌指数的分布特征表明该地区水系可能原为南东流向的平行水系,后期由于走滑断裂剪切作用导致河流改向、袭夺而演化为倒勾状水系。其中当江、立新乡、隆宝镇、上拉秀乡北部等地区断陷形成局部积水中心,而通天河南西—北东向细小支流如宁恰曲等由于断层东北向的逆冲抬升而溯源侵蚀加强,袭夺了原南东流向的河流。

关键词: 新构造活动, 倒勾状水系, 河流袭夺, 走滑断层, 通天河, 青藏高原

Abstract:

The Tongtian section of the Yangtze River is located in ??the central part of the Tibetan Plateau where the neotectonic activity is illustrated by frequent earthquakes, such as the Yushu earthquake (Ms 7.1) on April 14, 2010. The study area is situated in the upstream parts of the Yellow River Basin, the Yalong River and Lanchang River catchments. In this region the tributaries have developed an inverted drainage pattern with nearly right-angle intersection. Based on terrain and areal river system analysis, including geomorphic index calculation, this paper discusses the evolution of the drainage pattern related to the neotectonic movements in this area. Two groups of valleys are distinguished with NW-SE and SW-NE directions, respectively. The NW-trending rivers are unfit channels with gentle slope and large width, while most of the SW-trending rivers are canyons with steep slope and V-shaped transect. It turns out that the steepness index (ks) in the southeastern part of the Tongtian River is higher than that in the Duocai-Ningqia basin, Dengailong basin, Yequ basin and the southwestern part of the Batang basin. The stream length-gradient index (SL) is similar in the whole catchment, but the SL values in the inverted channels and nearly right-angle intersecting channels are abnormal. The value of the hypsometric integral (HI) is over 0.45 at both sides of the Tongtian River, while it is 0.15-0.45 in the Duocai-Ningqia basin, Dengailong basin, Yequ basin and Batang basin. The values and distribution of geomorphic indexes indicate that the pre-existing SE-trending parallel-drainage pattern turned to an inverted-drainage pattern as a result of strike-slip faulting. Dangjiang, Lixing, Longbao and the northeastern part of the Shanglaxiu regions became pull-apart basins, while the tributaries of the Tongtian River in the northeast eroded dramatically headward as a result of the uplift of the NE-trending thrust, and finally captured the former SE-trending channels.

Key words: neotectonic movement, inverted drainage pattern, river capture, strike-slip fault, Tongtian River, Tibetan Plateau