摘要:西秦岭位于青藏高原东北缘，是青藏高原晚新生代构造扩展的前缘部位。西秦岭地区发育的一系列河流水系作为高原物质向外扩展的载体，记录了高原扩展过程中的地貌演化信息。本文选取西秦岭嘉陵江上游的支流作为研究对象，以河流纵剖面的形态和陡峭指数的空间分布为基础数据，初步分析了嘉陵江上游的地貌特征及其影响因素。结果表明，嘉陵江上游地貌演化处于瞬时状态，裂点以上的低陡峭指数区域代表了残余地貌，裂点以下高陡峭指数区域是裂点响应基准面下降后形成的新地貌。通过对比区域岩性和降水条件发现，岩性和降水对河流裂点发育以及陡峭指数的影响是有限的，河流裂点的发育和陡峭指数的变化主要受控于区域构造抬升引起的基准面下降。陡峭指数的空间分布特征表明构造作用对地貌发育起了重要的塑造作用。西秦岭瞬时地貌的发育是对印度板块与欧亚板块碰撞汇聚以来的远程效应的响应。
关键词: 嘉陵江上游/
河流纵剖面/
陡峭指数/
地貌过程/
青藏高原东北缘
Abstract:The West Qinling is located at the northeastern Tibetan Plateau, it is the front part of the outward growth of the Tibetan Plateau during the Late Cenozoic. And the fluvial systems developed along the West Qinling, which was resulted from the northeastward expansion of the Tibetan Plateau, had recorded the evolutionary information of landscape during the outward expansion of the Tibetan Plateau. In this paper, the longitudinal profiles of the upper Jialing River Basin and the spatial patterns of normalized channel steepness were analyzed. Based on the geomorphic parameters, we have discussed the general landscape characters of the upper Jialing River Basin and its influence factors. The results indicated that the landscape evolution of the upper Jialing river basin is in a transient state. The upstream basin of knickpoints represent the relict landscapes and downstream basin of knickpoints is the new landscape which is in the process of adjusting to the base-level fall. Local comparisons of the knickpoint development and channel steepness revealed that the lithology and precipitation have limited influence on the knickpoint development and spatial patterns of channel steepness. The knickpoint development and the variations of channel steepness were controlled by the base-level fall which was caused by the tectonic uplift. The spatial patterns of normalized channel steepness revealed that the tectonic force plays a significant role in shaping the landscape. The development of the transient geomorphic in the West Qinling is a response to the remote effects since the Indian plate and Eurasian plate collision.
Key words:Upper Jialing River Basin/
Longitudinal profiles/
Steepness index/
Landscape evolution/
Northeastern Tibetan Plateau
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