地理学报 ›› 2018, Vol. 73 ›› Issue (9): 1702-1713.doi: 10.11821/dlxb201809007

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走廊南山河流纵剖面高海拔裂点的成因

陈苗(),胡小飞(),王维   

  1. 兰州大学资源环境学院 西部环境教育部重点实验室,兰州 730000
  • 收稿日期:2017-11-01 出版日期:2018-09-25 发布日期:2018-09-19
  • 基金资助:
    国家自然科学基金项目(41471009)

The cause of high-altitude knickpoints on river longitudinal profiles along the Zoulang Nan Shan

CHEN Miao(),HU Xiaofei(),WANG Wei   

  1. Key Laboratory of Western China's Environmental Systems, College of Earth Environmental Sciences, Ministry of Education, Lanzhou University, Lanzhou 730000, China
  • Received:2017-11-01 Online:2018-09-25 Published:2018-09-19
  • Supported by:
    National Natural Science Foundation of China, No.41471009

摘要:

河流水力侵蚀物理模型表明基岩河道纵剖面在均衡状态时表现为平滑上凹的形态,其特征反映了构造、基岩抗侵蚀能力和气候的作用;然而自然界河道纵剖面多呈现以裂点为特征的不均衡形态,不均衡的剖面形态以及裂点的研究同样可以对外力作用的变化起到很好的指示作用。位于北祁连的走廊南山高海拔河道纵剖面普遍呈现不均衡形式且发育海拔较高的裂点。通过对裂点成因分析发现,这些裂点并不主要受控于岩性、气候、构造等因素,而反映了冰川作用遗留地形与河流地形的分界。这一结果说明在对河道纵剖面高海拔裂点进行分析时要考虑到古冰川遗留地形也会对现代河道纵剖面产生重要影响,为进一步认识和理解造山带地貌演化以及控制因素提供了思路。

关键词: 河道纵剖面, 陡峭指数, 裂点, 走廊南山, 冰川作用

Abstract:

The stream-power incision model shows that a bedrock channel longitudinal profile is characterized by a smooth, concave-up shape at the steady state, and its characteristics reflect the influences from external forces, such as tectonics, climate, and rock resistance. However, most of the natural rivers present a transient state characterized by knickpoints on longitudinal profiles, which can also infer the influences from external forces. Widespread knickpoints at high altitudes on river longitudinal profiles along the Zoulang Nan Shan (mountain), which is a part of northern Qilian Mountains, provide a particular case for studies on the factor affecting the disequilibrium profile. The analysis of the knickpoints indicates that the formation of the knickpoint at high altitudes is not influenced by lithology, climate and/or tectonics. By comparing the plaeo-glaicial evidences, we proposed that the high-altitude knickpoint reflects the boundary between residual glacier valleys and fluvial channels. The result suggests that we should pay more attention to the inheritance landform by ancient glaciation when analyzing the knickpoint located at high altitudes. This study would greatly increase the knowledge about the geomorphic evolution on high mountain ranges along orogenic belts.

Key words: river longitudinal profile, steepness index, knickpoint, Zoulang Nan Shan, glaciation