祁连山北麓地貌信息熵与山体演化阶段分析

Analysis on the geomorphic information entropies and the evolution of the Qilian Mountains

利用定量化的手段分析地貌演化的阶段和趋势,是地貌学研究领域的一个重大的理论课题。在地理信息系统软件ArcGIS和ArcView的支持下,利用数字高程模型提取祁连山北麓的河网和流域。利用Strahler积分计算了各个流域的地貌信息熵,按照主夷平面的高度将祁连山北麓的各个流域分为不同的部分,它们具有不同的地貌信息熵值。结果显示,祁连山地区正在进入戴维斯侵蚀旋回的幼年期阶段。

Analysis on the geomorphic evolution is a principal theoretical proposition in Iucubrating geographical issues, from a view point of system, geomorphic information entropy is a helpful index for lucubrating geographical issues, The average elevation of the Qilian Mountains varies in a range of 4000-5000 m a,s.l., and the elevation of many peaks is over 5000 m. The mountainous regions above 4100 m are perennially covered by snow, many modem glaciers are developed, and many rivers rise there, The areas of the gentle-sloped （〈 10°） regions and steep-sloped （〉30°） regions occupy 40.52% and 11.33 % respectively. In the Qilian Mountains, there are two planation surfaces and one erosion surface, i.e., the mountaintop surface, main planation surface and erosion surface, which are regarded as the direct indications of episodic and dramatic uplifts of mountains, therefore they have the important significance for inferring the ages of mountain uplifts, Based on the data of vector topographic map, in this paper the geomorphologic evolution stages of 14 drainage basins in the Qilian Mountains are studied with aid of ArcGIS and ArcView, According to the altitude of the planation surface in the Qilian Mountains, we derive the respective geomorphic information entropies and the different Strahler integral curves of the three segments of the drainage basins. The average geomorphic information entropies of the regions vary in a range 0.13-0,39, most of the entropies above the main planation surface exceed 0.4, and the entropies under the main planation surface are all less than 0.2. The geomorphic information entropies reveal that the study areas are undergoing a transition from old stage to young stage ofgeomorphologic evolution.