GEOMORPHIC FEATURES OF THE HEIHE RIVER DRAINAGE BASIN IN WESTERN QILIAN SHAN-HEXI CORRIDOR AND ITS TECTONIC IMPLICATIONS |
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| Authors: | SU Qi YUAN Dao-yang XIE Hong |
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| Institution: | 1.Lanzhou Institute of Seismology, China Earthquake Administration, Lanzhou 730000, China;2.Lanzhou National Observatory of Geophysics, Lanzhou 730000, China |
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| Abstract: | Using quantitative geomorphic factors for regional active tectonic evolution is becoming more and more popular. Qilian Mountains-Hexi Corridor which locates in the northern edge of Qinghai-Tibet plateau is the most leading edge of the plateau's northward extension. The uplift rate of all segments and the intensity of influence from tectonic activity are the important evidences to understand the uplift and extension of the plateau. Heihe River Basin is located at the northern piedmont of the western segment of Qilian Mountains, the development of the rivers is influenced by the tectonic activity of the Qilian Mountains, and the unique river morphology is important carriers of the regional tectonic uplift.
Geomorphologic indexes such as hypsometric integral, geomorphologic comentropy and river longitudinal profiles were extracted by GIS tools with free access to the Shuttle Radar Topography Mission(SRTM)DEMs, and according to the different expression of the geomorphological indexes in the Heihe River Basin, we divided the drainage basin into two parts and further compared them to each other.
Recent studies reveal that obvious differences exist in the landscape factors(hypsometric integral, geomorphology entropy and river profiles)in the east and west part of the Heihe Basin. The structural intensity of the west part is stronger than that of the east, for example, in areas above the main planation surface on the western part, the average HI value is 0.337 8, and on the eastern part the HI value is 0.355. Accordingly, areas under the main planation surface are just on the contrary, indicating different structural strength on both sides. Similar phenomenon exists in the whole drainage basins. Furthermore, by comparing the fitting river profiles with the real river profiles, differential uplift is derived, which indicates a difference between west and east(with 754m on the western part and 219m on the east). Comprehensive comparison and analysis show that the lithologic factors and precipitation conditions are less influencing on the geomorphic factors of the study area, and the tectonic activities, indicated by field investigation and GPS inversion, are the most important element for geomorphic evolution and development. The variation of the geomorphologic indexes indicates different tectonic strength derived from regional structures of the Qilian Shan. |
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| Keywords: | the western region of the Qilian Mountains DEM Heihe drainage geomorphology tectonic activity |
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