DEM-based Surface Processes Analysis For The Northeast Margin Of The Tibetan Plateau

The Northeast margin of the Tibetan Plateau is the front of the Tibetan Plateau expanding to the inner of the Asia continent. The particular landform and the evolution processes of this area indicate the deformation history of the Tibetan Plateau and the environmental change information as well.To investigate the interplay between tectonics, lithology, climate and the topography of the orogen plateau, the geomorphological parameters are extracted based on SRTM DEM data. Combined with geological data, remote sensing data and the climate data, the relationship between topography, tectonics, lithology and the climate has been quantitively analysed. Based on the characters of the landscape, 2 topographic zones have been divided. We suggest that the eastern zone which characterized by a descending topography from SW to NE is the outcome of the NE-SW oriented tectonic deformation propagation to the foreland which derive from the Indian-Asia collision. A joint process of climate, tectonics and the regional gravity isostasy plays an important role on the forming of the flat western topographic zone.Paleosurface reconstruction is one of the new techniques for the study of the surface processes. It shows that after the deposition of the Miocene strata, the study area has undergone an intensive tectonic uplift. The results of the erosion quantity in Holocene of the Xunhua-Guide-Gonghe basins show a decreasing trend of the erosion rate to the headwater. The increasing of the base level to the upstream caused the continuous weakening of the erodibility.The low relief erosion surface is formed during a long time of tectonics inactive period. Two erosion surfaces have been extracted in the study area. 2nd erosion surface is located in the SW of the study area. The crustal thickening caused by intensive uplift is the main reason for the higher elevation of this erosion surface. While 1st erosion surface distributed mainly on the Cenozoic strata, the high erodibility of the lithology may caused the lower elevation of this surface. Several large rivers formed in late Quaternary, the headwater erosion of these rivers have not reached into the 2nd erosion surface. Thus, the 2nd erosion surface is more complete than the 1st one.River recorded the tectonics information of the oroganic plateau. A series of DEM based river analysis has been done to discuss the reason for the drainage parameters differences. The rapid uplift of the mountain range in the east of Min County interrupted the paleo Tao River, later on, the river from the northeast cutting through the West Qinling Fault zone by headwater erosion, finally captured the paleo Tao River near Min County and formed the new Tao River.DEM based surface processes study is a new technique to study neotectonics. The techniques and the theory are still in developing. This research investigated some new thoughts and methods and attempts to provide reference for understanding the complexity between Surface Process, Tectonics and climate.