THE TOPOGRAPHIC EXPRESSION FEATURES OF THE MINSHAN TECTONIC BELT ALONG THE NORTHEASTERN MARGIN OF THE TIBETAN PLATEAU: A DEM-BASED PRELIMINARY RESEARCH

The topographic expression of the eastern margin of the Tibetan Pleteau is the most complex compared with the northern and southern boundaries. Together with the Longmenshan Range southward, the Minshan Ranges is the middle territory of the eastern boundary by the square. Since the Cenozoic, accompanied with the intense uplifting and erosion of the plateau, these basin and range systems also have been experiencing multistage tectonic activities. In tectonic and geomorphic view, the Minshan Tectonic Belt (MTB) is the right linkage between the Tibetan Plateau, the Sichuan Basin and the West Qinling Ranges. But the prevenient researches mostly dealt with the tectonic evolution and geomorphic characteristics of the Longmenshan Tectonic Belt (LTB) and the Minjiang Fault Zone (MFZ); moreover, the time limits of their studies on the tectonic evolution were bounded within the Mesozoic and the Quaternary. Now that the MTB and adjacent region are the key continental escarpments along the eastern Tibetan Plateau, the geomorphic characteristics of the topographic expression will have some interesting indications for the Cenozoic activities. Based on the analysis of the digital elevation model (DEM) derived from digitizing the contour line, this paper aims to preliminarily discuss the geomorphic characteristics of the MTB, such as the drainage pattern and the mutual relations among the lithology, the structure and the topography. The study indicates that the Minshan Tectonic Belt, as the northeastern margin of the Tibetan Plateau, has distinct characteristics of its topography. These characteristics have a tight relation to the structure and the stratigraphical lithology. Additionally, the drainage divide of the Yellow River and the Yangtze River is yielded mainly because of the lithological difference; however, in the Yangtze River drainage, the differential uplifting during the Cenozoic controls the patterns of the drainage networks.