49 A Dem-Based Geomorphology Analysis in the Xunhua-Guide District, China
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Xunhua-Guide area is located in the middle-east part of the northeast Tibetan Plateau, and its relief is characterized by step-shaped low-relief at different elevation. In this paper, we argue the optimum filter window size of local relief which is 450m×450m, and discuss the geomorphological characteristics of Xunhua-Guide district based on numerical analysis of a digital elevation model (DEM), such as mean elevation, summit and base, as well as local relief and mean slope, from a high quality digital elevation model data. The largest relief is localized along the plateau's mountain rim, and mainly associated with active faults. It is characterized by low values of local relief which are related to sediment-floored flats and the deeply incised valleys prevailing in the low elevations and planation surface in the high elevations. The geomorphological features in Xunhua-Guide area indicate that the northeastern Tibetan Plateau under went a growing process of thrust uplift and the foreland basin vertical aggradation from the Oligocene to the early Pleistocene and regional tectonic uplift and river deep incisions after middle Pleistocene.