Inversion Of Dadu River Bedrock Channels For The Late Cenozoic Uplift History Of The Eastern Tibetan Plateau

The ongoing convergence and collision between the India and Eurasia Plates has driven the tectonic deformation and continuous uplift in the Tibetan Plateau and adjacent regions.The Tibetan Plateau has a very low relief hinterland with high?relief margins and numerous deeply incised canyons.Local relief of the eastern margin of the plateau is more than 4 km across the Longmen Shan adjacent to the Sichuan Basin.Some previous studies proposed that the topographic relief here is driven by crust shortening due to thrust faulting.However,data from the Cenozoic stratigraphic record and the current GPS velocity field confirmed that the horizontal shortening rate across the eastern Tibet is relatively low and insufficient to construct the modern topography alone.Thus,crustal thickening contributions from viscous middle?lower crustal flow were proposed.The lower crustal flow began at approximately 20 Ma,and at 10–15 Ma the regional uplift was accelerated.Although this inference was supported by growing low?temperature thermochronology studies,the rates of denudation/uplift determined by the thermochronology profiles were often given as an average since a certain time duration.Therefore,it is difficult to quantify the history of tectonic uplift and whether uplift has been uniform or varied through time.The Dadu River in the eastern Tibetan Plateau has the potential to record ransient variations of tectonic uplift since the Late Cenozoic.In this study,we extracted bedrock channels of the Dadu River drainage basin from the 30 m ASTER digital elevation model(DEM).The longitudinal river profiles were then analyzed and three generations of knickpoints were recognized via the slope-area method.By solving the analytical solution of the linear transient stream-power incision model,we determined a late Cenozoic history of regional tectonic uplift.This paper draws the following ultimate conclusions:(1)In the 10 rivers of Dadu River drainage Basin,three generations of typical tectonic knickpoints are identified,and the elevation ranges of the three generationsare 3600-4200 m,2800-3200 m and about 2000 m respectively.(2)The Dadu drainage basin records ?30 Myr tectonic uplift history.Before the Middle Miocene,the relative uplift rate was slow(< 0.1 mm/a),and then increased gradually to 0.33 ± 0.03 mm/a since 15 Ma until present.