Abstract:

Longmen Shan is located at the boundary between the Sichuan Basin and the eastern margin of Tibetan Plateau, representing the steepest gradient of any edges of the plateau. Its uplifting process and mechanism are important scientific issues studied by international geologists. Especially after the large amount of denudation such as landslides and debris flows since Late Cenozoic, Longmen Shan did not reduce the elevation, but continually uplifted. This article discussed three popular geodynamic mechanisms about Longmen Shan tectonic uplift in Late Cenozoic, i.e. channel flow in the lower crust, crustal shortening deformation and crustal isostatic rebound. The uplift of Longmen Shan in Late Cenozoic is related to isostatic rebound associated with erosion. The erosion denuded crustal rocks gradually, and the space occupied by the original erosional material was replaced by air, which led the lithosphere or crust to produce negative load and caused uplift of the mountain. Combining with digital elevation model data, this research revealed that the coseismic deformation caused by repeated large seismic events and isostatic rebound induced by rapid surface erosion, such as earthquake, landslide and debris flow, might be a new geodynamic mechanism to drive ongoing mountain building of Longmen Shan. The elevation of Longmen Shan nowadays may be controlled by tectonic and erosion-induced isostatic rebound effects, and the contribution of erosion-induced isostatic rebound on the uplift of Longmen Shan is about 30%.

Key words: Longmen Shan, uplift, erosion, isostatic rebound, digital elevation model