Planation surfaces of the Tian Shan Range (Central Asia): Insight on several 100 million years of topographic evolution

In Central Asia, numerous fragments of planation surfaces are visible within the present day topography. However, their precise timing of formations is still poorly constrained and it is not clear if they are remnants of a single extensive planation surface or if they represent different planation episodes. By reconstructing the landscape evolution of the Tian Shan region and by analyzing the relations between the planation surfaces preserved within the eastern Tarim Basin and the sedimentary record, we demonstrate that the numerous erosional surfaces preserved within the Tian Shan Range represent different episodes of surfaces genesis. These erosion events span from the late Paleozoic to the Early Cenozoic. The widespread preservation of large fragments of these surfaces within the Tian Shan Range implies that this region did not undergo strong relief building during most of its Mesozoic evolution but was dominated by plains associated to small hills along episodically active discrete tectonic structures. Finally, the preservation of these surfaces within the active Tian Shan Range implies a long-term, strong non-equilibrium state of the topography during its Cenozoic evolution. This was probably promoted by the arid to semi-arid climate prevailing since the Late Paleogene onset of relief building.