Distinct Orogenic Processes in the South- and North-Central Tien Shan from Receiver Functions

Uplifting mechanisms for the Tien Shan, an active intracontinental orogenic belt, have been under debate for decades, a key issue being how the convergence has been accommodated at depth. Here we investigate the Moho structure across the central Tien Shan by common-conversion-point imaging and H-k-c stacking of receiver functions from a dense array. The observed Moho exhibits distinct characteristics among sub-blocks. Southward-dipping diffuse Moho is imaged in the Southern Tien Shan (STS), in contrast with the relatively flat and sharp Moho beneath the Tarim Basin. This feature along with the large Moho offset beneath the South-Boundary Fault suggests that the shortening and thickening of Tien Shan crust rather than the underthrusting of the Tarim Basin are responsible for the uplift of the STS. In the Northern Tien Shan, however, the imaged Moho doublet provides direct evidence for the underthrusting of the Kazakh Shield accommodating the convergence there.