Two-stage exhumation, uplift, and basinward propagation of the Tian Shan during the late Cenozoic

Abstract

As a typical intracontinental orogenic belt, the Tian Shan is a natural lab for the understanding of ongoing intraplate deformation and related geodynamic mechanisms. Knowledge of the spatial and temporal patterns of uplift and exhumation of the range can provide critical insights into this issue. This work used apatite U-Th/He thermochronological analysis and river profile inversion to reveal the histories of exhumation and uplift of the Sikeshu catchment, northern Chinese Tian Shan. Also, the spatiotemporal variations in the rate of exhumation across the Tian Shan were investigated, by inverting from a dataset of 1817 compiled apatite and zircon fission track and U-Th/He ages. The results indicated that, the exhumation across the entire Tian Shan primarily began during the early Miocene, with a significant, range-wide enhancement of exhumation occurring around 10 Ma. When combining the independent evidence of mountain uplift from sedimentology, rock magnetism, and structural modelling, we propose a two-stage model of exhumation, uplift, and basinward propagation of the modern Tian Shan, i.e., initial, range-wide rejuvenation around 20 Ma and intensive uplift and rapid exhumation since about 10 Ma. By integrating previous geophysical and geological studies on the Tibetan Plateau, the significantly enhanced exhumation across the entire Tian Shan since ∼10 Ma can be attributed to the Indian-Tarim collision at this age.