Cenozoic tectonic rotations in different parts of the NE Pamir: implications for the evolution of the arcuate orogen

Abstract

The Pamir salient, defining the NW end of the Himalayan–Tibetan orogen, is a prominent curved orogen as a response to the Indian-Eurasian collision. Its evolution history is essential for understanding intracontinental tectonic processes in the context of continental collision. In this study, we carry out systematic paleomagnetic studies on four sections in different parts of the NE Pamir to unravel the tectonic evolution of the curved orogen. Our new results from the Oytag section suggest that the clockwise (CW) rotations of the eastern Pamir salient mainly occurred in the Oligocene (~ 32–26 Ma) as a response to the northward indentation of the Pamir salient and was dominated by large-scale dextral strike-slip faults since then. Additionally, the final collision between Pamir and SW Tian Shan in the latest Miocene reactivated the dextral Talas-Ferghana Fault (TFF), thus be responsible for the counter-clockwise (CCW) rotations at Ulugqat. However, the limited tectonic rotations of the Keliyang and Sanju sections can be explained by the dominant thrust faulting in the foreland of the West Kunlun Mountains. Combined with the existing paleomagnetic data around the Pamir salient, our results support a four-stage evolution: (1) a roughly linear orogen before the early Eocene; (2) symmetric rotations on both sides until the latest Oligocene followed by (3) asymmetric geometries with continued radial thrusting on the western flank and large-scale strike-slip fault on the eastern flank; and (4) final collision between the Pamir salient and SW Tian Shan in the late Miocene.