Late Cenozoic Clockwise Rotations in the Westernmost Part of the Arcuate Qiulitage Fold-and-Thrust Belt of Southern Tian Shan Foreland and Its Tectonic Implications

Curvature of fold-and-thrust belts (FTBs) is a rather common feature in foreland basins. The problem of how curves in FTBs originate is essential for understanding the propagation of deformation and tectonic history of orogens. In this study, we carried out systematic paleomagnetic studies in the westernmost part of the Qiulitage FTB, southern Tian Shan foreland, where thrusting, strike-slip fault, and tectonic boundary coexist. Our new results suggest that the study area has been subjected to similar to 20 degrees clockwise rotations after similar to 5Ma. Oroclinal test of the paleomagnetic data across the FTB suggests that oroclinal bending caused by the formation of the curved Qiulitage FTB is the dominate reason for these tectonic rotations. The Kalayuergun dextral strike-slip transfer fault delimiting the western boundary of the Qiulitage FTB is a thin-skinned structure accommodating the discrepancy in horizontal displacement on both sides of it. These results also suggest that the formation of the curved Qiulitage FTB should not be older than similar to 5Ma, indicating that the southern Tian Shan foreland has experienced significant tectonic shortening since the latest Miocene to early Pliocene. Our new results, together with previous studies on deformation history, estimates of crustal shortening, GPS observations and earthquake records, suggest that the southern Tian Shan foreland has been subjected to significant deformation during the past similar to 5million years, and the crustal shortening is still ongoing.