The Late Cenozoic crustal shortening in the north‐east margin of the Qilian Shan: Evidence from the Fengle Basin, Gansu Province

Abstract

The north‐east margin of the Qilian Shan forms the front of the northeastward expansion of the Tibetan Plateau. Its Cenozoic crustal shortening is significant for understanding the uplift and growth of the Tibetan Plateau. The Fengle Basin, in the north‐east margin of the Qilian Shan, is characteristic of the typical regional superimposed deformation in Cenozoic strata, documenting the Cenozoic tectonic evolution process in the north‐east margin of the Tibetan Plateau. In this study, we conducted large‐scale geological mapping and regional structural analysis in the Fengle Basin, and rebuilt the two phases of Late Cenozoic crustal shortening deformation in this area: (a) The NW–SE shortening deformation in the Middle–Late Miocene led to the formation of NE‐striking folds in the Fengle Basin, and a hiatus between the Lower and Upper formations of the Gansu Group, probably linked with the far‐field effect of the northwestward subduction of the Pacific Plate. (b) The NE–SW shortening in the Late Miocene–Early Pleistocene overprinted the early NE‐striking folds, resulting in the development of a large‐scale dome structure in this area. The NE–SW shortening is associated mainly with the northeastward growth of the Tibetan Plateau. This study provides crucial evidence for the reconstruction of the intracontinental deformation process in the northeastern periphery of the Tibetan Plateau.