Formation and modification history of the Liupanshan basin on the southwestern margin of the Ordos block and tectonic stress field evolution

Abstract：Sandwiched between the Ordos block and the Alxa and Qinghai-Tibet blocks, the Liupanshan basin is situated in a special tectonic location in the tectonic system of China. Based on the field analysis of deformation and stress field inversion from fault slip data, the formation and tectonic evolution history of the Liupanshan basin has been preliminarily established. The results show that the basin mainly experienced the stage of basin formation and the stage of modification in the late stage. During the earliest Cretaceous, under the nearly E-W extensional stress, the basin was downfaulted and a very thick fluvial-lacustrine sequence of the Liupanshan Group was deposited in the basin. Near the end of the Early Cretaceous, under the NW-SE compression, the Liupanshan basin was inversed with in fold inversion occurring in some places, and the Liupanshan Group underwent faulting and deformation to different degrees. Then the basin began the long-continued uplift and erosion history. During the late Cenozoic, under the far-field effects caused by India-Eurasia collision, the Liupanshan basin was strongly folded and faulted due to NE-SW compression and then due to E-W compressions and Liupanshan was uplifted rapidly. The evolutionary history of the Liupanshan basin and change in stress regimes during the Early Cretaceous provide constraints on the geodynamics of block interaction in this area and are of importance for oil and gas exploration.