Structure and provenance of the Cretaceous Pingshanhu Basin in the Hexi Corridor: Implications for Mesozoic tectonics in the northern Tibetan Plateau

The construction of Earth's largest highland, the Tibetan Plateau, is generally considered to have been generated by the Cenozoic India- Asia collision. However, the extent to which high topography existed prior to the Cenozoic remains unclear. The Hexi Corridor foreland basin of the northern Tibetan Plateau is an ideal region in which to investigate this history, given its widespread exposure of Early Cretaceous sedimentary sequences. In this study, we examined the Early Cretaceous strata in the northern Hexi Corridor to understand the relationships between pre- Cenozoic sedimentation and tectonic deformation and constrain the late Mesozoic tectonic setting of the adjacent Qilian Shan and Alxa blocks bordering the northern Tibetan Plateau. Results of sandstone petrology analyses, paleocurrent observations, and U-Pb geochronology suggest that the oldest Early Cretaceous sediments deposited in the northern Hexi Corridor were sourced from the southern Alxa block during the earliest Cretaceous. By the late Early Cretaceous, Hexi Corridor sediments were sourced from both the southern Alxa block to the north and the Qilian Shan to the south. Sandstone petrologic results indicate that the northern Hexi Corridor experienced a tectonic transition from contraction to extension during the Early Cretaceous. These findings suggest that the northern Tibetan Plateau region was partially uplifted to a high elevation during the late Mesozoic before the India- Asia collision.