Provenance and deformation style of lower Cretaceous sedimentary rocks in Huangcheng basin, northeastern Tibetan Plateau

The sedimentary rocks in the Hexi Corridor, north-eastern Tibetan Plateau, contain information about crustal deformation during and after the closure of the Meso-Tethys Ocean and the growth of the Tibetan Plateau. This study examines the origin and deformation of Late Mesozoic sedimentary rocks in the Huangcheng basin where the source of Late Mesozoic sedimentary rocks and deformation styles of faults and folds remain controversial. Results from field mapping, fault kinematic analysis, and detrital zircon analysis suggest that the study region might have experienced three episodes of compression events since 100 Ma. The first episode is characterized by north-south compression, which could reflect the convergence between the Alashan and the Qilian Shan -Nan Shan. The second episode reflects the reactivation of the thrust faults related to the far -field effect resulting from the closure of the Neo-Tethys Ocean. The third episode is the regional east-west trending thrust due to the block extrusion. One set of slickensides indicates north-south compression while a second set implies nearly east-west compression, which could represent different stress orientations between the first two episodes and the third episode. Eleven detrital zircon samples from the Cretaceous to Neogene strata were collected for detrital zircon U-Pb dating and rare earth element analysis. Zircon U-Pb ages show major peaks around 265 Ma and 455 Ma with a notable lack of ages around 1.0 Ga. We infer that the source of the Neogene sedimentary rocks was the Qilian Shan while the sources of the Cretaceous sedimentary rocks were the Qilian Shan and Alashan.