Two phases of Cenozoic deformation in the Wudu Basin, West Qinling (Central China): Implications for outward expansion of the Tibetan Plateau

[Display omitted] •Wudu Basin involved into two phases of deformation due to uplift of the Tibetan Plateau.•The early one was resulted from the NNE-SSW shortening during the Late Oligocene.•The late one is reflected by the N-S shortening structures formed at the end Miocene. The Wudu Basin, located in the northeastern margin of the Tibetan Plateau, preserves crucial deformation records for understanding the Cenozoic uplifting and outward expansion of the Tibetan Plateau. Based on detailed geological mapping, we conducted field structural analysis on the geometry, kinematics and dynamics of the Cenozoic structures in the Wudu Basin. Together with regional geology, our study reveal the Wudu Basin has been involved into two phases of shortening deformation during the Cenozoic. The early phase of deformation (D1) is represented by the NWW-SEE syncline developed within the Paleogene strata, as well as the sinistral strike-slipping of the Wudu fault and Luqu-Zhouqu fault. Combining the structural styles and the Eocene strata involved into deformation, the D1 was dynamically resulted from the NNE-SSW shortening during the Late Oligocene. The late phase of deformation (D2) is characterized by a series of E-W striking shortening structures accompanied with the dextral strike-slipping of the Wudu fault and sinistral strike-slipping of the Luqu-Zhouqu fault. As the Neogene strata involved into this phase of deformation, the D2 was attributed to the N-S shortening at the end of Miocene. The D1 records the simultaneously northward and eastward expansion of the Tibetan Plateau in the Late Oligocene, which is consistent with the uplifting in the north-eastern Tibetan Plateau at ca. 28–23 Ma. The D2 of northward compressional structures are most likely corelated with the uplifting along the northern and eastern margins of the Plateau at ca. 8–5 Ma.