Cenozoic Tectonic Uplift History of Western Qinling: Evidence from Sedimentary and Fission-Track Data

The western Qinling orogenic belt is one of the outermost ranges in the northeastern Tibetan Plateau. Its tectonic uplift history is therefore essential to insight on the evolution history of the plateau. However, the timing of deformation and uplift history is still poorly known. Fortunately, its Cenozoic orogenic history is recorded in an excellent synorogenic sedimentary sequence exposed in the Tianshui Basin, the northeastern foot of western Qinling. According to sedimentary-tectonic analysis of the Yaodian and Lamashan sections based on the previous magnetostratigraphy studies, we speculated that two stages (occurred at 9.2-7.4 and similar to 3.6 Ma) of variation in depositional facies were attributed to the uplift and deformation of the western Qinling, and the modern structure geomorphic frame of the northeastern Tibet formed after 2.6 Ma. Furthermore, four stages of active processes along the western Qin ling occurred at 49-41,34-27,25-19 and similar to 13 Ma, are deciphered from an integrated detrital apatite fission-track data of the Ganquan, Yaodian main sections and seven small ones. The former two are represents the exhumation episodes triggered by tectonism and the others attributed to the volcanic signals.