Multiple Exhumation Stages During the Cenozoic Evolution of the Northeast Tibetan Plateau

Abstract

The Cenozoic growth history of the northeast (NE) Tibetan Plateau has been strongly debated in the past few years with three deformation models being proposed: progressive northeastward propagation, out-of-sequence deformation, and episodic deformation. Reconstruction of the long-term deformation and exhumation history of the different blocks can help elucidate the growth pattern and tectonic processes involved in the formation of the Plateau. Both the Qaidam and Jiuquan basins—the two largest basins of the NE Tibetan Plateau—contain continuous and well-exposed successions of synorogenic sediments that span the entire Cenozoic. We used apatite fission-track thermochronology, sedimentary facies, and structural and provenance analyses of these successions to determine the exhumation history of the Tibetan Plateau. Five distinct fast exhumation events were recognized and dated: 65–54, 43–39, 34–29, 24–21, and 16–15 Ma. Comparison with existing morphotectonic information enabled us to reconstruct a multiple-stage growth scenario for the NE Tibetan Plateau in the context of the surface uplift phases across the Himalayan-Tibetan orogen during the Cenozoic. Overall, our findings support the episodic deformation model and emphasizes that the current relief of the NE Tibetan Plateau is largely derived from these five of stage of exhumation.