Spatiotemporal development of Cenozoic tectonic deformation in the Qilian Shan, northeastern Tibetan Plateau: A review of low-temperature thermochronologic evidence

The growth of the Tibetan Plateau governs Asian tectonics, geomorphology, and climate change in the Cenozoic. The Qilian Shan is a fold-and-thrust belt that defines the northeastern boundary of the Tibetan Plateau. The spatiotemporal evolution of Cenozoic crustal deformation in the Qilian Shan is crucial for revealing the growth process of the Tibetan Plateau and its dynamic mechanisms. Mountain deformation can be revealed through basin sedimentology but is limited by vastly disputed stratigraphic chronologies. Low-temperature thermochronology provides independent dating to reveal deformation-induced exhumation. We provide new and reviewed published low-temperature thermochronologic data from in situ bedrock in the Qilian Shan and from sedimentary detritus in the surrounding basins. The results indicated that the Qilian Shan experienced two phases of enhanced exhumation, one in the Eocene and one in the Miocene. Early Eocene crustal deformation of localized structures in the Qilian Shan was a rapid tectonic response to the Indian-Asian plate collision. Intense and extensive crustal deformation since the early Miocene has been accompanied by shifts in regional tectonic regimes. The Eocene deformation did not follow the present structures, but the Miocene deformation did, indicating that the present structural framework generally formed during the Miocene. This review shows that the Qilian Shan has experienced two phases of temporally and spatially differentiated tectonic deformation since the early Eocene and early Miocene. The Qilian Shan has been the northeastern structural boundary of the Tibetan Plateau since the early Cenozoic.