Jurassic Evolution of the Dunhuang Basin and Its Implications for the Early History of the Altyn Tagh Fault, Northeast Tibet Plateau

Basin evolution along the northeastern Tibetan Plateau related to the Altyn Tagh Fault (ATF) has significant implications for deciphering the formation of the Tibetan Plateau. However, the Mesozoic history of the ATF is still not well understood. In this contribution, we present a comprehensive sedimentologic and provenance analysis of the Jurassic Dunhuang Basin (DHB) to reconstruct the basin prototype and evolution and to discuss the early history of the ATF. The basin infill consists of late‐Early through Late Jurassic sediments interbedded with basalt, which were deposited in alluvial to lacustrine environments during the Early to Middle Jurassic, and in fluvial to fan delta environments during the Late Jurassic. The analyses of gravel component, paleocurrent and detrital zircon U‒Pb geochronology indicate that the clastic sediments were mainly derived from peripheral areas of the Bei Shan (north), Altyn Tagh—Qilian Shan (south), and the internal Sanwei Shan. Combined with seismic reflection data interpretations, our results suggest that rifting started by the activation of bilateral boundary faults during the Early Jurassic. This was followed by extension and associated magmatism due to subcrustal ductile necking and increased heat flux during the Middle Jurassic, and by final transformation into subsidence sag related to boundary fault die‐out or weakening during the Late Jurassic. We conclude that the DHB formed in an extensional setting generated by the far‐field effects of the Bangong‐Nujiang Ocean closure during the Jurassic, and that the ATF consisted of three subordinate normal faults rather than a sinistral strike‐slip fault during the Jurassic. Plain Language Summary To understand the Cenozoic rise of Tibetan Plateau, one should pay special attention to the associated Mesozoic basin evolution and its mechanisms. We investigated the Jurassic development of the Dunhuang basin (DHB) by analyzing its stratigraphy, sedimentary facies, and sources. We reconstructed the evolution history of the basin and its Early Jurassic initiation in association with movements along the Altyn Tagh Fault (ATF). Subsequent extension along with increased heat flux during the Middle Jurassic was followed by transformation into subsidence sag in the Late Jurassic. Our results suggest that the DHB formed in an extensional rather than a strike‐slip structural setting, and that there was not sinistral movement along the ATF during Jurassic. Key Points Dunhuang Basin was