Abstract:
[Objective] A series of sedimentary basins developed in the Hexi corridor along the northeastern margin of the Qinghai-Tibetan Plateau during the Early Cretaceous. These basins preserve critical records of pre-Cenozoic tectonic evolution in this region, forming the basis for understanding the growth mechanism of the Qinghai-Tibetan Plateau during the Cenozoic. However, the nature of these Early Cretaceous basins remains controversial, hindering consensus on late Mesozoic tectonics in this critical area. [Methods] This study focuses on the Minle Basin in the central Hexi Corridor and carried out a detailed field structural investigation in this area. Through structural analysis and paleo-stress reconstruction, the formation and destruction process of the Minle Basin was redefined. [Results] Our investigation reveals that Lower Cretaceous strata in the Minle Basin contain numerous syn-sedimentary normal faults that strike initially nearly north-south, indicating that the Minle Basin was a fault-bounded extensional basin controlled by nearly east-west extension during the Early Cretaceous. Subsequent deformation is recorded by NE-SW- and NW-SE-trending folds, coupled with shortening structures in Lower Cretaceous strata, indicating NE-SW- and NW-SE-trending horizontal shortening events during the Late Cretaceous. [Conclusion] The Early Cretaceous extension of the Minle Basin was consistent with the widespread extensional deformation and extensional stress direction across East Asia during this period, which was a product of the retreat of the Paleo-Pacific Plate and the consequent mantle material flow. The bidirectional shortening during the Late Cretaceous resulted from the superimposition of the remote effects of simultaneous compression events that developed in the Tethys tectonic domain along the southern margin of the Eurasian Plate and the Pacific tectonic domain along the eastern margin of the Eurasian Plate. [Significance] The deformation mentioned above indicates that the influence of the subduction of the Paleo-Pacific Plate extended westward at least as far as the Hexi Corridor and the northern Qinghai-Tibetan Plateau.