Structural style and deformation mechanism of the southern Dabashan foreland fold-and-thrust belt, central China

摘要: The Daba Mountains define the southern margin of East Qinling orogenic belt, and form boundary Sichuan basin in north northeast. can be divided into two structural belts by NW-striking Chengkou fault, namely northern Dabashan thrust-nappe belt foreland fold-and-thrust belt. is a southwestward extruding thin-skinned thrust wedge, showing obvious belted change deformation style intensity along dip direction, further three sub-belts, i.e. imbricate sub-belt characterized stepped-thrust sheets, thrust-fold combination equally-developed thrusts related folds, detachment-fold box folds closed overturned-isoclinal on outcrops. Several kinds structures have been recognized or inferred, including system, passive-roof duplex (triangle zone), fault-related back-thrust system pop-up structure. NE-SW compressive stress from detachment layers covering strata are most important determinants style. After collision between North China block Yangtze at end Middle Triassic, northward intracontinental subduction edge was initiated, which led to corresponding southward thrusting upper crust. propagated towards through Jurassic extended southernmost part around Early Cretaceous, with preferentially developed major progressing upwards Lower Sinian Cambrian Silurian Middle-Lower Triassic.