Meso-Cenozoic Evolution Of Dabashan Foreland Basin-thrust Belt, Central China

Sedimentary basin and adjacent orogenic belt are two basic tectonic units of continent and twins developed in a geodynamic system. A foreland basin is connected dynamically with adjacent orogenic belt through a structural belt referred as to fold-thrust belt or thrust belt. Owing to its great significance to continental dynamics and richness in hydrocarbon, the foreland basin-thrust belt system has been paid much attention to in the last three decades. That is the reason why I select Dabashan foreland basin and thrust belt, central China, as my thesis topic.In light of the idea of basin-orogenic belt coupling, I present new structural, sedimentary, subsidence and uplift data integrated into a regional Mesozoic stratigraphic and tectonic framework to provide a detailed picture of spatio-temporal variations in deposition, depocenter migration, and post-depositional deformation of the Dabashan foreland basin-thrust belt system. Moreover, the hydrocarbon potential of the Dabashan foreland basin is also discussed simply in this thesis.The Dabashan fold-thrust belt lies between the northeast Sichuan basin and the Qinling orogenic belt and is a southwestward verging structural belt, joined up with the Hannan-Micangshan dome, Longmenshan thrust belt and Songpan Ganzi complex to the west, terminating at Huangling dome to the east. Tectonically, from orogenic belt towards craton, the Dabashan thrust belt and adjacent region can be divided into three tectono-stratigraphic units by Chengkou fault and Tiexi-Wuxi concealed fault, namely the north Dabashan thrust-nappe belt (N. DBS), the south Dabashan foreland fold-thrust belt (S. DBS), and the Sichuan basin. The deformed north Sichuan basin and S. DBS constitute the Mesozoic Dabashan foreland basin (Late Triassic to Early Cretaceous) discussed in the thesis.The north Sichuan basin, together with the S. DBS, behaved as a passive margin south of the Qinling Tethys from late Paleozoic to Middle Triassic times and then evolved into a foreland basin in response to the amalgamation of the North and South China blocks along the Qinlig-Dabie orogenic belt since the late Late Triassic. Since the middle to late Early Cretaceous, with the edge of the South Qinling deformed belt advancing toward the foreland through time, previously-deposited proximal strata in the Dabashan foreland basin were deformed in the leading edge of the thrust belt, and then uplifted and eroded by subsequent subaerial processes. The subsidence of Dabashan foreland basin and coeval basin-margin compressional deformation from northeast to southwest during Late Triassic to Cretaceous times occurred after the westward progressive collision of the South China Block with North China Block, suggesting that the orogenic and basin-forming events were intracontinental in nature.The N. DBS is characterized by brittle-ductile deformation and basement-involved structure, composed of a suite of thrusts and associated asymmetric folds directed southwest. The S. DBS is a thin-skinned thrust wedge superposed by dextral transpression, characterized by brittle deformation and Jura-like folds, including box fold, tight overturned-isoclinal fold, and complex closed fold. The...