Tectonic characteristics and their shale gas geological significance of the Mesozoic-Paleozoic in Jiaoshiba area,the Sichuan Basin
She Xiaoyu, Chen Jie, Zhang Shiwan, Shu Zhiguo, Yu Fei, Li Dongdong, Gong Xiaoxing
2016, 37(6):
828-837.
doi:10.11743/ogg20160604
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Through 2D and 3D seismic interpretation and application of balanced cross section technique,basement structure,and tectonic characteristics and its evolution of the Mesozoic-Paleozoic of Jiaoshiba area,the Sichuan Basin are analyzed in this study.The results show that there are two types of structures in the study area.The first type is basement-involved structure,which is characterized by five structural patterns and assemblages,including back thrust anticlines,ramp syncline,imbricate thrusting,positive flower wrench and "多"-shaped wrench.The other type is cap detachment structure,which is characterized by five structural patterns and assemblages,including fault-propagation or fault-bend,fault-slipping,imbricate thrusting,imbricate ramp and thrust wedge.Additionally,the Early and Middle Yanshanian period are two major tectonic deformation periods.During the Early Yanshanian period,the nearly horizontal westwards detachment and decollement-nappe structures occurred along the interface between the Mesozoic-Paleozoic and the basement and the interfaces within the basement,resulting in the anticline-syncline alternating Zhuluoshan fold.The Jiaoshiba area between Fangdoushan fault and Datianchi anticline is within a broad compressional synclinorium structural background.During the Middle Yanshanian period,the detachment of the middle-deep burial basement in the eastern trough-like fold belt caused intensive westward thrusting,and then led to the formation of the tectonic framework of obduction-thrust-overthrust in the Jiaoshiba area.The double-layer back-thrusting anticline and faulted fold belt in the flanks were formed in Jiaoshiba area after three deformation episodes,including basement-involved imbricate thrusting-cap rock decollement-left-lateral transpression.Furthermore,Shimen faulted fold belt is characterized by multi-layer detachment folding structure and Wujiang fault-fold belt is characterized by detachment and left-lateral transpression structure.The tectonic deformation properties and types,decollement degree of the Longmaxi and Wufeng Formations,and layer-slipping structural fractures are the major tectonic factors controlling the shale gas play.