| Wuzhishan anticline is located in Mabian area,southwest margin of Sichuan Basin,where neotectonic movement is active.At present,the genetic mechanism and formation and evolution of Wuzhishan anticline are relatively scarce.Based on fault related fold theory and balanced profile technology,this paper makes a comprehensive use of 2D seismic profile,surface geological data and relevant drilling data to explore its shallow and underground structures.The geometric and kinematic characteristics of Wuzhishan anticline are quantitatively analyzed,and the structural evolution history is restored by using the balanced section technology,and the dynamic mechanism of Wuzhishan anticline is studied combining with the structural physical simulation experiment.Finally,we have a clear understanding of the genetic mechanism and evolution process of Wuzhishan anticline.The surface of Wuzhishan anticline is an arc-shaped structure protruding northward.The anticline starts from xinshizhen in the South and goes to northwest;near shengjiping,the structural trend changes from northwest to northeast and converges in Mabian area.The occurrence of the anticline core is gentle,and the occurrence of the two wings is steep.The profile shows an asymmetric "box" anticline.The anticline mainly exposed Permian,Triassic and Jurassic strata.There is no large-scale fault development in the area,only the Lidian fault is developed in the northwest of the anticline,and the indigan dam fault and Zhongdu fault are developed in the indiganba Syncline in the south of the anticline.The fault activity time is relatively new,and most of them are faults since Cenozoic era.To some extent,the surface geological characteristics indicate the neogenesis of tectonic formation.In the 2D seismic section,the characteristics of the same phase axis of different reflectors are obvious,which shows that each layer is basically stable deposition,and better reveals the structure form of the hinterland.Based on the detailed interpretation of seismic profiles,the structural geometry of the hinterland of Wuzhishan anticline is an asymmetric "box shaped" anticline;the layers in the hinterland have similar structural features,and all layers show the characteristics of being involved in structural deformation at the same time.At the same time,there is the same phase axis characteristic mutation interface between the deep basement and the Sinian system.Combined with the structural style of the whole section and the theory of fault related folding,we think that the interface is a fault detachment surface.Comprehensive analysis shows that the formation mechanism of Wuzhishan anticline should be fault decollement fold.In addition,the deep structural characteristics reveal that Wuzhishan anticline is roughly bounded by the lower Cambrian detachment layer,and the upper and lower structural deformation shows great difference,which indicates that the Cambrian detachment layer controls the structural deformation.Based on the comprehensive analysis of geometry,kinematics and equilibrium section evolution history of Wuzhishan anticline,it is considered that the dynamic background of Wuzhishan anticline is the transformation of stress field under the joint action of the northward movement of Indian plate and the uplift of Qingzang Tibet Plateau since Himalayan period,which finally forms the present tectonic appearance.The formation of Wuzhishan anticline can be roughly divided into two stages: the NW trending structure was formed under the action of SW-NE compressive stress in the early Himalayan period,and the left-handed strain system formed by nww-se compressive stress in the late Himalayan period made the NW trending structure arc-shaped and formed the NE trending structure.The tectonic physical simulation experiment has a direct understanding of the formation of Wuzhishan anticline,and better reveals the dynamic mechanism of Wuzhishan anticline,which has reference value for the study of its formation and evolution. |
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