Tectonic Evolution Of The Yidong Fault Zone And Its Relationship With Sedimentation

As one of important boundary faults in Zhanche area,Jiyang depression,the Yidong fault zone has been researched and explored for many years,which has obtained remarkable achievements.However,the fault still needs some unified understandings in terms of its formation mechanism,evolutionary characteristics and the relationship between fracture activities and sedimentation.This manuscript firstly combines current geological materials with seismic interpretations to definite tectonic characteristics of the Yidong fault zone and its adjacent areas,then uses techniques like evolution profiles and thickness analysis to analyse evolution features of the Yidong fault zone qualitatively and quantitatively on the basis of fault characteristics.Combining acquired evolution features with tectonic stress fields and depositions of various periods to do thorough researches in forming mechanisms of the Yidong fault zone and its impacts on sedimentation.Besides,the study also does some analysis and predictions on oil and gas distributions and resource potentials for the Yidong fault zone and its adjacent areas.New understandings of several aspects are obtained from the research.As for the fault evolution,the Yidong fault zone experiences totally four stages from its formation to its extinction,namely starting stage?E₁k-E₂s₄?,active stage?E₂s₃-E₃s₂?,reducing stage?E₃s₁-E₃d?and dying stage?Ng-Nm?,the general trend on fault activities alongside the strike of the Yidong fault zone is that the fault activity intensity in the southern part of the Yidong fault is stronger than the northern one.For dynamic features,the Yidong fault zone is a dextral strike-slip fault forms in the shearing stress field of the early Cenozoic,it becomes active since the conversion of tectonic mechanisms in the forth section of the Shahejie formation.The fault zone changes into the oblique extension fault with natures of both extensional and strike-slip faults,showing characteristics of growth faults during the sedimentary stage from the third section of the Shahejie formation to the Dongying formation.For the tectonic-sedimentation,the fault activity shows remarkable controlling in sedimentation during the sedimentary stage from the late fourth member in the Shahejie formation to the second member in the Shahejie formation.Clastic provenances in the Yihezhuang uplift choose positions which have relatively low fault activities intensities to inject into the Sikou sub-sag,forming deposits of sand-bodies.The fault slope break,the transition structure and the changing of fault activities alongside the strike all produce impacts on inputs and sedimentation of sand-bodies.Erosion areas are covered by carbonate deposits after the first member in the Shahejie formation,fault activities do not influence sedimentation.In the aspect of oil and gas,oil and gas resources distribute in every sedimentary stage when the Yidong fault zone develops and the southern fault has more abundant reservoir types compared with the north.Shallow layers has good resource potentials,northern newborn faults and residual erosion areas in the southern Yihezhuang uplift all promote the development of oil and gas reservoirs.