The Deformation Mechanism Of The Tectonic And The Study Of Its Sand Box Analog Models In Xujiaweizi Fault Depression

Base on the regional geological data and three dimensional seismic data,this dissertation reinterpretate the key seismic profiles with new interpretation schemes.based on the study of the geometrical characteristics of the faults,combining the tectonic evolution stage and the tectonic setting of the region,the period of faults activity is determined.The balanced cross section technique is used to analyses the tectonic evolution of work area and the genetic mechanism.Using the analogue modelling to simulate the main faults durting syn-rift stage and the tectonic evolution process of Xujiaweizi Fault Depression,which can provide evidence of the analysis of the genetic mechanism.Three main fault were developed in the Xujiaweizi Fault Depression,F1 F2 and F3.F1 and F2 were boundary faults,and F3 is considered to be a transfer fault between F1 and F2.F1 and F2 have multiple strike on the plane,as well have the segmented growth feature,which feflect that study area has been experienced multiphase and multi direction deformation,stratigraphic deposition controlled by the boundary fault.The tectonic evolution stage of Xujiaweizi Fault Depression can be divided into 5 stages: the basement forming stage during the late Plaeozoic to early Mesozoic(Pre-rift stage),the sedimentary period of the Huoshiling formation in the Mesozoic is the initial rifting stage,the sedimentary period of the Shahezi formation is the strong rifting stage of basin.After the Shahezi formation deposited,Xujiaweizi rift enter the shrunk stage of rift,and the post-rift was considered to be the late Denglouku formation.According to the geometry and kinematics characteristics of the fault,It is considered that there are several tectonic stress orientation in Xujiaweizi rift,during the period of Huoshiling formation,the direction of extensional stress is near EW direction,the period of Shahezi formation is a strong rifting stage,the direction of regional extension stress is EW.At the end of the Shahezi formation,due to the influence of near EW compression stress,the depression enter the shrunk stage of rift.The extension stress of 1st member of Yingcheng Formation is NW direction,but the strength of the rifting is obviously reduced and at end of the 1st member of Yingcheng,the stress is EW reversing.The direction of regional extension strss in the 3th member of Yingcheng is NW,and this change of the direction leads to the fault and formation distribution are different from the previous stages.Using the analog models and the banlanced section technique,it is considered that the structure evolution of Xujiaweizi Fault Depression has experienced multiple periods of extrusion and stretching deformation in many direction.The structural deformation process of Xujiaweizi Fault Depression can be simulated by using several rigid base blocks to establish the base model.The experimental results show that the multi period and multi-direction extension and compression deformation transformation make the structure of the syn-rift period complex.Under the control of the pre-existing structure,the fault depression mainly developed two boundary fault,F1 and F2,the type of fault was listric nomal fault or ramp-flat normal fault,and the F3 fault was developed between F1 and F2,it is controlled by the pre-existing structure,and it was produced by multiple tensional torsion and compressive torsion.Not the pure strike slip fault that considered by the predecessors.