The Structural Characteristics And Evolution Of Talaha Fault Zone,Songliao Basin

The major part of Talaha fault zone locates in the Longhupao—Daan terrace in a secondary unit of Songliao Basin,on which three basement fractures including Xiaolinke fracture,Aogula fracture and Talaha fracture were developed.The Talaha fault zone is composed of a series of small faults formed in the later period above the basement fracture.In this work,the Talaha fault zone had been studied by means of basin analysis,tectonics analysis,sedimentology and balanced cross section based on 3-D seismic data and drilling data.In this research,Talaha fault zone had the characteristics of multi-stage tectonic movement and structural superimposition.In the final sedimentation period of the first member of the Qingshankou Formation,the research area experienced a stretch tectonic movement in the NEE-SWW direction,resulting in the formation of a series of Kqnl,faults in the direction of NNW-SSE as well as the Talaha fault zone.In the final sedimentation period of Yaojia Formation,the research area experienced an minor stretching extension,during which the formed Kqnl faults again experienced movements.In the sedimentation period of upper member of the Nenjiang Formation,the Talaha fault zone experienced a weak stretching movement in the direction of NW-SE and a strong compressive tectonic movement in the direction of NW-SE,led to the formation of a series of reverse faults and folds in the direction of NE-SW.Another relatively strong stretching movement in the NW-SE direction and an inversion tectonic movement took place in the final sedimentation period of Mingshui Formation.The formed normal faults and inversion folds systems superimposed on the structural deformations in the final sedimentation of the 3rd and 4th member of the Nenjiang Formation,resulting in the present fold style in the direction of NE-SW.In late Cenozoic,the north part of research area experienced a stretching in NE-SW direction and a weak inversion tectonic movement in NE-SW direction.Besides,we also found that the structural characteristics of basements had significant impacts on the formation and evolution of shallow layer structures.First,the smaller the angle between the structural trend of the basement and the principle strain direction in the final structural movement,the more significant impacts the basement structural characteristics will have on the final structural movements.When a certain angle existed between the structural trend of the basement and the principle strain direction in the final structural movement,a deviation was always found between the actual direction of structural deformation and the theoretical direction of deformation.Secondly,under the effects of the final tectonic stress,the newly formed structures always locate on the weak zone of basement structures.Thirdly,the different medium of basements had different influences on the final deformation movements.When the basements were rigid medium,the final structural movements were more likely in the formation of faults or detachment surfaces.While when the basements were plastic medium,the final structural movements were more likely in the formation of flow or fold deformation.