Kinematic Characteristics Of Main Faults In Tazhong Uplift Of Tarim Basin

The development and evolution of the main faults in the Tazhong uplift dominated the structure of uplift,the sedimentary development and oil and gas reservoirs with the different types during the different phases.It is always difficult problems and hotspots including the active times,the kinematics and dynimics of the main faults.Based on the previous researches,this paper comprehensively uses the drilling data,2D and 3D seismic data to study carries out the core-observation,and reinterpretes seismic profile data.The features of the fault systems in Tazhong uplift,especially the main faults including the Tazhong No.1,the Tazhong No.2,the Tazhong No.10 and the Tazhong No.5 fault belts are analyzed.The geometric characteristics and the spatial-temporal differences of these faults are described.The structural deformations during the different times are reconstructed using 2Dmove software and fault-bend fold modles.And the tectonic movement periods have been analysed by vertical and lateral motion displacements and average velocity at different stages.The kinetic characteristics of the main faults are described qualitatively and semi-quantitatively.The activities of the fault system in Tazhong uplift early Paleozoic are also revealed by recognizied seismic records in well cores.The faults formation evolution and kinetics are discussed.The research has made the following understanding:(1)the faults system in Tazhong uplift is complex,they are mainly thrust faults with the strike-slip faults and normal faults.The fault strikes are diversity.The NW-trending faults and NE-trending faults existed and with nearly SN-trending small fault groups.The activities of the main faults were in multi-periods,and their properties were changable.(2)The reconstructed geological sections of the tectonic movement periods,they show that the Tazhong No.1 fault and Tazhong No.2 fault mostly initiated in the late Neoproterozoic with normal faulting,and lasted to the Middle Ordovician or Late Ordovician,at the end of the Late Ordovician they changed to reversed faults.The main faults activities were stronger in the eastern and southern parts of the Tazhong Uplift,especially the activities were stronger during the late Ordovician,SilurianMiddle Devonian,late Devonian-Carboniferous.(3)The single-stage perpendicular throw,the horizontal shortening and the average shortening rate of the main faults in different periods are analyzed,and represent that they are significant difference during differrent stages.During the Late Ordovician,the perpendicular throws and the horizontal shortening were larger,and the southern part was stronger in the whole uplift,the most perpendicular throws was 850 m in the east segment of Tazhong No.2 fault,the most horizontal shortening attained 6.0 km.During the Siliurian to Middle Devonian,the east segment of Tazhong No.1 fault and middle of the Tazhong No.2 actived intension,the most horizontal shortening was 1.7 km and perpendicular throw was 330 m respectively.During the Late Devonian and Carboniferous,Activities of the Tazhong No.1 and Tazhong No.10 had weakened or stopped,the Tazhong No2.and No.5 faults were reactivated,whith the 0.2 km for the largest horizontal shortening and the 460 m for the perpendicular throw of the Tazhong No.5 fault.(4)Multiple sets of soft sedimentary deformation structures are identified,and the structural types of "Complex plunged sediment mixtures" are discriminated.Combined with seismite discrimination criteria and characteristics of regional tectonic developments,seismic records and sequences are analyzed,which reflect the tectonic events of high-resolution with pulsation and circularity during the tectonic movement periods.(5)The different stage kinematic characteristics of the main faults in Tazhong uplift,responsed with the tectonisms in the margin of basin and the deep of the basin during the different phases.May be related to the Southern Altyn Ocean and the West Kunlun Ocean closed in the late period of Eopaleozoic,the Northern Altyn Ocean and the south-part of southern Tianshan ocean closed in the late of the Middle paleozoic and the activities of the Kangxiwar Faults of South Kunlun terrane in Late Paleozoic.The development of the main faults in Tazhong uplift reflects the multiple phases and difference tectonisms superimposed effects on the uplift.