Fault System And Mechanism Of Axial Area In North Tarim

Tabei uplift experienced a multi-period superposition and transformation of structures,the geological structure and the paleo-tectonic pattern are complex and changeable.Especially in the axis of the Tabei uplift,The long-term development of the fault leads to the strong deformation of the strata.The fault system in different periods affects the geological structure of the basin and controls the paleo-tectonic pattern of the basin.Therefore,it is not only the key entry point to study the paleo-tectonic recovery of the whole Tabei uplift by clarifying its fault system and genesis mechanism,but also the primary task of deepening understanding the paleo-tectonic pattern of Tabei uplift and its relationship with oil and gas.Based on the previous studies,this paper studies the strata structure and fault system of the Tabei uplift axis,and makes use of the latest 2D/3D seismic data and drilling data to establish the age stratigraphic framework of the study area and analyzes its geological structure;According to the fault-related fold theory,the fault geometry and kinematic characteristics are analyzed in detail,and the fault system is established at different periods.According to the principle of equilibrium restoration,the mechanism of fault formation is discussed.The following conclusions are obtained in this paper:(1)There are seven unconformities in the study area: Z/AnZ(Td)?S/AnS(Tg5)?T/AnT(Tg)?J/AnJ(T8-3)?K/AnK(T8-2)?E/AnE(T8)?Q/AnQ(T3).From the bottom up can be divided into five tectonic-stratigraphi sequence,including the base structure sequence,the Lower Paleozoic tectonic sequence,the Upper Paleozoic tectonic sequence,Mesozoic tectonic sequence and the Cenozoic tectonic sequence.(2)The fault system on the flat surface in the axis of the Tabei uplift is approximately trending NEE or EW,which has not only developed a large-scale of compressional fault,but also developed many small transtensional faults in the extensional structures.The reverse faults are mainly found in the Mesoproterozoic,Paleozoic;The normal faults are focused in the Mesozoic and Cenozoic strata above the pre-existing reverse faults.The main faults are mostly inclined to the axis of the uplift,and they are mostly in the form of back thrust structural styles,and the faultplanes are more gentle in upper part and steep in lower part.It has early developmental stages,long evolution period,large scale,and display characteristics of inheritance and superposition.(3)The evolution of the regional equilibrium profile in the Tabei uplift shows that the uplift mainly experienced the embryonic period,the qualitative stage,the reconstruction period and the decay period,formed the present tectonic pattern.The thrust faults are mainly developed in the early Ordovician,the basic shape of the late Permian,the transtensional faults are mainly formed in Paleogene and Neogene,and the most intense activity in the early Neogene.(4)The opening and closing of the oceanic crust is the main source and mechanism of the development of the basin and the fault,and the fault activity is the main factor of the formation and transformation of the uplift.The fault activity controls the tectonic evolution of the uplift and the regional tectonic pattern.The development of secondary faults restricts the distribution and tectonic pattern of secondary zones.(5)The presence of detachment layers in the region affects the formation and distribution of faults.Yanan fault and Shaya-Luntai fault along the basement detachment surface to form fault propagation fold pattern.Flexural deformation and sedimentary-tectonic load of lithosphere is the main mechanism of Meso-Cenozoic normal fault development.The orogenic effect of the Tianshan fold belt and the compressive stress applied to the basin are one of the dynamic mechanisms that induce this deflection.