Research On Uplift-Depression Framework Evolution And Its Tectonic Control Mechanism In The Central Uplift Belt, Tarim Basin

This work was started with the detailed analysis of the faults systems of Central Uplift Belt in the Tarim Basin. Based on the accurate geological structure interpretation of the seismic profiles, with comprehensive application the recovering of denudation thickness, making tectonic evolution profiles, subdidence history analysis and uplift-depression tectonic framework analysis, and so on, this paper has determined the controlling actions of the fault systems in the evolution of the Central Uplift Belt, the transition of uplift-depression tectonic framework, and the evolution of Tarim marine craton basin. The main achievements of this paper are followes:1. Determined the classification system of the structure deforming styles in the Central Uplift Belt of Tarim BasinThe geometry characters of the main fault belts and the related folds were detailed described and analyzed by the accurate interpretation of the seismic data. There are abundant different deforming styles, among of these the compressional structure style is the most significant one. Accoding to the degree of basement involved, the compressional structures can ben classified to basement-involved type and cover-decollement type. The latter style mainlydeveloped at the palce where gypsum mudstone existed; while the basement-involved structures widely developed in the higher position of the basement uplift.According to deforming mechanism, the extensional structures, strike-slip structures and compressional structures developed in the study area, but the compression structure type is the main one. Considered the tectonic evolution of these structures zone, the earlier extensional and compressional structures reversed and formed different structure styles at the later deforming periods. Based on the above integrated analysis, the classification system of the structure deforming styles in the Central Uplift Belt of Tarim Basin has been determined and the faults structure styles can be divided into four major types which are the compressional structure, the extensional structure, strike-slip structure and the inverse structure. Then these four structure styles can be divided into 20 complex sub-types. Superimposed reformation of different styles structures can formed more complex structural combination types.2. Based on the periodization and system matching analysis of faults in Central Uplift Belt, this paper determined the active stages and forming epochs.The Central Uplift Belt developed several stages of fault system during its long evolutionary process, Through the detailed seismic profile interpretation and multidisciplinary analysis the interrelationship of faults,unconformity interface and growth strata, we classified the fault system of the Central Uplift Belt to three large phase fault syetems:middle Caledonian Orogenyâ… episode(end of Early Ordovician) fault-syetem, middle Caledonian Orogenyâ…¡episode(end of Late Ordovician) fault-syetem, and middle-late Himalayan (since late Miocene) fault-syetem.(1) The middle Caledonian Orogenyâ… episode fault-syetem chiefly distributes in the Tazhong Uplift, which be consisted by Tazhong 1 Faut, Tazhong 22 Faut, Tazhong 2 Faut, Tazhong 10 Faut and TuMxk-BaDong deep Fault.These faults strike NW, constringe eastward, disperse westwad, and form a "brush structure" shape in plane.The Tazhong 1 Faut, which is the northern boundary fault of Tazhong uplift, is the most important fault. In the western it back thrusted with the southern Tazhong 22 fault, which formed a "pop up structure". The fault's palne became gentler in the eastern segment of Tazhongâ… Fault, and a fault-bend fold was developed in its hanging wall, insteading of a "pop up structure".(2) The middle Caledonian Orogenyâ… episode fault-syetem chiefly distributes in the south Tazhong uplift,TangGubasi depression and southern TaDong uplift, forming a series of northeast strike fault system. CheErcheng fault started thrusting intensely and showed appeared some slip character in this period. The middle Caledonian Orogenyâ… episode fault-syetem in the Tazhong uplift inherited acting and caused the further uplift. The MaDong-Tabei fault, Tazhong 8 well fault, Zhong 3 well fault, Tazhong 5 fault, TangGubasi 1 fault and TangGubasi imbricate faults started thrusting intensely, forming a arcuate zone protrudes to the northwest. And the TangGubasi 1 fault, Zhong 3 well fault, and Tazhong 5 fault acted as the front faults and overlayed on the previous fault system. The previous different structure styles cased the later superimposed reformation action heterogeneity in different tectonic areas. In the west, the front faults (TangGubasi 1 fault, Zhong 3 well fault) facing thrust with a series of ramp faults, such as Tabei fault,Tazhong 8 well fault, forming a "thrust-triangle-zone". In the east, the front faults (Tazhong 5 fault),acting as a single thrust fault, overlaying above the hanging wall of Tazhong 1 fault that formed previously. The scale of reverse faults developing in TaDong uplift was limited, mainly behaving as the CheErcheng fault started thrusting.(3) The middle-late Himalayan (since late Miocene) fault-syetem mainly distributed in the Bachu uplift which lies in the western section of the central uplift. Fault strike changing from NWW to NW in the western section of Bachu uplift. The attitudes of faults which controlled the formation of the Bachu fault-uplift are generally steep dip and display compresso-shearing character. The thrust Selikbuya-Mazhatage fault system which slip along the Paleogene decollement horizon developed in the southern edge of Bachu uplift. The fault system can be tracked to the southwest Kunlun Mountains Preshoot belt, and could be connected to Kasa faults belt in the westward, and act as front fault belt of current Ta Southwest foreland thrust system.Base on the above analysis, according to faults combination style, the front belt of the fault system in the central uplift belt can be divided into three kind:â‘ Back-thrust style which composed by the faults thrust to opposite direction;â‘¡Facing-thrust style which composed by the front belt and its ramp faults. This kind of faults combination is mainly developed in the southern margin of Tazhong uplift, which is make up of TangGubasi thrust front fault zone (TangGubasi 1 fault, Zhong 3 well fault) and its ramp fault zone (MaDong-TangBei fault,Tazhong 8 wells fault), and a "thrust-triangle-zone" was developed. This type of combination also be found in the southern edge of Bachu uplift. SeLibuya-Mazhatage shallow fault zone and inherited active KangTakumu fault zone, SeLibuya faults combined as recoil structure;â‘¢Single thrust-type which is quite simple, and is make up of a single thrust fault and its fault-propagation fold. This type of fault system is mainly developed in the east part of Tazhong uplift (Tazhong 5 faults) and the southern margin of the Bachu uplift (SeLibuya-Mazhatage shallow fault).3. The evolution process of the central uplift belt was analyzed, and the controlment of faults was prominent in the development process of the uplift. This paper built a development model of central uplift belt controlled by fault.Based on the recovery of denudation thickness of main unconformities by geological extrapolation method, we compiled 6 tectonic evolution sections across the uplifts tectonic units, analyzing the tectonic evolution process. The result shows that the central uplift belt was actually a composite uplift, comprised of many uplifts, each of which had different structural styles and experienced complex tectonic evolution processes. Bachu uplift experienced back-bulge ramp in the mid-late of Caledonian period,forebulge in the Hercynian-Yanshanian period and the latest compressional fault uplift in the mid-late of Himalayan period; Tazhong uplift started at the first episode of Caledonian period and formed at the second episode of Caledonian period; Tadong uplift started and formed at the second episode of Caledonian period.Combined with the tectonic evolution analysis of the fault systems, it showed that the development and evolution of the fault systems significantly controlled the formation,reconstruction and setting of the uplift. The controlment appeared as follows:(1)The activity of the faults controlled the structural style of the uplift. The combination types of the fault system in the central uplift belt were abundance, which resulted in the diversity of uplift types. This paper divided the bulge structures styles of the central uplift belt into back thrust,fault-bend fold and extrusion:â‘ back thrust typed ancient uplift is formed by the back thrust of thrust faults on both sides and the uplift upheaves in the form of fault blocks. The Bachu uplift and the Tazhong uplift all belong to this type;â‘¡fault-bend fold ancient uplift goes with the hanging wall of low angular ramp-flat thrust faults and is controlled by the fault-bend anticline fold. This type developed in the Eastern of Tazhong uplift, formed by the fault belt I and thrusted by the fault belt 5;â‘¢extrusion ancient uplift is defined newly in this paper. It is controlled by the anticline formed by the side extrusion. The difference from the former two types is that it lied on the footwall of the main fault. So is the Tadong uplift.(2)The activity of fault system reconstructed the uplift. Almost all of the bulges in the Tazhong uplift experienced the reconstruction. Besides some extent reactivation of the former faults, the central uplift belt experienced many other types of reconstruction. This paper divided the types of reconstruction into composite back thrust type,folded type and superposing thrust type:â‘ the composite back thrust type is mainly developed within the former back thrust bulge and raised more insice the uplift. Bachu uplift belongs to this type. Generally speaking, the back thrust of the former faults control the formation and configuration of the uplift, for example, the Serikbuya-Mazartag fault and Tumuxiuke fault; later the sub-level faults thrusting control the formation of the tectonic units within the uplift;â‘¡the folded type is referred to that uplift was raised by the form of fold when the fault which controlled the formation of the uplift weaken. This type mainly developed in the western of Tazhong uplift. At the end of Early Ordovician, the Tazhong fault I and 22 controlled the formation of fault block; At the end of Late Ordovician, the thrust faults activated intensely in the south of uplift and the ramp tectonic formed. By the intense impression stress, the Tazhong uplift was raised on the form of fold deformation. In the seismic profile, the strata were onlap and thin out and truncation at the top of the uplift.â‘¢superposing thrust type usually developed in the uplift which was broad and wide in the early stage and superposed by the thrust faults along the gentle limb. In the studying area, this type was mainly developed at the east segment of Tadong uplift. At the end of Early Ordovician, the Tazhong fault I began to activiate and the fault-bend fold ancient uplift developed on the hanging wall; At the end of Late Ordovician, the Tazhong fault 5 thrust along the wing of the fold and the fault propagation fold developed on the hanging wall, which superposed on the former fault bend fold. So the dual-style fold uplift formed. At the south margin of Bachu uplift, Serikbuya-Mazartag shallow fault belt which reconstructed the uplift belongs to this type.(3) Fault activity controlled the tectonic attributions evolvement of upliftsDevelopment of the current uplift of the Tarim Basin are basically controlled by the fault block uplift, However, during the uplift of the tectonic evolution, uplift of the formation and rupture when the development does not isochronal. This paper took Bachu uplift as anexample, combining with basin tectono-Sedimentary Analysis, proposed that all the uplifts in the Central Uplif Belt of Tarim Basin have experienced from the Foreland uplift to Faulting uplift.â‘ Foreland uplift phases:uplift based on deformation of flex, non-developmental thrust fault and elevated to a lesser extent, the top subject to a certain degree of erosion. Foredeep is controled by deflection sedimentation,which is located between uplift and orogenic belt fold thrust zone then formation onlap fill toward forebulge in the foredeep.â‘¡faulted uplift phases:With the front of orogenic belt pushed to intracraton incessantly, Foreland basin system's foredeep and forebulge gradually be drawn into strong lateral extrusion. Foredeep area through extrusion further subsidence, the property of depression by the early foredeep translate syncline-type subsidence, and the forebulge go through compression which behaved fault block move upward, so it suffer the strong erosion. The development of thrust fault is a significant geological signs which divided into uplift zone from forebulge to faulted uplift.4. Systematic analyze the change of the uplift-depression framework and the faults controlling action in the Tarim BasinBased on the subsidence history rebuilt, we completed the compared process figures and the evolution maps of the main uplift-depression units about the different deformation periods. Combined the regional tectonic evolution profiles, the end of the early Ordovician, the end of the late Ordovician and the middle and the end of the Sishan Movement are the main deforming periods of the uplift-depression framework of the Tarim Basin.During the episodeâ… of the middle Caledonian Orogeny at the end of the early Ordovician, the Tazhongâ… and 22 fault belts started to acting, and caused the origin of the Tazhong uplift and the ancient uplift at the front of the Taxinan Mountain, also probably the ancient Tabei uplift, and involved the deeply subsidence of the Tagubasi. Meanwhile, the Awati district became the relative shallow bottomland and connect the Manjiaer depression, formed the deep trench sediments. They separated the Tabei uplift and the Tazhong-Taxinan uplift which also separated the Awati and Tanggubasi depression. At the east, the Manjiaer depression related the Tanggubasi depression. Therefore, the uplift-depression interphase framework formed in the Tarim basin. During the episodeâ…¡of the middle Caledonian Orogeny at the end of the late Ordovician, the faults at the southeastern Tarim basin began to act intensively. The Tazhong and the Taxinan uplift continued to rise, the Tabei district began to rise and the Tadong uplift start to form, and the Tanggubasi depression was destroyed and became the uplift. The area of the Manjiaer depression became smaller because of the compression from both sides. The subsidence center migrated north and connected the Awati depression as a huge striking EW depression. Therefore, the tectonic framework of the Tarim basin appeared that the two striking NS uplift located one depression between them. Then, the uplift-depression framework of the eastern Tarim basin was finalized. Though the basin was reformed during many different tectonic periods, the tectonic framework was stable. At the middle and end of the Himalayan Movement, the thrust faults acted strongly, the Bachu block uplift raise rapidly and the Taxinan and Awati depression at the both sides subsided rapidly. Finally, the uplift-depression framework was more obviously and stable. Combined the above analysis, the deforming evolution of the three faults systems of Central Uplift Belt in the Tarim basin was the important control factor to the transation of the uplift-depression framework in the Tarim basin.5. Based on analyzing the process of the formation, disintegration and extinction of Tarim marine cratonic basin, this paper puts forward two kinds of marine cratonic basin evolution model about eastern and western Tarim Basin,and points out the role of central uplift belt in the process of basin evolution.Take the analysis of fault system formation and evolution in the central uplift belt and its impact on the pattern of uplift-and-depression framework changes as an cut-in point, integrated sedimentary paleogeography of the Tarim Basin which predecessors researched, divided evolution of marine cratonic basin into three periods which are formation, disintegration and extinction.Analysis showed that the fault system of Caledonian I screen opened the development process of the disintegration of the marine basin, which directly controls the formation of Tazhong uplift, and divides the unified extentional cratonic marginal depression basins and intracratonic depression basin into three different characteristic depression basin; The fault system of Caledonianâ…¡screen not only causes a large-scale uplift in eastern part,but also makes a sharp contraction of the north of Manjaer depression, and from then on although experienced sea intrusion, but the whole eastern is in the uplift condition, entereing to the extinction evolution period. The Western disintegration process was beginning with the formation of Southwest palaeohigh and Buchu foreland uplift which wasn't effected by fault controlling, and was in the depression background and developed marine deposit because of the uplift of eastern,it has no significant effect in the disintegration of the marine basin. Therefore the formation of the two periods of Caledonian fault system is the most important reason of disintegration of the Tarim craton marine Basin.6. Discussed the formation mechanism of the fault system in the central uplift belt, ascertained the dynamics properties of every fault system, and divided the dynamical districts of the fault system.Integrated a large number of previous research results indicate that the Precambrian basement was formed by the collage of the southern and northern Tarim plate during the Neoproterozoic era. During the process of the collage, there was a nearly striking NS intracontinental orogeny belts at the central uplift area in the Tarim Basin. Meanwhile, the island-arc collision orogenic belt (the central orogenic belt) existed at the south of the Tarim basin, which extended NE. The weak basement caused by the plates'collage was one of the important factors to control the multi-phase development of the large-scale fault system in the central uplift area.Meanwhile, based on the comprehensive analysis of the geometry, kinematics and dynamics characteristics of the basin fault system, we compared the most significant kinematical events of the surrounding orogenic belts with the deformation of the fault systems in the Talimu basin at different stages, combined the previous research of the movement of the palates surrounded the Talimu basin. The results indicated three important events. First, the formation of the fault systems during the episodeâ… of the middle Caledon movement was related with the initial collision and the intensive subduction of the ancient Kunlun Ocean during the end of the early Ordovician to the beginning of the middle and late Ordovician. Second, the formation of the fault systems during the episodeâ…¡of the middle Caledon movement was related with the onset of the subduction of the northeastern branch of the ancient Altun ocean at the early and middle Ordovician and the close and the collided northwestward with the Talimu plate. Third, the fault systems'formation during the middle and late Himalayan movement was the tectonic response to the intensive subducation between the Indian-Eroasia plate and the thrust of the western Kunlun Mountain. These three tectonic events is not close to the evolution of the southern Tianshan. Therefore, the three faults systems can be considered as two important dynamical districts which are related to the western Kunlun orogenic belt, and the Altun orogenic belt. This mean that the primary dynamical relationship was built between the evolution of the basin marginal orogen and the formation of the intrabasin fault systems.