| The Bachu uplift is a composite paleo-uplift with multi-stage kinematic evolution, and its deformation process is strongly controlled by the combination of the western Kunlun Mountain, the southern Tianshan Mountain and the Altyn orogen. The characteristics of the Bachu uplift and its structural histories would provide support evidence to understand the evolutionary of the surrounding orogens. Specifically, the Bachu uplift was a mutual fore-bulge of both the northern and southwestern Tarim Basin in mid-late Paleogene, and the unconformities preserved within the uplift would unravel the fore-bulge migration process.Based on the interpretations of high-resolution seismic data and well logging, in combination with tectonic evolution sections and Sedimentary thickness analysis, the structural styles and superimposed transfor-mation process of Bachu uplift are researched, moreover paleo-uplift migration and dynamic mechanics are analyzed. Following conclusions can be made by the research of this dissertation.1. Based on the fault geometry, structural styles of the study area are proposed. The structural styles of Bachu uplift include extension, compression, strike-slip and inversion, forming complex combination types through superimposing and transforming. Among them, the style of the boundary faults is mainly trishear thrust structure, showing "y" and anti-"y" glyphs structure characteristics on the profile, because of combining strike-slip property. Shallow detachment fault developed in the south boundary, becoming a vertical superposition structure style with the lower basement-involved fault. Intra main faults show the multi-periodic activity features, which is early normal fault reversal or early thrust fault transformed by the late transformational fault. And the internal secondary faults show positive (east uplift) and negative (hanging wall of the boundary faults) flower structure styles, controlled by different period stress.2. According to the strike and period of fault belt, the dynamic properties of fault systems are determined. The early Caledonian extension fault system, the middle Caledonian compression fault system, the late Hercynian extension fault system and the Himalayan transpression fault system are recognized, and the late Caledonian-early Hercynian strike-slip fault system is put forwarded for the first time. Contacting with the peripheral orogenic belt evolution, this paper indicate that, the early Caledonian extension fault system and the middle Caledonian compression fault system are controlled by the opening and closing of the ancient Kunlun ocean, the late Caledonian-early Hercynian strike-slip fault system is mainly related with the collision of ancient Altyn, the late Hercynian extension fault system is greatly influenced by the south Tianshan orogen, and the Himalayan transpression fault system is controlled by both the south Tianshan orogen and west Kunlun orogen.3. The Bachu uplift is a composite paleo-uplift with multi-stage kinematic evolution, and its deformation process can be divided into four periods:(1) Caledonian-early Hercynian, with the opening, subduction and closing of the ancient Kunlun and ancient Altyn oceans, the Bachu uplift is in the depression-uplift alternating development stage. (2) Middle-late Hercynian, the collision of the south Tianshan orogeny leads to local uplifting of the western Bachu uplift. However, the eastern Bachu area is also a depression because of the uplifting of the Hetian paleo-uplift, and the eastern Bachu area is still in a high southern and low northern tectonic framework. (3) Indosinian-Yanshanian, influenced by the micro continental collision of the Tibet Plateau, the study area is in the overall uplift stage. Bachu, Keping and south-western Tarim are in a unity uplift at this time, and the Bachu region is in tectonic framework of high in the West and low in the East. (4) Himalayan, effected by the remote control of the Indo-Tibet collision, the south and north boundary faults intensely act. Tectonic load and intraplate stress lead to lithospheric flexure. The Bachu Uplift rapidly uplifts and goes into fore-bluge evolution period.4. Combining fault system and tectonic evolution, the important control action of fault activity to uplift evolution and enlightenment of uplift form to fault activity time are pointed out. The controlling of fault activity to uplift evolution can be divided into three stage: Middle Caledonian compression fault system controls the low uplift of eastern Bachu area. Early Himalayan the Aqia Fault and western Tumuxiuke fault act, controlling the distribution range of Paleogene northern paleo-uplift. Middle Himalayan the south and north boundary faults intensely thrust, and fault activity totally controls the uplift location. On the other hand, due to the consistency of uplift deforming and fault activity, uplift form has a great enlightenment to fault activity time in the area of lackingstratigraphic.5. Based on the Cenozoic uplift mechanism and orogen evolution, fore-bluge evolutionmodel of Cenozoic forland basin system in the Tarim Basin and the fore-bluge migration model are built. The evolution of for-bluge is mainly divided into three periods:Early Himalayan fore-bluge founding period, middle Himalayan fore-bluge developing period and late Himalayan fore-bluge buring period. Middle and late Paleogene the west Kunlun orogeny has already started to uplift, and south-western and northern Tarim foreland basins began to form. The Bachu uplift become the common fore-bluge of the foreland basins. Miocene the remote control of the Indo-Tibet collision leads to strong intraplate stress, and the Bachu Uplift intensely uplifts and exhumates because of the weak basement strength. Pliocene, the west Kunlun and south Tianshan orogeny have entered into the rapid uplift phase, fast erosion and sediment transport lead the Bachu fore-bluge to accept deposits, and sedimentary load aggravates the Bachu fore-bluge’s subsidence and burial. In the whole Cenozoic evolution, the Bachu fore-bluge shows a stepped migration from the south to the north, reflecting the west Kunlun orogen continuously advancing to the craton direction. But because of long-term activity of the north boundary faults, migration of the north fore-bluge is stagnant, and replaced by the vertical development, which promotes the formation of a high amplitude fore-bluge. |
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