摘要:造山带和盆地是在时空发展和形成机制上具有密切联系的构造系统。青藏高原内部晚三叠世古特提斯造山带的形成，对北缘的塔里木盆地产生了重要的影响，导致了盆地内部西昆仑山前地区发生了强烈的冲断构造变形，而这一冲断构造变形所形成的古构造—古地貌对后期侏罗—白垩纪的沉积具有重要的控制作用，同时也决定了该地区的油气分布。本文基于对西昆仑山前露头区中生代地层分布详细的野外考察和盆地覆盖区钻井资料的整理，结合对盆—山结合带清晰地震剖面的详细解释，开展西昆仑山前的晚三叠世古构造特征及侏罗—白垩纪沉积充填过程研究，以期揭示晚三叠世的古构造—古地貌特征及对沉积的控制作用。通过研究发现，西昆仑山前地区发育晚三叠世前陆褶皱冲断带，冲断带根部发育基底卷入构造，锋带发育叠瓦状构造；古生界受逆冲断裂控制，形成一系列的北陡南缓的背斜隆起，冲断带前锋位置与新生代构造前锋位置相近。三叠纪末古地貌形态由于特提斯造山带的强烈隆升，总体呈南高北低的地貌形态，但是褶皱冲断构造带受地表风化剥蚀作用，背斜核部形成南缓北陡的古隆起，而断层破碎带形成南陡北缓的洼地，是侏罗系发育前的基本地貌格架。早侏罗世受特提斯造山带造山后伸展的影响，西昆仑山前发育4个箕状断陷，控陷断层发育于古造山带一侧；受大型控陷断层的影响，在断陷内部呈北高南低的地形特点，断陷内侏罗系逐渐向北部斜坡超覆。晚三叠世形成的古构造—古地貌与早侏罗世断陷叠加形成的古地理格架一直控制了侏罗纪—早白垩世的沉积，直到晚白垩世沉积时才没有起到控制作用。?
关键词: 构造/
古地貌/
沉积作用/
晚三叠世/
侏罗—白垩纪/
西昆仑山前
Abstract:Basin and range are the uniform tectonic system which are closely linked in temporal and spatial development and formation mechanisms. Formation of the Late Triassic Paleo-Tethys orogenic belt in the Tibetan Plateau had a significant impact on the southern margin of the Tarim Basin. This orogenic event caused an intense thrust deformation in the front region of western Kunlun Mountains. The paleo-geomorphy formed by this thrust deformation had played an important role in controlling the Late Jurassic-Cretaceous deposition. Meanwhile, it also determined the distribution of oil and gas in this area. Based on a detailed field survey of Mesozoic strata in the outcrops of the western Kunlun Mountains, and combined with the analysis of drilling data and the detailed interpretation of high quality seismic profiles, this paper studies the characteristics of Late Triassic paleo-structure and the sedimentary filling process of Jurassic-Cretaceous in the piedmont of western Kunlun Mountains, in order to reveal the Late Triassic paleo-structure and its control of deposition. A Late Triassic foreland fold and thrust belt is found in front region of western Kunlun Mountains where basement involvement structure developed in the root and imbricated structure developed in the front zone respectively, and the position of frontier fault of the Triassic foreland fold and thrust belt is near the frontier fault of Cenozoic fold and thrust belt. Controlled by these thrust faults, the Paleozoic strata formed a series of anticline uplifts with steep north rim and gentle south rim. Triassic paleo-geomorphy showed lower from south to north in general due to the intense uplift of the Tethys orogenic belt. Affected by surface weathering and erosion, the paleo-uplifts in the core of anticline had the shape with steep north slope and gentle south slope, but the depressions related to the fracture zone usually had the shape with gentle north slope and steep south slope, and such paleo-geomorphy feature is the basic geomorphological framework before the deposition of Jurassic sequence. During the Early Jurassic, four half graben rifts developed in the piedmont of western Kunlun Mountains due to post-orogeny rifting extension where the basin controlling fault developed on the side of Tethys orogenic belt. Interior of rift depression, the paleo-geomorphy was higher from south to north, and the Jurassic sequence was onlap deposition to the north slope. The paleo-geographical framework which was the superimposition composed of paleo-geomorphy caused by the Late Triassic deformation and the Early Jurassic rifts controlled the deposition of Jurassic-Early Cretaceous, until Late Cretaceous.?
Key words:Paleo-structure/
Paleo-geomorphy/
Deposition/
Late Triassic/
Jurassic to Cretaceous/
Piedmont of western Kunlun Mountains
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