Abstract:

As the NW-trending dextral strike-slip fault on the northern margin of the Tarim Basin, the Kalayu’ergun Fault defines the western boundary between the western Kuqa Depression and Wensu Bulge. It holds immense importance to understand the deformation occurring within the Kuqa Depression. However, there is still ongoing debate regarding the length, activity time and formation mechanism of the Kalayu’ergun Fault. In this study, a comprehensive investigation was conducted, incorporating sub-surface geophysical data, high-resolution remote sensing satellite images, and the findings of previous researchers. The results demonstrate that the Kalayu’ergun Fault cuts off the Awate anticline in the north, and to the south, it extends near the southern flank of the North Kalayu’ergun anticline but does not reach the Middle Kalayu’ergun anticline. The total extension of the fault is estimated to be approximately 40km. And the minimum of the fault strike-slip distance is estimated by the sum of the tectonic shortening of the North Kalayu’ergun anticline and the shortening absorbed by the strata on the northern flank of the Awate anticline through drag, which amounts to about 4.1-4.3km. Additionally, the Kalayu’ergun Fault has been active since its formation in the early Pliocene, but its activity intensity has been weakened obviously. The activity of the Kalayu’ergun Fault corresponds to the deformation time of the North Kalayu’ergun anticline, which is consistent with the deformation time determined using the same structural sedimentary constraints. This indicates that the North Kalayu’ergun anticline was formed under the combined action of near north-south compressional and horizontal shear stresses. The development of this transverse fault is synchronous with the overthrust structures on both sides and is developed in synchrony with the strong uplift of the southern Tian Shan orogenic belt since the late Cenozoic. The formation of the Kalayu’ergun Fault can be affected not only by the differences in the basement nature on both sides but also closely related to the difference in the thickness of the gypsum salt layer. The former resulted in variations in horizontal shortening on both sides of the fault, leading to the tearing of the Cenozoic sedimentary cover. The latter, which under the action of the extrusion stress, influenced the generation and evolution of salt-overlying beds, and then influenced the formation of the fault. In addition, the existence of prior salt structures, also known as salt diapirs, may have also played an important role in the formation of the fault. As the boundary fault in the western part of the Kuqa Depression, the Kalayu’ergun Fault is responsible for accommodating crustal shortening on both sides and even in the whole eastern and western parts of the Kuqa Depression. As a result, the shortening of the Kuqa Depression gradually decreased from east to west. Furthermore, the Kalayu’ergun Fault also had significant impacts on geomorphology, as it controls and modifies the landscape in the southern Tian Shan foreland basin. In the meanwhile, the Kalayu’ergun Fault creates favorable conditions for the transportation and accumulation of oil and gas resources.

Key words: Kalayu’ergun Fault, Kuqa Depression, dextral strike-slip fault, formation mechanism

摘要：

喀拉玉尔滚断裂是塔里木盆地北缘、 库车坳陷西边界的一条NW向右行走滑断裂, 同时也是库车坳陷和温宿凸起的分界断裂, 对其开展研究对于认识库车坳陷的构造变形具有重要意义, 但目前对该断裂的展布特征、 活动时间及形成机制仍存在较大争议。文中根据深部地球物理资料、 高分辨率遥感卫星影像解译, 并结合前人研究成果, 对该断裂进行了系统的研究工作。结果表明, 喀拉玉尔滚右行走滑断裂向N延伸穿过了阿瓦特背斜, 但其S向并未延伸至北喀背斜南部, 总体延伸约40km, 走滑断距约达4.1~4.3km。喀拉玉尔滚右行走滑断裂形成于上新世初期, 其活动可能一直持续至今, 但强度已明显减弱。喀拉玉尔滚断裂的形成除了受断裂两侧基底性质差异的控制外, 还与膏盐层的厚度差异密切相关。前者影响了断裂两侧地壳水平缩短量的差异, 从而导致新生代沉积盖层被撕裂; 后者在挤压应力的作用下影响盐上构造层的产生与演化, 进而影响断裂的形成。此外, 先期盐构造(盐底辟)的存在可能也对断裂的形成起到了重要作用。喀拉玉尔滚右行走滑断裂作为库车坳陷西部的边界断裂, 对其两侧甚至整个库车坳陷东、 西部地壳缩短量有一定的调节作用。同时, 断裂对南天山前陆盆地的地质地貌、 油气资源的运移与聚集也产生了显著影响。

关键词: 喀拉玉尔滚断裂, 库车坳陷, 右行走滑断裂, 形成机制