关键词: 喀拉玉尔滚断裂, 库车坳陷, 右行走滑断裂, 形成机制

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