Main features and structural evolution of southern boundary fractural zone of the Bachu fault-rise in western Tarim Basin

The Bachu fault-rise is a sub-order tectonic unit of the Tarim Basin, and its southern boundary, created since Late Mesozoic, is a complicated fractural zone. Based on a brief introduction to each fault, this paper synthetically described main geometric and kinematic characteristics of the southern boundary fractural zone. The fractural zone experienced three major thrusting events, which occurred in Cretaceous, Miocene (-Pliocene) and Pleistocene (-Holocene) respectively. The Cretaceous thrusting was developed only along the southern boundary, and the northern boundary, such as the Tumxuk fracture, acted as a boundary between the Bachu fault-rise and the Awati sag in Jurassic-Cretaceous, instead of thrusting. The Cenozoic thrusting events synchronously occurred along both the southern and northern boundary fractural zones of the Bachu fault-rise. An analysis of basin-orogenesis coupling reveals that the northward thrusting in Cretaceous and Pleistocene (-Holocene) should have been related to northward expansion of the foreland fold-and-thrust belt of West Kunlun, while the south(west)ward thrusting in Miocene (-Pliocene) might have been coupled with southward expansion of the South Tianshan fold-and-thrust belt. All of the three generations of thrusting were accompanied by the shearing fractures, which made up a transfer zone in the thrusting system. The Cretaceous NW-trending dextral strike-slipping fractures played an important role in the segmentation and complication of the southern boundary fractural zone of the Bachu fault-rise.