西昆仑－塔里木盆地盆－山结合带的中、新生代变形构造及其动力学

The basin-range junction belt on the southern margin of the west Kunlun-Tarim basin can be divided into the northern West Kunlun belt and the southern Tarim depression belt. The latter consists of the southwestern Tarim depression and the southeastern Tarim fault depression. The northern West Kunlun belt is separated from the central West Kunlun belt and southern Tarim depression belt by the Kuda-Kaxtax fault and by the northern West Kunlun thrust, respectively. The formation and evolution of the basin-range tectonics progressed through a lengthy and repeated process, but the types of deformation structures formed at different times and at different levels show much consistency. This process was generally manifested as follows: with the central West Kunlun fault (whose main part is the Kuda-Kaxtax fault) as the root zone, the basin-range tectonics mainly experienced north-vergent thrust faulting towards the interior of the southern Tarim depression belt This north vergent thrusting was gradually transformed to mainly vertical tectonic extension. Thrusts in the southern Tarim depression belt and those in the northern West Kunlun belt are components at different tectonic levels in a unified geodynamic system; the former (brittle faults) were the product of propagation of the latter (ductile faults) toward shallow-level, brittle strain domains. The driving force for the formation of the basin-range tectonics was the continuous, strong north-verging thrust propagation coming from the south of the Kunlun tectonic belt. At present, no direct evidence of south-verging subduction of the Tarim block has been found, at least in areas of pre-early Pleistocene strata in the southern Tarim depression belt The basin- and mountain-forming processes on the West Kunlun, the southern margin of Tarim basin simply comprise three stages: late Jurassic-early Cretaceous relatively strong and differential uplift and subsidence; late Cretaceous-Paleogene isostatic and slow uplift and subsidence; and Neogene-present strong and rapid uplift and subsidence. Basin-range tectonics of the Miocene-Pliocene were major transition periods for the basin- and mountain-forming mechanisms. Terminal early Pleistocene tectonic movements laid a foundation for the basin-and-range tectonic framework on the West Kunlun, the southern margin of Tarim basin.