Abstract:

Using the regional geological, seismic, and well data, this paper investigates the Mesozoic basin structure and tectonic style,
Mesozoic original thickness of strata and depositional system, paleo-uplift topography, and regional tectonic evolution in Kuqa
depression. Subsequently the paleogeography of the Mesozoic basin is reconstructed and factors of basin prototypes in Kuqa depression are analyzed. The residual Mesozoic strata in Kuqa depression show that the geological structure becomes thinner from the north to the south, and is stripped in the north and overlapped in the south. The northern part is marked by a large angular unconformity on Hercynian fold belt of south Tianshan, and the southern part shows a gentle angular unconformity on Cambrian or Ordovician. The basement faults have movements along with the WenSu-XiQiu-YaHa palaeohighs in the southern edge. The alluvial fan and braided river delta were developed in the northern monoclinal belt, and the deep-lake facies was developed in Crassus structural belt. Along with the southern palaeohighs were the gentle slope delta and a shallow lake. The Mesozoic prototype basin of Kuqa depression belongs to the transitional zone of Hercynian orogenic belt in southern Tianshan and the Tarim craton. The isostasy may be the main factor on the passive margin of the subsidence of Mesozoic basin. During the expansion of the Southern Tianshan Ocean, the southern palaeohighs were on the passive margin of Tarim cratonic platform. When the southern Tianshan ocean closed, the southern palaeohighswerelocatedonaupliftedbeltoftheforeland.Basementfaultsweredevelopedwithfaultblockshavingdifferentmovementsand
the southern palaeohighs were inherited in the Mesozoic. In the late Cenozoic, the southern palaeohighs experienced compressional deformationassociated with the up lift of new Tianshan,and then became the frontal thrust deformation of orogenicwedge in the new Tianshan.

Key words: Tarim Basin, Kuqa depression, tectonic paleogeography, prototype basin