Basin‐ and Mountain‐Building Dynamic Model of “Ramping‐Detachment‐Compression” in the West Kunlun‐Southern Tarim Basin Margin

Abstract: Analysis of the deformation structures in the West Kunlun‐Tarim basin‐range junction belt indicates that sediments in the southwestern Tarim depression were mainly derived from the West Kunlun Mountains and that with time the region of sedimentation extended progressively toward the north. Three north‐underthrusting (subducting), steep‐dipping, high‐velocity zones (bodies) are recognized at depths, which correspond to the central West Kunlun junction belt (bounded by the Küda‐Kaxtax fault on the north and Bulungkol‐Kangxiwar fault on the south), Quanshuigou fault belt (whose eastward extension is the Jinshajiang fault belt) and Bangong Co‐Nujiang fault belt. The geodynamic process of the basin‐range junction belt generally proceeded as follows: centering around the magma source region (which largely corresponds with the Karatag terrane at the surface), the deep‐seated material flowed and extended from below upward and to all sides, resulting in strong deformation (mainly extension) in the overlying lithosphere and even the upper mantle, appearance of extensional stress perpendicular to the strike of the orogenic belt in the thermal uplift region or at the top of the mantle diapir and localized thickening of the sedimentary cover (thermal subsidence in the upper crust). Three stages of the basin‐ and mountain‐forming processes in the West Kunlun‐southern Tarim basin margin may be summarized: (1) the stage of Late Jurassic‐Early Cretaceous ramping‐rapid uplift and rapid subsidence, when north‐directed thrust propagation and south‐directed intracontinental subduction, was the dominant mechanism for basin‐ and mountain‐building processes; (2) the stage of Late Cretaceous‐Paleogene deep‐level detachment‐slow uplift and homogeneous subsidence, when the dominant mechanism for the basin‐ and mountain‐forming processes was detachment (subhorizontal north‐directed deep‐level ductile shear) and its resulting lateral propagation of deep material; and (3) the stage of Neogene‐present compression‐rapid uplift and strong subsidence, when the basin‐ and mountain‐forming processes were simultaneously controlled by north‐vergent thrust propagation and compression. The authors summarize the processes as the “ramping‐detachment‐compression basin‐ and mountain‐forming dynamic model”. The basin‐range tectonics was initiated in the Late Jurassic, the Miocene‐Pliocene were a major transition period for the basin‐ and mountain‐forming mechanism and the terminal early Pleistocene tectonic movement in the main laid a foundation for the basin‐and‐mountain tectonic framework in the West Kunlun‐southern Tarim basin margin.