Late Oligocene-Early Miocene Thrusting in Southern East Kunlun Mountains, Northern Tibetan Plateau

Southward thrusting occurred in Late Oligocene-Early Miocene in southern East Kunlun （昆仑） Mountains formed the South Kunlun thrust （SKT）. Permian strata and Triassic rocks were thrusted over the Paleocene-Eocene red-beds of Fenghuoshan （风火山） Group and Oligocene brownish red conglomerate and sandstone of Yaxicuo （雅西错） Group along SKT faults, formed tectonic slices, low-angle thrust faults, multi-scaled outliers, and nappe structures in south of Middle Kunlun fault （MKF）. In addition, SKT displacement or shortening is estimated to be -（30-35） km across Dongdatan （东大滩） valley and East Wenquan （温泉） basin. 39Ar-40Ar dating of chlorite of ductile shear zone along front thrust fault indicates that SKT thrusting occurred at 26.5±2.7 Ma, and fission track dating of apatite from mylonitic granite in SKT gives the age 26±2 Ma, corresponding to initial time of rapid uplift of East Kunlun Mountains. Thrust faults and folds of SKT were covered unconformably by Late Miocene lacustrine strata, and major thrusting of SKT ended before 13.5-14.5 Ma according to regional chronological data in northern Tibetan plateau.