Late Cenozoic extension structure in Baingoin-Shuanghu area of central Tibet and its dynamic mechanism

In central Tibetan Plateau,besides the NS-tranding extension structure after late Cenozoic,a series of nearly EW-striking extension structures,controlled by EW-trending normal faults,were found during the field work.Geomorphology was characterized by the parallel-relief valleys separated by the relatively narrow ridges and the rift-ridge landform.The DEM analysis shows that the EW-tranding extension structure cutting the NS-trending Shuanghu basin in the study area.Studies of the fault kinematics,chronology and sedimentation in the fault-controlled basin suggest that the activity of the EW-trending normal faults began in the Miocene and these faults were probably developed alternately with the NS-trending extension structure.Furthermore,with the increasing of the elevation of central Tibetan Plateau,the activity of the EW-trending faults were obviously strengthened in Quaternary.The gravity action on the high-standing plateau resulted in the development of grabens in different directions.