青藏高原腹地班戈—双湖一带晚新生代伸展构造及动力学机制

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

在青藏高原腹地,晚新生代以来除发育南北向的伸展构造以外,还发现有一系列时代较新的近东西向正断层控制的伸展构造,空间上呈现出平行排列的宽缓凹槽及其间相对狭窄的山梁相互间隔的活动地貌结构特点,称这种地貌结构为"槽梁地貌"。数字高程模型(DEM)的研究表明,研究区近东西向的伸展构造在地貌上切割了近南北向的双湖盆地。结合断层运动学、年代学及盆地沉积作用的研究,认为近东西向的伸展构造的发育最早可能始于中新世,与近南北向的伸展构造交织发育,断裂的活动性在第四纪随着高原腹地海拔抬升得到了显著的增强。青藏高原隆升后重力作用导致了不同方向断陷盆地的发育。

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, chronolo- gy and sedimentation in the fanlt-controUed 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.