西藏当雄地区构造地貌及形成演化过程

The Formation and Evolution of Tectonic Landform of Damxung Area in Central Tibetan Plateau

西藏当雄地区在区域性挤压缩短期后发育 2种典型层状地貌面 ,即山顶面与盆地面 ,不同地块具有不同特点与不同高度的山顶面。山顶面形态与分区性、分段性明显受早期逆冲推覆构造与晚期断裂所控制 ,山顶面梯级带对应于区域张性 张扭性断裂与盆 山构造 地貌边界。原始山顶面或高原主夷平面主要形成于 15～ 8Ma ,念青唐古拉山脉开始快速隆升与两侧地块初始断陷时代为 8～ 4Ma ,羊八井 当雄 谷露盆地快速裂陷事件发生于 2～ 1.5Ma ,区域NW向走滑断裂与现今河流峡谷主要形成于 1.4Ma以来。当雄及邻区层状地貌面的形成。

After the NS trending compression and crust shortening in late Oligocene early Miocene, the Damxung area in central Tibetan Plateau formed two types of planar landform surfaces, i.e., the summit surface resulting from regional erosion planation and the basin surface resulting from depression deposition of rifted basins. Summit surfaces of different mountainous blocks have different landforms and different ranges of altitude, and grading belts of summit surfaces corresponding to shear extensional boundary faults often appear as the division of basin and range. The original summit surface or regional planation surface was mainly formed in 15～8 Ma, followed by extensional faulting and rapid uplifting of Nyainqentanghla mountains in 8～4 Ma. The Yangbajain Damxung rift belt began to form high angular normal faulting and rifted depression in 2～1.5 Ma, followed by NW trending strike slip faulting and formation of the present day river system since 1.4 Ma or so. The formation, splitting and evolution of regional planar landform surfaces of Damxung area represent well the geodynamic process of regional tectonic activity and landform changes of central Tibetan Plateau in late Cenozoic Era.