青藏高原羌塘盆地南部古近纪逆冲推覆构造系统

西藏羌塘地块南部古近纪发育肖茶卡-双湖逆冲推覆构造、多玛-其香错逆冲推覆构造、赛布错-扎加藏布逆冲推覆构造,构成古近纪大型逆冲推覆构造系统。沿逆冲推覆构造的前锋断层,二叠系白云岩与大理岩化灰岩、三叠系砂岩与页岩、侏罗系碎屑岩与碳酸盐岩和三叠纪—侏罗纪蛇绿岩自北向南逆冲推覆于古近纪红色砂砾岩之上,形成规模不等的构造岩片与飞来峰。羌塘盆地南部主要的逆冲断层和下伏的褶皱红层被中新世湖相沉积地层角度不整合覆盖,表明逆冲推覆构造运动自中新世以来基本停止活动。羌塘盆地南部古近纪逆冲推覆构造运动在近南北方向产生的最小位移为90km,指示新生代早期上地壳缩短率约为47%。古近纪逆冲推覆构造对羌塘盆地油气资源具有重要影响。

Paleogene thrust system in southern Qiangtang basin, central Tibetan Plateau

A large-scale thrust system was formed in Paleogene, which included Xiaochaka-Shuanghu thrust, Duoma-Qixiang Co thrust and Saibu Co-Zagya thrust in southern Qiangtang basin. Permian marbleized limestone and dolomite, Triassic sandstone and shale, Jurassic clastic rocks and carbonate rocks and Triassic-Jurassic ophiolite were thrusted southward over Paleogene red-beds along frontier faults of each thrust, forming tectonic slices, outliers and nappes of Permian-Jurassic rocks overlying Paleogene red-beds in north, central and south Qiangtang basin. Miocene lacustrine deposits of weak deformation lying unconformably over major thrust faults indicate that major thrust faults have stopped activity since Miocene in southern Qiangtang basin. Minimal estimation of southward thrust displacement in Paleogene is ~90km, corresponding to ~47% upper crust shortening of southern Qiangtang block. The Paleogene thrust system played an important role in the formation and preservation of oil-gas in southern Qiangtang basin.