内蒙地轴南缘盖层中逆冲断层的样式及形成机制

内蒙地轴南缘盖层中,发育了多种样式的逆冲断层,如叠瓦式、背冲式、对冲式和楔冲式.这些逆冲断层都发育在基底断裂控制的断陷盆地边缘,并向盆内逆冲。形成发育的过程是:区域拉伸、基底断裂活动和断陷盆地发育→区域挤压、盆缘逆冲断层发育→盆缘进一步隆起、逆冲断层进一步发育。所以区域拉伸和挤压、断陷盆地的发育和盆缘逆冲断层的活动三者密切相关。逆冲作用主要发生于燕山运动时期。

ON STYLES AND MECHANISM OF THRUST ON THE SOUTH MARGIN OF INNER MONGOLIA AXIS

Various styles of thrust developed in the sedimentary cover on the south margin of Inner Mongolia Axis. They are imbricate thrust, fan-shaped thrust, ramp thrust and wedge-shaped thrust. All thrusts occurred on the margins of sedimentary basins, controlled by basement fractures, and were transported from the margins to the center of basin. There are several characteristics,as follows. 1) A great part of thrusts are of small-scale and meso-scale, different from large-scale thrust of orogenic belt. 2 ) Bedding-gliding, particularly gliding along the basement unconformity, plays an important role in thrusting. Under the extensi onal regime, detachment tectonics may occur. 3 ) The strike and transporting directions of thrust depend on the orientations of fracture-controlled basins. 4) Gravity plays an active part in the process of formation and evolution of thrusting. The main epoch of thrusting belongs to the Yanshanian.