摘要
榆木山地处祁连山北缘与河西走廊南缘的盆山结合带,是青藏高原北缘高原隆升与扩展的关键构造带。野外地质调查与构造填图发现,祁连山北缘的榆木山地区发育大型逆冲推覆构造,逆冲推覆构造之下是被掩埋的、褶皱了的早白垩世早期沉积地层,并被随后的走滑断裂活动和走滑双重构造所改造。深地震反射和大地电磁剖面测量与解释的初步结果,验证了祁连山北缘断裂以北发育的逆冲推覆构造,榆木山北缘山系构成飞来峰构造,将早白垩世酒泉盆地的一个分支掩盖在前中生代地层之下。构造关系分析给出主期逆冲推覆作用的时限大致为早白垩世早期,反映了在新生代印度—亚洲碰撞之前存在一期强烈的晚中生代构造挤压事件。逆冲推覆构造之下发现白垩纪盆地油气显示,扩展了该地区油气前景。
The Yumu Mountain is located in the basin-mountain junction zone between the northern margin of the Qilian Mountains and the southern margin of the Hexi Corridor basin. It is a critical tectonic feature for the understanding of the uplift and expansion of the Tibetan Plateau on its northeastern margin. Field geological survey and structural mapping revealed the large-scale overthrust and nappe structure in the Yumu Mountain area as well as buried and folded Early Cretaceous sedimentary strata in the foot wall. The overthrust and nappe structure was modified by subsequent strike-sliping and strike-slip related duplex. Preliminary results from deep seismic reflection profiling and magnetotelluric(MT) sounding validate the thrust-nappe structure and the existence of Early Cretaceous basin, a branch of the Jiuquan Basin, buried underneath the Yumu Mountain klippe.Structural relationship analysis shows that the major Yumu Mountain nappe was formed approximately in the early period of Early Cretaceous, which reflects a strong tectonic compression in the late Mesozoic before the Cenozoic Indian-Asian collision. The discovery of oil and gas expands promising oil and gas prospects in Cretaceous strata underneath the Yumu Mountain nappe.