阿尔金山北麓晚新生代沉积物磁组构特征及其地质意义

阿尔金山北麓晚新生代沉积物比较敏感地记录了阿尔金山构造活动的历史.通过对若羌米兰河口剖面晚新生代沉积物沉积学和磁组构特征分析,发现中新世晚期以来该区地层沉积变化明显,岩石磁化率椭球体以压扁为主,磁面理发育,磁化率椭球体最小轴方向为NNE-SSW和NNW-SSE,推测阿尔金山晚新生代以来可能至少经历了中新世末-上新世初、晚上新世和中更新世三次重大构造活动历史.根据磁化率各向异性最小轴方向的变化,结合地层不整合关系、沉积物砾石成分和古水流方向变化以及区域研究成果,表明若羌一带地块晚上新世以来发生阶段性逆时针旋转,推断阿尔金断裂构造带的左走滑特征可能形成于晚上新世以后.

Characteristics of the magnetic fabric of sediments in the northern margin of Altun Tagh mountain since the late Cenozoic and its geological significance

The late Cenozoic sediments in the northern piedmont of Altun Tagh range exhibited the signals of tectonic process of the mountain. These sediments, 980 m in thickness, can be divided into four parts from bottom to top based on the three unconformities between them. The lowermost is lacustine, the second part is fan-delta and the third and forth parts are fluvial, which belong to the Middle Miocene, Late-Miocene, Pliocene and Middle Pleistocene respectively. The analyses of Cenozoic sediments of Ruoqiang-Milan section and measurement of its anisotropic magnetic susceptibility(AMS) show that magnetic ellipsoids are oblate and he minimum axis directions are mostly NNW, SN and NW, subsequently, implying the Ruoqian region has rotated anticlockwise since the late Pliocene and Altun Tagh mountain probably underwent three stages of tectonic uplift that might have happened in late Miocene, late Pliocene and middle Pleistocene.