宁夏南部晚更新世沉积物沉积特征及其构造意义

摘要

通过研究宁夏南部第四纪沉积物类型及沉积作用,结合沉积物年代学分析,初步确定宁夏南部晚更新世发育众多沉积盆地.其沉积学特征研究表明,晚更新世沉积盆地主要发育冲积扇沉积物、湖相泥质-粉砂质沉积物、盆地边缘斜坡岩相组合、现代河流一级阶地沉积物以及黄土等几种沉积物.沉积作用特点显示,晚更新世沉积盆地的大范围出现主要受构造伸展作用控制,表明青藏高原北东扩展过程中,宁夏南部地区于晚更新世期间还存在较明显的构造伸展活动,从而证实青藏高原隆升及其北东向扩展具明显的阶段性.%The studies of the Quaternary sediments,the sedimentation in southern Ningxia and the Quaternary chronologic dating show many late Pleistocene sedimentary basins occurred in southern Ningxia in the late Pleistocene.The Late Pleistocene sediments in the basins are mainly featured by alluvial fan sediments,lacustrine argillaceous-silty sediments,basin-margin-slope lithofacies associations,first-terrace sediments of modern fluvial and loess sediment.The sedimentation of these basins suggests that the late Pleistocene sedimentary basin was controlled by regionally tectonic extension,which indicates that an obvious tectonic extension affected the southern Ningxia in the northeastward growth and uplift of the Tibetan Plateau,and provides a sedimentological evidence for the phasal uplift of the Tibetan Plateau.