Based on grain size analysis of the sediment from Borehole YE07 at the depth of 900 m in the Yinchuan Plain of Northwest China and with reference to previous data,the evolution process of depositional environment in the Yinchuan Plain was studied since the middle Pleistocene.The results indicated that the main changes of depositional environment in the study area were mainly controlled by climate,geological structures,and evolution process,which showed distinct regional characteristics underwent the following evolution stages:1) lacustrine deposition during 722-664 ka B.P.;2) mainly fluvial deposition during 664-126 ka B.P.,with stronger hydrodynamic conditions and higher kinetic energy;3) fluvio-lacustrine alternating deposition with the fluvial deposition as the main during 126-11 ka B.P.;and 4) mainly fluvio-lacustrine deposition since 11 ka B.P..This research provid a new theoretical foundation for the study of hydrogeology and the division of quaternary sediments in the Yinchuan Plain.%本文通过对银川平原深达900米的YE07钻孔沉积物进行粒度分析,结合其他钻孔的研究资料,探讨了银川平原中更新世以来沉积环境的演化过程,发现银川平原沉积环境的变化主要受气候和构造因素的影响,其演化过程表现出一定的区域特点,主要经历了以下的演化阶段:722～664 kaB.P.属于湖沼相沉积;664～126 ka B.P.沉积环境以河流相沉积为主,水动力条件较强,沉积动能较高;126 ～ 11 kaB.P.的沉积环境是以河流相为主的河湖交替相;11 ka B.P.以来沉积环境主要表现为河湖相沉积.银川平原沉积环境的研究为其水文地质研究和第四纪地层划分提供新的理论依据.
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