通过对山西榆社盆地新近系中新统马会组砾岩层的分布特征、剖面特征和砾组特征分析,结合盆地内部和四周山区的岩性特征分析,阐述了砾岩层本身的性质、成因、来源和搬运方式等,探讨砾石沉积时盆地的水动力条件、气候环境、地貌特征和构造条件等.研究表明,马会组砾岩层为榆社盆地新近纪河湖相沉积的底砾岩,其中所含的3层砾岩在成因、来源、搬运和沉积环境上具有较好的一致性.马会组砾岩层为多期次、多来源、非稳定的冲湖积成因,为湖泊水进期的沉积物,指示干冷向温湿转变的气候环境；砾石的主要来源是盆地内部的基底地层及其东缘、北缘和西缘的山区；砾石遭受了较强的物理化学作用,还存在一定的生物作用；含量较少的花岗岩砾石经受了较长距离的搬运,其他岩性砾石经受了近—中距离的搬运.榆社盆地为喜马拉雅运动二幕晋东地区山地相对抬升形成的山间盆地,砾石沉积时已形成了中间低、四周高的盆地雏形.%Based on the analysis of gravel fabric characteristics of conglomerate layers of the Middle Neogene Mahui Formation in Yushe basin, combined with the lithological study of basin basement and its adjacent mountains, this paper deals with the origins, sources, hydrodynamic conditions, climate environment, geomor-phy and tectonics of Yushe basin, Shanxi. The study reveals that Mahui Formation is composed of fluvial and lacustrine basal conglomerate during Neocene, of which three conglomerate layers show better consistency in origins, sources, transport and sedimentary environment. The conglomerate layers of Mahui Formation are multi-periods , multi-sources and unsteady alluvial and lacustrine sediment, which indicates an environment from dry-cold to humid. The gravels underwent strongly physical and chemical weathering and some biological action. The main source rocks of the conglomerate are basement strata of the basin and strata located in the eastern, northern and western margin of the basin. Lower content granite gravels were carried over comparatively long distance. Nevertheless, the majority of gravels underwent near-medium distance transport. A conclusion is drawn that Yushe basin is an intramontane basin formed by relative mountain uplift in the east of Shanxi during the second stage of the Himalayan movement.
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