Abstract: FengYG alluvial fan is a large fan that lies to the northwest of Taiyuan basin. It has a widen plan view. Exposures with typical parallel bedding sediments were found at fanhead. It shows that FengYG alluvial fan is mainly formed by upper flow regime sheetflood process. Sheetflood deposits comprise pebble to granule gravel bar deposits with small thickness that extend far on side directions, and between bar deposits with finer grain size. Geomorphic and geologic features of its drainage basin shows that larger accommodation space formed by uplift of Lüliang mountain possibly led to sheetflood deposits on FengYG alluvial fan.

Key words: alluvial fan, sheetflood deposition, Taiyuan Basin

摘要： 风峪沟冲积扇位于太原盆地西北侧，面积较大，平面形态十分开阔。野外考察表明，在该冲积扇顶部出露了典型的、具平行层理结构的沉积物剖面。说明该冲积扇主要由高流态的片流过程形成的。片流沉积物由厚度小、侧向延伸长的中、细砾石坝沉积物和相对粒度较细的坝间沉积物所组成。风峪沟冲积扇流域的地质地貌特征表明，由于该段吕梁山地较大幅度的抬升给冲积扇的发育提供了充分的可容空间，这可能是风峪沟冲积扇上片流沉积物发育的主要原因。

关键词: 冲积扇, 片流沉积, 太原盆地