蒋家沟流域在小江大断裂东侧的隆起地段，这一区域构造活动强烈。自第四纪以来，受到内、外动力地质作用的共同影响，蒋家沟在河流沉积及泥石流堆积作用下形成了阶梯状台地。实地考察蒋家沟各支沟残留台地的沉积构造、新鲜坡面的古泥石流活动记录，根据泥石流堆积物的沉积特征，初步划分泥石流类型。再结合现有的泥石流容重计算方法和各泥石流台地泥石流堆积物的颗粒分析实验结果，可计算出蒋家沟不同泥石流活跃期泥石流的天然容重，还原了蒋家沟第四纪以来不同时期泥石流活动特征。最后讨论了泥石流在不同时期发生变化的原因。

 

Jiangjia ravine lies in the uplift block of eastern of Xiaojiang giant fault，with intensity tectonic activity and frequently earthquake． Since the Quaternary period， Jiangjia generated several stepped terrace under the internal and external geological process． Based on field survey of the sedimentary structures of residual terrace and the record of debris flow activities in newly formed free face and the characteristics of ancient debris flows’sediment，the types of debris flows can be confirmed． In addition， the density of ancient debris flows in every period can be calculated by using the gravel and fine particle content of ancient debris flows’samples in different spots． By this study， the features of debris flows in different stages can be found since the Quaternary periods，and the causes was discussed，which were related to the types of ancient debris flows and sediment’s characters．