About 239 samples of cuttings from two boreholes located in Dabou were the subject of sedimentological studies (lithological, granulometric and morphoscopic analysis) in this work. These studies aim to identify the origin of these sediments and to specify the factors and the phenomena which involved in their transport and their deposit during Tertiary-Quaternary. After a detailed lithological description of each sample, the sandy fractions were treated according to conventional particle size methods. The formations traversed in the two wells consist of lateritic clays, yellow clays, clay sands and coarse sands. The analyzed sands are coarse and testify to the différents variations in the energy of the stream that transported the sediments. The hyperbolic granulometric facies is dominant in the study area, indicating a variation in streamflow during sedimentation. The predominantly round to sub-round quartz grains suggest a relatively distal supply source while their blunted blunted appearance suggests a stay in the aquatic environment. The sediments of these two wells are therefore sands of fluviatile origin, deposited in a shallow marine environment.