A brief study of the areal distribution of the various rock types of the Wasatch formation in the Powder River Basin, Wyoming, was made during the summer of 1952. In the south and central parts if the basin, the Wasatch formation appears to contain coarser-grained rocks in contrast to the northern part, which contain relatively no coarser-grained rocks. The finer-grained rocks are abundant in the northern and central parts of the basin but relatively scare in the southern part. The known uranium deposits in the Wasatch are in the central area where coarser-grained sandstones are complemented by abundant finer-grained rocks such as shales and siltstones.