The group is a single regression-transgression sequence in its type location in the San Juan Basin, dividing the older marine Mancos Shale and younger Lewis Shale deposited in the Western Interior Seaway. The Point Lookout Sandstone represents the regression, the Menefee Formation the subsequent fluvial delta deposits, and the Cliff House Sandstone the return of the sea. In other locations, such as along the Book Cliffs, the picture is more complicated, with multiple regression-transgression sequences from tectonic activity along the Sevier mountain front. In the Cody area, the group is a simple regression sequence and remains at formation rank. Here the group is described as interbedded light gray sandstone and gray shale in the upper part; massive, light-buff, ledge-forming sandstone containing thin lenticular coal beds in the lower part.

Source
Wikipedia