The formation is not especially productive in this region. Marine shells are numerous in some localities, and bones of marine reptiles have been found at various places. As usually seen, it is almost entirely composed of impure clay shales, very dark, brownish-gray to almost black, and commonly interbedded with thin patches of white bentonite, yellow ochre, gypsum, and limestone.
Dakota.
This formation produces the high hogback which is usually present some distance east of the Red Rocks. There are generally two or three layers of massive, light-colored sandstone separated by clays which are used extensively in the making of bricks and pottery. Leaf impressions and some fish scales are found in the clays and occasionally in the sandstone. The hogback is a good marker from which to locate other formations, because of its prominence in the foothills landscape.
Morrison.
Good dinosaur material has been taken from the Canon City and Morrison districts. The formation is to be found on the lower west slope of the Dakota hogback. It consists of continental deposits of the stream and lake types. There is considerable sandstone in this formation and a little limestone is to be found here and there, but the most characteristic feature is in the shales. When freshly exposed, the shales are delicately tinted with gray, green, and maroon, a bronze-green being rather prominent. This formation is highly variable in character, with much of the clay often buried under the valley floor. In addition to the bones of reptiles, there are plant fossils, usually of poor quality, and fresh-water gastropods more or less abundant in some localities.
Lykins.
Outcrops are not prominent, owing to the small amount of weather-resisting materials. The sandy clays are commonly of a deep red color mottled with spots of light gray. A white limestone is sometimes present near the middle of these deposits, and gypsum beds are included locally. The formation is often indicated only by red soil in the depressions between ridges. Few fossils have been reported.
Lyons.
This formation is usually prominent as the eastern wall of the uplifted Red Rocks series. In some localities it forms a ridge of pink or white sandstone distinctly separated from the older sediments to the west. Very few fossils are found.