undifferentiated rock units

Paleontology and geology

In the Early Devonian, the seas began to return to Alberta, and very shallow waters spread over parts of the province. Reddish-colored sandstones, dolostones, salt, and gypsum deposits formed in the beaches, mudflats, and lagoons. For a time, the waters got deeper, but in the Middle Devonian, a large barrier reef developed to the northwest, restricting the flow of water over the province. As the seawater evaporated, more salt, gypsum, and sandstone deposits formed. When the barrier came down, seawater spread over the province. The tropical seas of this period were home to brachiopods, crinoids, trilobites, conodonts, gastropods, bivalves, sponges, corals, and stromatoporoids. Their fossils are preserved in rocks below the surface, as well as in outcrops in the northeast and Rocky Mountains. The small exposures in the Rockies also preserve bone fragments of early armored fish and sharks.