Keyes, C.R., 1939, Why Pennsylvanian series occurs not in Grand Canyon region: Pan-American Geologist, v. 71, no. 2, p. 153-157.
Keyes, C.R.
Pan-American Geologist, v. 71, no. 2, p. 153-157.
Paleoenvironment, Paleogeography, Tectonics, Sedimentary, [Supai Fm][Supai Group] - Pennsylvanian/Permian, (Aubrey Group) - Permian,