Abstract

Lower Permian (pre-Coconino) rocks are exposed in four separated geographic regions, the Grand Canyon, Mogollon Rim, Defiance Upwarp, and Monument Upwarp, on the southern Colorado Plateau. Physical correlation within and between the regions demonstrates that Lower Permian rocks were deposited in three discrete episodes, each related to separate tectonic and sedimentological controls. The Wolfcampian sandstone sequence comprises the Cedar Mesa and Esplanade sandstones and Halgaito Formation and was deposited in a variety of marine and paralic environments associated with shelves and embayments to the east of the Cordilleran Miogeosyncline. The sequence is not recognizable in the southeastern portion of the study area. The Wolfcampian and Leonardian redbed sequence was deposited across the entire area of study by fluvial and possible paralic processes and includes the Hermit and Organ Rock formations. Correlations used in this study indicate this sequence is present in two areas where it has previously been incorrectly assigned to the Supai Formation: the Mogollon Rim and Defiance Upwarp. The Leonardian Sandstone and Redbed Sequence is confined to the southeastern portion of the study area associated with the Holbrook Basin. Complex marine, paralic, and continental deposition of the DeChelly Sandstone and Schnebly Hill formation (informal) comprises the sequence. The Schnebly Hill formation, though previously included in the Supai Formation, is much younger than the type Supai and is not present in the Grand Canyon.

Terminology of this report restricts the usage of Supai (Group) to Pennsylvanian and lowest Permian rocks of the Grand Canyon and central and western Mogollon Rim. Previous assignments of rocks assigned to the Supai in the eastern Mogollon Rim and Defiance Upwarp are shown to be incorrect and the units are assigned to the Hermit, Organ Rock, and Schnebly Hill formations.