Regionally the pre-Kaibab Permian section in the southern Butte basin comprises six major lithologic units. The basal Permian limestone is an areally extensive formation, but on a regional scale the other five lithologic units are best considered as lithosomes. Faunas indicate that each lithologic unit was deposited in a rather distinctive environment. The Riepe Spring Limestone was deposited in a fairly shallow, open sea; Rib Hill lithosome in very shallow, open, and restricted basins; Pequop lithosome in a fairly deep, open sea; Arcturus lithosome mainly in very shallow, brackish-water bays on a vast tidal flat; Dry Mountain lithosome in shallow, open bays; and Loray lithosome in brackish and highly saline bays and ponds.

Five time-stratigraphic units (stages) are recognized throughout the Butte basin, so geologic history during Early and Medial Permian time can be interpreted fairly accurately. Little or no terrigenous detrital material was contributed to the basin during stage 1, so almost pure limestone was deposited. Stage 1 closed and stage 2 began with the influx of tremendous amounts of silt and very fine-grained sand from an area on the southeast. Later, the highly calcareous rocks of stage 3 were deposited as the rate of influx of terrigenous detrital material declined. Some sand and silt still were provided by a source at the southeast and a shallow-water, "deltaic" sequence began to be developed in the eastern part of the basin. In the western part of the Butte basin a less extensive "deltai " sequence also was being built. Rocks of stage 4 were deposited in water that was deepening throughout much of the basin. Sand and silt continued to be contributed from a source on the southeast and shallow-water, "deltaic" deposits extended far into the Butte basin. Finally, rocks of stage 5 were deposited at a time when the Butte basin was almost completely cut off from the open sea. Deposition of rocks of stage 5 was terminated by the transgression of the Kaibab sea.