That part of the Colorado Plateau where the states of Arizona, New Mexico, Utah, and Colorado come together has been called "the Four Corners."
Investigation of the late Paleozoic stratigraphy of this region was stimulated by the discovery of oil in the Paradox Basin.
The Paradox Basin Province is in southeastern and south-central Utah and southwestern Colorado. It is an evaporative basin of Pennsylvanian age in Southeastern Utah and Southwestern Colorado that also touches the states of Arizona and New Mexico.
Erosion of uplands resulting from the Uncompahgre Uplift produced the coarse, arkosic clastics at the northeastern side of the cross-section. These clastics merge with evaporites of the Paradox basin and then carbonates of the Paradox shelf. Reeflike masses or calcareous algae called algal boherms occur within the carbonate section. Because of their porosity, petroleum and natural gas have accumulated in many of the bioherms.