Permian salt in the Holbrook Basin, Arizona. The northwest-southeast trending Holbrook Basin embraces an area of thickened Permian sedimentary rocks located in east-central Arizona near the south margin of the Colorado Plateau. The Basin lies between two positive tending regions, the Mogollon Rim to the southwest and the Defiance region to the northeast. Evaporite deposits of principal interest occur in the ''upper'' Supai Formation between the Fort Apache Member of the Supai Formation and the Coconino Sandstone. The upper Supai ranges from 450 to 1300 feet in thickness and in its thicker portions contains an aggregate thickness of evaporite, largely halite, of up to 485 feet. Subsurface halite occurs over an area of about 2300 square miles. One plate,scale 1:25,000.