The following excerpts come from the Arizona Geological Survey, Circular 30 January 2002, Arizona Has Salt! Written by: Steven L. Rauzi:

“Salt was first reported in the Holbrook Basin in the 1920s when it was encountered by cable tool holes drilled for oil and gas. Rauzi (2000) used 223 wells including 135 wells cored for potash and 88 wells drilled for oil, gas, or LPG storage, to depict the extent and thickness of salt in the Holbrook Basin. Only 29 of the wells were drilled through the entire thickness of salt. Most were drilled into only the upper 100 to 300 ft of salt where potash minerals were present.”

“Salt in the Holbrook Basin is part of the Supai Formation of Permian Age. The Supai Formation there consists largely of sabkha deposits of red to reddish-brown clayey siltstone and halite interbedded with anhydrite, gypsum, and carbonate.”