Salt Core, Pinal County, Arizona | Salt core from exploration drilling by El Paso Natural Gas in the Picacho Basin near Eloy. A salt deposit ranging from 1,000 to 4,000 feet thick is encountered about 1,800 feet below the ground surface. (Photo by Keenan Murray)
The salt was originally precipitated from an enclosed basin-wide lake where evaporation outstripped recharge. As a result the lake was cyclically saturated in salt, which precipitated and fell out of solution.
For more on salt in Arizona, see Steve Rauzi's (2002), 'Arizona has salt'. http://repository.azgs.az.gov/uri_gin/azgs/dlio/1075
