The Picketpost Mountain and Iron Mountain 7.5' quadrangles are located east of the Phoenix metropolitan area and are within the Basin and Range physiographic and tectonic province of southwestern North America (Figure 1). Mapping represented on Plate 1 was done by the authors during the fall and winter of 1994-1995 or was derived from Peterson (1966) for Picketpost Mountain or from field sheets of the Quail Spring area provided by Steve Skotnicki and Charles Ferguson. Most map units are those used in adjacent USGS geologic maps (Peterson, 1960, 1969 ;Theodore and others, 1978; Creasey et aI., 1983; Peterson and Jinks, 1983).