Face Mountain and Oatman Mountain·are located approximately 25 miles northwest of the town of Gila Bend and about 15 miles north of the town of Sentinel, in southwestern Maricopa County, Arizona. They are actually two large buttes which rise just over 1000 feet above the surrounding plain. The study area is within portions of the Yellow Medicine Butte Quadrangle (1:24,000), the Quail Spring Wash Quadrangle (1:24,000), the Oatman Mountain Quadrangle (1 :24,000) and the Dendora Valley Quadrangle (1:24,000). The bedrock of the two mountains consists almost entirely of basalt. Geologic map of Face Moutain and Oatman Mountain, south-central Gila Bend Mountains, Maricopa County, Arizona, Scale 1:50,000