Geologic Map of the West-Central Gila Bend Mountains, Maricopa County, Arizona

The area described in this study includes the central Gila Bend mountains, Maricopa county, Arizona. The study area encompasses the southern one-half of the Cortez Peak Quadrangle (1:24,000) and the northern two-thirds of the Yellow Medicine Butte Quadrangle (1:24,000) (Fig. 1). Bedrock in this area consists largely of Proterozoic metamorphic rocks overlain by an extensive sequence of Miocene mafic and intermediate volcanic rocks and continental clastic rocks (plate 1). Late Oligocene to Early Miocene granitoid plutonic rocks intrude Proterozoic rocks in the northwest part of the map. Sources of map data are shown in Figure 2, rock-unit correlations and relative ages are shown in Figure 3, and map symbols are shown in Table 1.