Geologic Map of the Stewart Mountain Quadrangle, Maricopa County, Arizona

This map depicts both the bedrock geology and the general ages and distribution of Late Tertiary and Quaternary deposits and geomorphic surfaces in the Stewart Mountain quadrangle (see Figure 1). The Salt River, re-emerging from Saguaro Lake, slices through the middle of the study area where it separates granite pediment and of the Usery and Goldfield Mountains (respectively) to the south, from a vast expanse of Late Tertiary basin-fill sediments to the north. Mapping of the surficial deposits was based both on field observations and interpretation of color 1:30,000-scale aerial photographs (dated 6-12-88), obtained from the Tonto National Forest in Phoenix. All of the region is administered by the Tonto National Forest. Good access to the region is provided by State Route 87, the Bush Highway, and Usery Pass Road (see Figure 2). A primitive road provides access to Bulldog Canyon, but locked gates at both ends can only be opened by obtaining a permit from the Tonto National Forest Service field office in Mesa. However, even with a 4-wheel drive vehicle, the road is almost impassable in places. Saguaro Lake is a popular recreation area and the roads to the west shore and to Butcher Jones Cove are paved. At the Saguaro Lake marina boats are available for rent that will provide the only access to the northeast side of the Goldfield Mountains.