Structural measurements of deformation fabrics in Paleoproterozoic rocks within the map area were plotted on stereonets using Rick Allmendinger’s Stereonet software provided on his Cornell University website (www.geo.cornell.edu/geology/faculty/RWA/programs.html). One map sheet and a second sheet with geochemical data and plots, structural stereonets and three cross-sections.

The Peppersauce Wash 7 ½' Quadrangle and the southwestern part of the Kielberg Canyon 7 ½' Quadrangle include part of the San Pedro River lowlands, flanking valley fill on both sides of the river, and limited bedrock outcrops (Fig. 1). Production of this new geologic map continues the Arizona Geological Survey mapping program of the San Pedro River valley. This mapping was done under the joint State-Federal STATEMAP program, as specified in the National Geologic Mapping Act of 1992, and was jointly funded by the Arizona Geological Survey and the U.S. Geological Survey under STATEMAP Program Contract award number 07HQAG0110. Mapping was developed from previous mapping, new field investigations, and interpretation of color orthophotography taken in 2007. Mapping was compiled digitally using ESRI ArcGIS software.

The Clark Ranch 7½' Quadrangle and the western half of the Rhodes Peak 7½' Quadrangle include part of the San Pedro River, flanking valley fill, and bedrock on the east side of the valley that forms part of the Galiuro Mountains range front (Fig. 1). Production of this new geologic map continues the Arizona Geological Survey mapping program of the San Pedro River valley. This mapping was done under the joint State-Federal STATEMAP program, as specified in the National Geologic Mapping Act of 1992, and was jointly funded by the Arizona Geological Survey and the U.S. Geological Survey under STATEMAP Program Contract award number 07HQAG0110. Mapping was compiled digitally using ESRI ArcGIS software. Parts of the Clark Ranch and Rhodes Peak Quadrangles were mapped previously by Creasey et al. (1961), Dickinson (1987, 1991, 1998), Marsh (2001), and Skotnicki (undated)). Studies of Cenozoic sedimentary strata in the Clark Ranch 7½' Quadrangle include those by Blake (1902, 1903), Bollaert (1952, 1953, 1962), Heindl (1963), Agenbroad (1967), Krieger et al. (1974), Ladd (1975), Scarborough and Wilt (1979), Utley (1980), Lindsay (1984), Dickinson (1988), Shenk (1990), and Dickinson (2003). The regional geochronology of the Oligo-Miocene volcanic rocks is outlined by Dickinson and Shafiqullah (1989). Studies of the Copper Canyon mineral district include those by Marsh (2001), Creasey et al., (1981), Guthrie (1994), Guthrie and Moore (1978), Hausen et al. (1988), Walker (1979) and Eichenlaub and Seedorff (2008).

The Lookout Mountain 7½' Quadrangle includes part of the San Pedro River lowlands, flanking valley fill, and bedrock on the west side of the valley that forms the eastern Black Hills and southeastern-most Tortilla Mountains (Fig. 1). Production of this new geologic map continues the Arizona Geological Survey mapping program of the San Pedro River valley. This mapping was done under the joint State-Federal STATEMAP program, as specified in the National Geologic Mapping Act of 1992, and was jointly funded by the Arizona Geological Survey and the U.S. Geological Survey under STATEMAP Program Contract award number 07HQAG0110. Mapping was compiled digitally using ESRI ArcGIS software. Plate 1 contains two cross sections.

These geologic map sheets and report encompass the proposed State Route 95 Relocation Corridor in Mohave Valley, western Arizona, between the Black Mountains on the east and the Colorado River on the west (Figure 1). The maps were developed through compilation of existing geologic mapping and extensive new geologic mapping. The map area includes a portion of the historical floodplain of the Colorado River, a broad swath of the piedmont east of the river, parts of western flank of the Black Mountains, the channels and terraces of Sacramento Wash, and the northernmost piedmont of the Mohave Mountains (the Powell Mountain area). The corridor is predominantly covered with late Miocene and younger alluvium deposited by local tributary washes and the Colorado River. Deposits range in age from modern to at least 8 Ma (millions of years ago), and deposit characteristics and composition vary substantially depending on whether they were emplaced by the modern Colorado River, older versions of the river, or tributary washes derived from the Black Mountains or the northern end of the Mohave Mountains. The northern, northeastern, and southernmost parts of the map include a variety of bedrock types ranging in age from early Proterozoic to middle Miocene. This map and report describe the physical characteristics of geologic units of different ages and sources, the mapped extent of various geologic units, and potential geologic resource and geologic hazard implications of this mapping. These maps include modified versions of portions of several published maps that have been completed in this area since 1997 (Howard et al., 1997; Howard et al., 1999; Faulds et al., 2001; Murphy et al., 2004; Pearthree and House, 2005; Pearthree, 2007; Spencer et al., 2007; Malmon, in review). Extensive new surficial geologic mapping and bedrock mapping was done where needed.

This report and accompanying maps describe the geology, geomorphology, and geologic hazards of the Maricopa area in western Pinal County, central Arizona. This mapping covers all of the Antelope Peak NE 7 ½’ quadrangle and most of the Maricopa 7 ½’, and includes the community of Maricopa (Figure 1). The map area encompasses part of the basin floor occupied by Santa Rosa Wash and the Santa Cruz River, the gently sloping piedmonts flanking the west side of the basin floor, and a few bedrock hills (inselbergs) outboard from the Haley Hills, Palo Verde Mountains and Table Top Mountains to the west and southwest of the map area. Agricultural activity and more recently urban development have substantially modified the surface of the basin floor and most of the piedmont areas. Maricopa is developing into a significant population center and rapid development is occurring on the basin floor and the piedmont in the northern part of the map area. The map area includes part of the Maricopa- Stanfield sedimentary basin, from which tremendous amounts of ground water have been extracted primarily for agricultural purposes

The Redington 7 ½' Quadrangle includes part of the northern San Pedro River and flanking valley fill, as well as two areas of bedrock on the east side of the valley (Figure 1). Production of this new geologic map continues the Arizona Geological Survey mapping program in the San Pedro River valley, and complements geologic mapping to the south of this quadrangle. The map area is located within the San Pedro River valley in the Basin and Range Province of southeastern Arizona. Oligocene to early Miocene, compositionally diverse volcanism in the Galiuro Mountains to the east of the map area occurred during the initiation of a period of severe tectonic extension that uncovered the Catalina-Rincon metamorphic core complex to the southwest (Dickinson and Shafiqullah, 1989; Dickinson, 1991). The San Pedro Valley was created in its basic form by this period of extensional faulting, which largely ended in the early to middle Miocene. Relative to this period of severe faulting, minor faulting affected the valley during late Miocene to Quaternary time, probably with declining activity over this time period. Laramide (latest Cretaceous to earliest Tertiary), steeply southwest dipping to locally overturned volcanic and sedimentary rocks are exposed over part of Redfield Canyon. These are overlain by gently dipping Oligocene to early Miocene Galiuro Volcanics. Tilting of the Laramide strata is thought to be Laramide, not middle Tertiary, because Galiuro Volcanics participated in the middle Tertiary extensional faulting in those areas where faulting occurred, and the Galiuro Volcanics that overlie the Laramide strata are only slightly tilted (Dickinson, 1991).

This map depicts the geology of the Hereford and the northern part of the Stark 7 ½' quadrangles, which are located in the upper San Pedro Valley north of the U.S. - Mexico border. The quadrangles cover much of the piedmont east of the San Pedro River and southwest of Mule Mountains, including a portion of the San Pedro Riparian National Conservation Area along the river. The map also covers a small portion of the piedmont west of the San Pedro River. The geology of the quadrangle is diverse and includes Paleozoic sedimentary and igneous rocks, exposures of the upper part of the late Cenozoic basin-filling deposits, and Quaternary surficial alluvium deposited by tributary streams and the San Pedro River. Bedrock geologic mapping was compiled from Ferguson and Johnson (2006). This map is one of several 1:24,000-scale geologic maps that have been completed recently in the upper San Pedro Valley. Other maps cover the Lewis Springs (Pearthree et al., 2006), Fairbank (Ferguson et al, 2006), Land (Shipman and Ferguson, 2005), St. David (Youberg, 2005), Huachuca City (Pearthree, 2003), McGrew Spring (Shipman and Ferguson, 2003), and Benson (Youberg et al, 2004) quadrangles. This mapping was completed under the joint State-Federal STATEMAP program, as specified in the National Geologic Mapping Act of 1992.

This map depicts the geology of the Fortuna 7 ½' Quadrangle and about 2.5 square miles of the northern end of the Gila Mountains that is in the adjacent Laguna Dam, Dome, and Ligurta 7 ½' Quadrangles. The map area encompasses the northwestern Gila Mountains and the broad Gila River valley between the northern Gila Mountains and Yuma, in the southwestern corner of Arizona. The quadrangle covers bedrock in the northwestern Gila Mountains, much of the western piedmont at the foot of the northwestern Gila Mountains, and alluvial sediments deposited by the Gila and Colorado Rivers. Large, active gravel quarries, and the historic Dome placer gold district, are within the map area at the foot of the Gila Mountains. This mapping was completed under the joint State-Federal STATEMAP program, as specified in the National Geologic Mapping Act of 1992.

Abstract: The Flatiron Mountain 7.5' Quadrangle is located approximately 70 km (40 miles) west of downtown Phoenix, and is just north of Interstate Highway 10. The map area includes the southeastern part of the Belmont Mountains and many isolated bedrock hills south and southeast of the Belmont Mountains. Most of the quadrangle, however, is underlain by Quaternary surficial deposits. Jackrabbit and Coyote washes, heading in the proximal piedmonts of the Big Horn Mountain northwest of the study area, are the major drainages. Jackrabbit Wash is incised up to four meters into older Pleistocene deposits. Coyote Wash flows around the Belmont Mountains and diverges into multiple channels to the south. The channels and floodplains of Coyote Wash are less incised than Jackrabbit Wash. Smaller tributary washes on adjacent older Pleistocene deposits generally are not incised more than two meters. Older Hassayampa River deposits are found along the eastern side of the quadrangle.