Robert J. Miller

An evaluation of sand and gravel resources in and near the Prescott National Forest in the Verde Valley, Arizona; with a section on evaluation of sand and gravel resources using selected engineering variables

NON-TECHNICAL SUMMARY This study was based on available published literature. Although no field investigation was conducted in the Prescott National Forest to the west of the Verde River, a field investigation was conducted in the summer of 1994 by this author on the Coconino National Forest, to the east of the Verde River, where units of surficial materials of the same age and similar character are found (Cox, 1995). The intent of this evaluation of sand and gravel resources in the Prescott National Forest and adjacent areas in the Verde Valley, is to provide the land managers of the U.S. Forest Service with a map that delineates sandand gravel-bearing geologic units. The map distinguishes (1) sandand gravel-bearing units that are limited to channels from those that are not, (2) sandand gravel-bearing units that are thin (generally less than 40 feet thick which is one contour interval on the topographic maps) from those that are locally thick (generally 40 feet or more), (3) sandand gravel-bearing units that are poorly sorted from those that are well-sorted4, (4) sandand gravel-bearing units that have little or no soil development from those that have greater degrees of soil development and lithification, (5) and sandand gravel-bearing units that support riparian vegetation from those that do not. These distinctive characteristics are related to the geologic age or depositional setting of the rock materials and can be distinguished where areas are mapped in detail. 4 Deposits of sand and gravel are usually more desirable for commercial development if not too well sorted (J. Bliss).

Mineral resources of the Eagletail Mountains Wilderness Study Area, La Paz, Maricopa, and Yuma counties, Arizona

The Eagletail Mountains Wilderness Study Area (AZ-020-128) encompasses most of the Eagletail Mountains and parts of adjoining alluvium-filled valleys. At the request of the U.S. Bureau of Land Management, mineral surveys were conducted on 78,020 acres of the wilderness study area. In this report, references to the wilderness study area refer only to that area for which mineral surveys were requested. The U.S. Bureau of Mines and the U.S. Geological Survey carried out fieldwork during 1986 and 1988 to appraise the mineral resources (known) and assess the mineral resource potential (undiscovered) of the study area. No mineral resources were identified within the study area. Several areas have potential for undiscovered resources. One area having moderate potential for silver and lead and low potential for gold, barium, copper, manganese, molybdenum, and zinc resources extends along the length of Cemetery Ridge, which crosses the southwest boundary of the study area. An area northeast of Cemetery Ridge and extending along the south boundary of the study area has low potential for gold, silver, lead, zinc, copper, barium, manganese, and molybdenum resources. One area having moderate and an adjacent area having low potential for gold, silver, lead, zinc, and copper resources lie immediately west of and extend into the northwest corner of the study area. An area including the Double Eagle mine in the southeast corner of the study area has moderate potential for silver and low potential for gold, copper, lead, and zinc. An area along the northeast side of the Eagletail Mountains has moderate potential for gold and silver and low potential for lead, zinc, copper, and molybdenum resources. A minor amount of green tuff has been quarried along the northern boundary of Manuscript approved for publication, March 2, 1989. the study area for use as ornamental stone. Two areas within the study area have low potential for further resources of this tuff. The northernmost of the two areas also has low potential for silver. One area southwest of Courthouse Rock near the center of the study area has low potential for perlite. An area along the southwest margin of the study area and an area along the east boundary of the study area are underlain by a thick accumulation of basin-fill sediments. These two areas have low potential for geothermal resources. The entire study area has low potential for oil and gas resources. Sand and gravel is abundant in the study area, but it has no unique properties and adequate resources are available closer to markets. Character and Setting The Eagletail Mountains Wilderness Study Area comprises 78,020 acres in southwest Arizona, between Phoenix and Quartzite and about 4 mi south of Interstate 10 (fig. 1). The study area includes most of the Eagletail Mountains as well as parts of the surrounding pediments and alluviumfilled valleys. Topography is extremely rugged in the main part of the Eagletail Mountains but subdued to nearly flat in the valleys and on pediments that underlie much of the study area. Elevations range from 3,043 ft on Eagletail Peak to approximately 1,300 ft in the lower parts of adjoining valleys. The pediments are underlain predominantly by crystalline rocks of Proterozoic and (or) Mesozoic age (see appendixes for geologic time chart). Upper OIigocene(?)to Miocene-age basaltic to rhyolitic lava flows and tuffs overlie the crystalline rocks and constitute the topographically high part of the range. Faulting occurred during and following volcanism and is primarily responsible for the northwest trend of the range. Mineral Resources of the Eagletail Mountains Wilderness Study Area, Arizona C1