The following report is the second compilation of reports describing the geology of the Basin and Range to Colorado Plateau Transition (BARCO) area.

From introduction: The purpose of this study is to establish a stratigraphic framework of the Bisbee Group in the Tombstone Hills, and to use this stratigraphy to unravel the complex history of folding, faulting, intrusion, and mineralization.

The following report is a mineral resource assessment of Coronado National Forest of southeastern Arizona and southwestern New Mexico, formed by geologic, geochemical, and geophysical data.

From introduction: This report supplements similar reports prepared for the four 7.5-minute quadrangles that cover the Turkey Creek caldera and geologic map of the caldera.

From abstract: This report is about six gas samples that were obtained from the Mississippian Leadville Limestone in the McElmo field, Colorado, and the Lisbon field, Utah. These samples were recorded to contain a high reading of carbon dioxide and the report investigates these results.

From abstract: Information in this report supplements the geologic map of the Stanford Canyon quadrangle that provides chemical data, thin sections, and hand specimens for each of the samples collected in the quadrangle.

From introduction: The investigation described herein is a part of the USGS Evolution of Sedimentary Basins Program. This report concerns the Pennsylvanian and Permian stratigraphic framework, structural development, and paleogeography of the San Juan Basin.

Proceedings of a workshop held in February 1990 called "Tertiary Stratigraphy of Highly Extended Terranes, Southern Basin and Range" at the Desert Research Center of the California State University System, Soda Springs, near Baker, California. This volume is a collection of stratigraphic data and interpretation.

From abstract: The information presented in this report supplements the geologic map of the Fife Peak quadrangle and supports ongoing investigations of the evolution of the Turkey Creek caldera.

From abstract: Information in this report supplements the geologic map of the Rustler Park quadrangle and supports ongoing investigations of the Turkey Creek caldera.

From introduction: This study examines mid-Tertiary mineralization of the area in the context of both detachment and basin-range faulting.

From abstract: At the request of the U.S. Bureau of Land Management, approximately 19,300 acres of the Black Mountains North Wilderness Study Area (AZ-020-009) and 23,310 acres of the Burns Spring Wilderness Study Area (AZ-020-010) were evaluated for mineral resources and mineral resource potential. In this report, the area studied is referred to, collectively or individually, as the 'wilderness study area' or simply 'the study area'; any reference to the Black Mountains North or Burns Spring Wilderness Study Areas refers only to that part of the wilderness study area for which a mineral survey was requested by the U.S. Bureau of Land Management. The study area is located in western Arizona, about 30 mi northwest of Kingman. There are no identified resources in the study area.

From abstract: The Wabayuma Peak Wilderness Study Area (AZ-020-037/043), for which a mineral survey was requested by the U.S. Bureau of Land Management, encompasses 40,118 acres in northwestern Arizona. Fieldwork was carried out in 1986-88 by the U.S. Bureau of Mines and the U.S. Geological Survey to appraise the identified (known) resources and assess the mineral resource potential (undiscovered) of the wilderness study area. Within the Wabayuma Peak Wilderness Study Area are 14 private parcels of land totaling 1,315 acres. The Wabayuma Peak Wilderness Study Area, including the 14 private parcels of land, is herein referred to as the "wilderness study area" or the "study area." The Boriana, Antler, and Copper World mines lie near the east boundary of the study area. The Boriana mine was a major tungsten-producing mine of the United States during World War II. The Antler and Copper World mines produced relatively small amounts of copper and zinc prior to 1970.

From abstract: At the request of the U.S. Bureau of Land Management, approximately 113,500 acres of the Warm Springs Wilderness Study Area (AZ-020-028/029) were evaluated for mineral resources and mineral resource potential. In this report, the area studied is referred to as the "wilderness study area" or "study area"; any reference to the Warm Springs Wilderness Study Area refers only to that part of the wilderness study area for which a mineral survey was requested. This study area is located in west-central Arizona. The U.S. Geological Survey and the U.S. Bureau of Mines conducted geological, geochemical, and geophysical surveys to appraise the identified mineral resources (known) and assess the mineral resource potential (undiscovered) of the study area. Fieldwork for this report was carried out largely in 1986-1989.

Purpose and scope: The purpose of this study was to develop a method for estimating the amount of subsurface return flow to the Colorado River in the Yuma area. This report presents a method that permits an approximate accounting of ground-water return flow from each side of the Colorado River in Yuma reach. The method presented in this report was developed specifically for application in the Yuma area. The validity of the assumptions inherent in the method was evaluated on the basis of the local hydrologic system. The applicability of the method to other hydrologic systems is not addressed in this report.

Purpose and scope: The purpose of this study was to develop a method for estimating the amount of subsurface return flow to the Colorado River in the Yuma area. This report presents a method that will permit an accounting of ground-water return flows from each side of the Colorado River in the Yuma reach. The estimates of return flow can be used by water-management agencies in determining return-flow credits for the States of Arizona and California.

Scope: This report summarizes part of the hydrologic data needed to determine the effects of streamflow on ground-water storage. The report includes (1) streamflow data at selected points between the water-conservation reservoirs on the Salt and Verde Rivers and the Gila River as Gillespie Dam, (2) changes in ground-water levels in 169 observation wells from February 1978 to May 1980, (3) an estimate of the streamflow losses along the Salt and Gila Rivers between Granite Reef and Gillespie Dams from March 1978 to June 1980, and (4) the infiltration rates on May, 9, 1979, for the Salt River downstream from Granite Reef Dam. Most of the hydrologic data in this report are available in computer-printout form and may be consulted at U.S. Geological Survey offices in: Federal Building, 301 West Congress Street, Tucson, and Valley Center, Suite 1880, Phoenix. Copies of the data can be obtained at private expense.

Abstract: Water shortages are expected in the Upper Colorado River Basin because of increasing water demands for various uses. Ground-water supplies can help to reduce water shortages but ground-water reservoirs have not been studied in detail. The regional aquifer systems analysis of the Upper Colorado River Basin is a study of the major ground-water resources of the region. Aquifers occur in the sedimentary rock sequences in basins and uplifted regions, in volcanic-rock regions, and in stream-valley alluvium. The project work will include collection and compilation of existing geologic, geophysical, hydrologic, and geochemical data. These data will be used to assess the hydrologic characteristics of the aquifer systems and to estimate the hydrologic effects of discharge from, or recharge to, selected aquifers.

From abstract: The part of Arizona south and east of Tucson is underlain by a wide assortment of deformed rocks, as well as by some major mineralized districts. A synthesis of the tectonic evolution of the region is offered in this report, which is based on older studies of mining districts and on more recent field studies by students and by the U.S. Geological Survey, augmented by field review and selective remapping of many key areas. Through this synthesis the rocks of the region are seen to have been deformed in response to diverse stresses, at various times, with an increasing degree of structural anisotropy of the rocks through time. Consequently, reactivated faults are common features, and segments of some of these faults record various kinds of movement, thereby providing unusual interpretive difficulties for many of the past local studies.

This report includes two maps of the same location, one describing water-level contour, well depth in which depth to water was measured, the other describing well from which water sample was collected and irrigated areas. It includes a letter from the district chief of the United States Department of the Interior to users of the geological survey hydrologic data.

Map and survey information of the the Aravaipa Valley area in Arizona, including information on well depths, irrigated areas, approximate boundaries, and arbitrary boundaries of ground-water area, as well as general hydrologic data and selected references.

Preliminary 16 x 7.5 minute map of the Paria Plateau NW quadrangle, showing geology, roads, drainage, meridians and parallels, triangulation stations, and air-photo centers and wing points.

A report about the lower San Pedro Valley in Arizona. This report shows how mapping discrete units of the valley may lead to a broadened understanding of Cenozoic history of intermontane basins in Arizona.

From introduction: "The purpose of this report is to show how mapping of discrete units of the valley fill may lead to a broadened understanding of Cenozoic history of intermontane basins in Arizona. The area described is in the vicinity of Mammoth Arizona where deep dissection has exposed a complex sequence of terrestrial deposits and related rocks."