The Bouse Hills are located in west-central Arizona (Fig. 1) and are within the Basin and Range physiographic province of the Southwest. The Bouse Hills consist of four rock assemblages (Fig. 2), as follows: (1) Proterozoic crystalline rocks, (2) moderately to steeply tilted Oligocene(?) to lower Miocene volcanic and sedimentary rocks, (3) a Miocene pluton and related dikes, and (4) flat-lying to gently tilted Miocene volcanic and minor sedimentary rocks. Assemblages (1) and (2) were tilted by early Miocene rotational normal faulting that was widespread in the Basin and Range province (Spencer and Reynolds, 1989). In the Bouse Hills, tilting was probably related to movement on the Plomosa detachment fault which projects beneath the Bouse Hills from the west (Scarborough and Meader, 1989). Manganese and barite mineral deposits are mineralogically distinct, and fluid-inclusion data indicate that they were derived from aqueous fluids with different salinities. These deposits are confined to the Miocene volcanic and sedimentary rocks. This report includes a geologic map of the Bouse Hills at a scale of 1:24,000 (plate 1), descriptions of rock units (Appendix 1), and a stratigraphic correlation diagram (Fig. 3). Also included are descriptions of mineral deposits (Appendix 2) and a geologic map of some small hills northwest of the Bouse Hills (Fig. 4). ( 21 pages)

These nine maps depict the general ages and distribution of Quaternary geomorphic surfaces and associated alluvium of the northern Avra Valley-Desert Peak (AVDP) area, Pinal and Pima counties, southern Arizona. The area mapped includes portions of the piedmonts surrounding the Silver Bell, Picacho, and Tortolita mountains, and the basin flats between them. The southern margin of the study area is approximately 40 km northwest of downtown Tucson. The AVDP area is one of many broad valleys in the Basin and Range physiographic province of southern Arizona. The Basin and Range province in the vicinity of the study area is characterized by relatively small mountain ranges with fairly low relief separated by wide, gently sloping piedmonts and basin bottom river drainages. The major drainages flowing through study area are the Santa Cruz River, Brawley Wash, and McClellan Wash. By indicating the age and physical characteristics of surficial alluvial deposits, these maps provide a basis for evaluating the Quaternary geologic history of the area and assessing potential geologic hazards. Alluvial deposits differentiated for these maps are assigned to Quaternary and Upper Tertiary age categories primarily on the basis of the estimated age of cessation of major deposition on geomorphic surfaces associated with the deposits. Relative topographic positions of each surface, drainage patterns, surface characteristics, and degree of soil development associated with the surface are the principal criteria used to assess surface age. Six ages of surfaces are differentiated in these maps. Map units are further subdivided into piedmont and basin axis units. The characteristics of each map unit are described below. The estimated ages of the units are inferred by correlation with similar surfaces and soils dated elsewhere in the southwestern United States (Gile and others, 1981; Bull, 1991; Menges and McFadden, 1981). Generalized lithologies of exposed bedrock are also depicted on the maps. (11 pages)

This map depicts the distribution of geomorphic surfaces and associated alluvium of the southern and southwestern piedmont of the Tortolita Mountains in Pima County, northwest of Tucson, Arizona. The Tortolita piedmont is located on the northwestern fringe of the Tucson metropolitan area. Much of the eastern portion of the piedmont already has some development, and the rest of the piedmont likely will be developed in the next few decades. Delineating surficial alluvial deposits by age and physical characteristics provides a basis for assessing the character and distribution of potential geologic hazards and evaluating the Quaternary geologic history of the area. Detailed surficial geologic map of the southern Piedmont of the Tortolita Mountains, Pima County, southern Arizona; report and map, map scale 1:24,000.

One of the fastest growing areas of Arizona is the eastern part of the Phoenix Basin near the communities of Chandler, Gilbert, Mesa, and Apache Junction. Much of this development has occurred on the piedmont near the base of the mountains where little of the surficial geology has ever been mapped. Because this area of the Phoenix Basin will continue to grow in the future, there is a need to understand the nature and distribution of surficial deposits. Surficial geologic mapping provides a spatial data base for assessing potential geologic hazards (pearthree, 1991), for defining important groundwater recharge zones, and for analyzing the physical characteristics of surface deposits for excavation purposes. Such mapping is also valuable to earth scientists who are interested in defining the links between landscape evolution and climate change (Bull, 1991). This report presents the results of surficial geologic mapping in the eastern margins of the Phoenix Basin including the Superstition Mountain piedmont and Queen Creek alluvial fan (Figure 1). The region mapped is contained within the Florence Junction, Florence NE, Goldfield, Magma, and Superstition Mountains SW quadrangles (1:24,000), and part of the Weavers Needle quadrangle (1:24,000). This area contains a variety of landscape elements including steep mountain slopes, pediments, and alluvial fans. Included within this report is a discussion of the origins of pediments and an analysis of streamflow processes on the Queen Creek fan. ( 33 pages; 6 map sheets, map scale 1:24,000)

This report contains four detailed maps depicting the distribution of Quaternary alluvial deposits and their associated geomorphic surfaces in the northern portion of the Verde Valley. Preliminary age estimations based on relative age criteria and soil development characteristics are assigned to each unit. Each map also depicts the distribution of generalized bedrock types in the area. Geologic structures in the bedrock units other than the principal trace of the Verde Fault are not included in these maps. Each map in this report contains a wealth of geological information concerning the effects of Quaternary climatic fluctuations on the evolution of the Verde River, its major tributaries, and adjacent piedmont areas. Evident in these maps is the strong influence of drainage basin and substrate lithology on the evolution of the regional landscape and the persistence of landforms. In addition, the maps contain information relevant to the distribution and character of flood hazards, vegetation assemblages, and potential soil problems. (20 pages; 4 map sheets, map scale 1:24,000)

This report and accompanying maps describe the surficial geology, geomorphology, and geologic hazards of the northern Tucson metropolitan area. The mapping covers the Tucson North and Sabino Canyon 7 1/2’ quadrangles and includes portions of the City of Tucson and unincorporated Pima County (Figure 1). The map area encompasses the northern part of the basin floor, the southern flank of the Santa Catalina Mountains, and the dissected piedmont between them known as the Catalina foothills. Basin floor areas have been thoroughly altered by urban development, and the Catalina foothills have undergone substantial development during the past 30 years or so. The mountains generally are within the Coronado National Forest and are not developed, but some homes have been built on the lower flanks of the mountains up to the forest boundary. This report is intended to enhance our understanding of the recent geologic development of the northern Tucson metropolitan area and to aid in assessing and understanding geologic hazards in this area. This surficial geologic mapping is part of continuing efforts by the AZGS to map the geology of the Phoenix – Tucson urban corridor, and it complements previous mapping efforts in the Tucson area (McKittrick, 1988; Jackson, 1989; Demsey and others, 1993; Field and Pearthree, 1993). We have incorporated recent mapping and description of the geologic framework of the Catalina foothills (Dickinson, 1999) into this map. The report is organized into a brief introduction and explanation of mapping methods, unit descriptions, a summary of the geologic and geomorphic framework of the area, and a discussion of geologic hazards. (28 pages)

Management of flood hazards on piedmonts of the western United States is increasingly important as urban development expands into these areas. In the western United States, the term “piedmont” describes the low-relief, gently sloping plains between mountain ranges and the streams or playas that occupy the lowest portions of the valleys. Distributary, downstream- branching fluvial systems are common in piedmont areas, and all or parts of many of these distributary systems are active alluvial fans. Management of flood hazards on active alluvial fans is particularly challenging because of complex flow patterns, widespread inundation, local high-velocity flow, and the potential for development of new channels during floods. Geologic and geomorphologic analyses provide insights into the fluvial processes on piedmonts and thus can be invaluable in assessing flood hazards (Pearthree, 1989; Baker and others, 1990; Field and Pearthree, 1991; Hjalmarson and Kemna, 1991; Pearthree and others, 1992; Hjalmarson, 1994; Field, 1994a; 1994b; National Research Council, 1996; Field and Pearthree, 1997; Pearthree and others, in press). This field guide provides an overview of investigations of the Tiger Wash distributary drainage system in western Arizona, which experienced an extreme flood in late September, 1997. (34 pages)

This report and maps describe the geology, geomorphology, and geologic hazards in the Three Points quadrangle, on the southwestern fringe of the Tucson metropolitan area in unincorporated Pima County (Figure 1). The map area is located in the transition between the upland, moderately dissected Altar Valley to the south and the broad, undissected basin called Avra Valley to the north. The community of Three Points (also called Robles Junction) lies on the approximate boundary between these two geographic areas. The map includes a nine-mile-long reach of Brawley Wash, which cuts through the map area from southwest to northeast. Brawley Wash heads just south of the U.S. – Mexico border and drains all of Altar and Avra valleys before joining the Santa Cruz River northwest of Tucson. About 60 percent of the Three Points quadrangle consists of the northwestern piedmont of the Sierrita Mountains. The quadrangle also includes a small part of the northwestern piedmont of the Coyote Mountains and the southern fringe of the Roskruge Mountains. The quadrangle is generally undeveloped, and is currently used primarily for grazing. Some low-density suburban development has occurred around the community of Three Points and on the Sierrita and piedmont to the south. Much of the floodplain and terraces of Brawley Wash has been developed for agriculture. The Three Points quadrangle will likely experience much more urban/suburban development in the next few decades. This map and report may be of use in avoiding or mitigating geologic hazards in this area. (21 pages)

This report summarizes the geology and geomorphology of 12 small watersheds in the Peloncillo Mountains, southwestern New Mexico. The study site is located in the central portion of the Malpai Borderlands project area, on the eastern piedmont of the southern Peloncillo Mountains (Figure 1). It consists of an eastward trending ridge with small dissected basins on either side, and is bordered on the north and south by Walnut and Whitmire creeks, respectively. These creeks flow eastward into southern Animas Valley. The U. S. Forest Service has selected 12 watersheds along the ridge (Figure 2) for a paired watershed experiment to compare effects of two burning seasons, spring and summer, on native vegetation, wildlife, surface water flow, slope stability and erosion (G. Gottfried, US Forest Service, pers. comm., October 2000). As part of this experiment, the Forest Service is installing a sediment trap and two different-sized flumes on each study watershed to record and compare sedimentation and surface flows before and after burning. One flume will be located about 50 feet downstream from the sediment trap and will record higher volume flows of up to 57 cubic feet per second (cfs). Another flume will be located 18 feet further downstream and will record lower volume flows of up to 4 cfs (G. Gottfried, US Forest Service, pers. comm., October 2000). A major concern with this study area is that local geology may provide pathways for surface water to infiltrate and flow between study watersheds, causing erroneous runoff results, or to circumnavigate the flumes altogether. Another concern is a potential increase in erosion rates, or decrease of slope stability, after burning. The purpose of this report is to describe the geologic and geomorphic framework of the study area, to delineate surficial deposits to help define potential erosion, and to provide information concerning potential for sub-surface flow between watersheds or under the flumes. Field investigations and mapping were done in November, 2000, and January, 2001. A 1:12,000-scale map showing bedrock and surficial geology is included with this report.