Geologic Map of the Bartlett Dam Quadrangle and Southern Part of the Horseshoe Dam Quadrangle, Maricopa County, Arizona v. 2.0

This map and report summarize the geology of the northern part of the lower Verde River Valley in central Arizona. The map encompasses the Bartlett Dam 7.5' U.S.G.S. topographic quadrangle and the southern part of the Horseshoe Dam 7.5' US.G.S. topographic quadrangles (see Figure 1). The study area is on the northeast fringe of the Phoenix metropolitan area due east of Cave Creek and approximately 50 kilometers northeast of downtown Phoenix. The eastern side the study area includes Bartlett Dam, the western two-thirds of Bartlett Reservoir, and part of the Verde River. The center of the study area includes the volcanic hills of Brushy Mountain and overlying dissected basin-fill deposits. Late Tertiary basin-fill stratigraphy is well-exposed in the southeastern corner of the map. Most of the northern part of the study area is underlain by coarse-grained K-feldspar porphyritic granite which has been eroded into a well-developed pediment south of the drainage divide (see Figure 2). This report is part of a digital republication of a 1996 geologic map originally created by the Arizona Geological Survey with financial support from the STATEMAP Program Contract #1434-95-A-1353. Preparation for republication was conducted by students from the University of Arizona with financial support from the U.S. Geological Survey, National Geological and Geophysical Data Preservation Program (G22AP00222) and included the production of a new GIS geodatabase and a revised map layout. The following text report has not been altered and remains identical to the 1996 original, but there may be situations where unit names, ages, symbology, or other geologic information contained within this report do not match the information presented in the new map layout or GIS geodatabase.