The study area is located ~40 km southeast of downtown Tucson, and is bounded by the Rincon Mountains on the north, the Empire Mountains on the southeast, and the northernmost Santa Rita Mountains on the southeast. The map area covers the southern part of the Vail 7 ½' Quadrangle, including all the Paleozoic rocks in the Colossal Cave area. Field mapping was completed during October 2000 through April 2001 as part of a multiyear mapping program directed at producing complete geologic map coverage for the Phoenix-Tucson metropolitan corridor. A 1:24,000 scale map is the primary product of this study (Plate 1). This map consists almost entirely of new mapping but locally incorporates data from published mapping by other workers. The accompanying report describes rock units and other geologic features. This mapping was done under the joint State-Federal STATEMAP program, as specified in the National Geologic Mapping Act of 1992. Mapping was jointly funded by the Arizona Geological Survey and the U.S. Geological Survey under STATEMAP Program Contract #00HQAG0149.