The geologic map (at a scale of 1:24,000 or two inches equals 2000 feet), covering an area of approximately 35 sq km between the Willow Springs Ranch on the south and Star Flat on the north, is a revision and update of Krieger (1974a, 1974b), who showed only the northern fringe of the study area, and Dickinson (1987, 1992), who depicted the geologic relations at smaller scale (1,62,500 and 1:125,000, respectively). Access to the study area is provided by Willow Springs Road, which turns north off the paved highway between Oracle and Oracle Junction. The regional geologic context ofthe Star Flat-Willow Springs area is discussed by Dickinson (1991).