The Canelo Hills are underlain by northwest strikingfolded and faultedPermiansedimentary rocks and Jurassic–Triassicvolcanic rocks. The southwest margin extending toward the Patagonias is underlain by Cretaceous–Eocene volcanics.[1] The southern end of the Canelo Hills contain evidence for a volcanic caldera, the Parker Canyon Caldera. This caldera is mapped as a kidney shaped feature stretching from just north of Canelo Pass some 15 miles (24 km) to the southeast into the Huachucas and underlying the eastern portion of the San Rafael Valley.[2] The Jurassic volcanics in the area consist of rhyolite welded tuff containing large exotic blocks of limestone, quartzite and other rock types interpreted as "intercaldera megabreccia lenses".[2]
^ abHouser, B. B., et al., Historic Mining Camps of Southeastern Arizona: a Road Log with Geologic and Historic Highlights, in USGS Researches on Mineral Resources – 1994 Part B Guidebook for Field Trips, U.S. Geological Survey Circular 1103–B p. 26 (map) & pp. 46–47