The geologic map and accompanyinq text that compose Bulletin 195 represent an important contribution to our understandinq of the geologic framework of Arizona. The South Mountains are among the recently recognized "metamorphic core complexes" of western North America and, as such, are similar in age and origin to other core complexes in Arizona, including the Rawhide, Buckskin, Harquahala, Harcuvar, White Tank, Picacho, Tortolita, Santa Catalina, and Rincon Mountains. The accessibility and comparative geoloqic simplicity of the South Mountains make them an ideal area in which to study the characteristics and origin of these important complexes.
Prior to Dr. Reynolds' work in the area, geologists believed that the South Mountains were largely composed of 1.6- to 1.7-b.y.-old Precambrian gneiss. Dr. Reynolds, however, has demonstrated that the entire eastern half of the range is actually composed of sheared granitic rocks that are only 25 m.y. in age. He has also discovered a major, previously unrecognized, low-angle detachment fault that projects into the subsurface beneath Phoenix, Tempe and Mesa.
Reynolds, S.J., 1985, Geology of the South Mountains, Central Arizona. Arizona Geological Survey Bulletin-195, 75 p., 1 map plate, scale 1:24,000. (http://repository.azgs.az.gov/uri_gin/azgs/dlio/1655)
