Land of Cochise (Southeastern Arizona)

About this guidebook

We finally made it! If my memory serves me correctly, the idea for this field conference was born out of a casual conversation with Wes Peirce of the Arizona Bureau of Geology in the fall of 1969 at the Sierra de Samalayuca stop in Mexico. This is our third cooperative arrangement with the Arizona Geological Society, having shared excellent trips to Black Mesa Basin (1958, Guidebook 9) and the Mogollon Rim Region (1962, Guidebook 13). The first day road log is from Lordsburg to Douglas via Granite Gap and San Bernadino Valley with an extension to the southern end of the Mule Mountains. This route in southwestern New Mexico and southeastern Arizona traverses basins containing Pleistocene playas and Plio-Pleistocene valley fill and volcanics, and intervening ranges of pre-Pliocene rocks.The second day road log is from Douglas to Tucson via Bisbee, Tombstone, Charleston, Fort Huachuca and Sonoita. The route traverses Paleozoic and Mesozoic strata, copper and silver ore deposits, complicated Mesozoic and Cenozoic structural deformation and accompanying plutonism and volcanism, all of which contribute significantly to the geologic history of the Basin and Range province in southeastern Arizona. The third day road log is from Tucson to Colossal Cave and Saguaro National Monument. The focus of this trip is to examine the physical and geometric relations among rocks and structure in the outer margin of a so called “metamorphic core complex”. Specifically we will observe cataclastically deformed gneisses and folded mylonitic schists in the augen gneisses core, and shattered unfoliated Precambrian granite and Paleozoic sedimentary rocks resting atop the decollement zone.