Socorro, NM: New Mexico Bureau of Mines and Mineral Resources, 1975. Third Edition. Soft cover. 8vo (22 x 14 cm). 116 pp. Glossy green covers with illustration of horses and their riders in mountains to upper. Green titles to upper and spine. Text block tight and unmarked. Large fold-out map..... More about Trail Guide to Geology of the Upper Pecos; Trips to the Geologic Past