The stratigraphy and structure of the Waterman Mountains, Pima County, Arizona

Abstract

The Waterman Mountains are located about 35 miles west of Tucson in Pima County, Arizona. In the Central and Eastern portion of the range the Pinal schist and Apache group are missing and a pre- Cambrian (?) granite underlies the Paleozoic sediments. The stratigraphy in the mountains includes the Cambrian Troy quartzite and Abrigo formation, the Devonian Martin formation, the Mississippian Escabrosa limestone, the Pennsylvanian Horquilla formation, the Pennsylvanian-Permian Andrada formation, the Permian Scherrer, Concha, and Rainvalley formations, and Cretaceous (?) strata. The sediments were deposited in a shallow, fairly stable basin. The Watermans were probably uplifted during the Laramide orogeny, when compressive stresses from the southwest pushed wedges of Paleozoic strata through the overlying Cretaceous (?) beds. The trends of the major faults within the mountains support the southwestern origin of compression with relatively older faults trending N. 450 W. and dipping southwestward. Relatively younger faults, probably tensional, trend N. 60° 70° E. and N. 85° W. Later Tertiary igneous intrusions are represented by rhyolite sills and dikes in the Cretaceous (?) sediments north of the range. The mineralization in the Watermans is probably related to the Tertiary igneous activity.