The Pirate Fault of the western Santa Catalina Mountains, Tucson, Arizona: The Movie

Not so long ago, mountain building was alive and well in southern Arizona. A new Arizona Geological Survey Contributed Report by Dwight Hoxie, Exhuming the Remains of the Inactive Mountain-Front Pirate Fault, Santa Catalina Mountains, Southeastern Arizona, describes the Pirate fault system of the western Santa Catalina Mountains. The fault demarcates uplift of the Santa Catalina structural block to the east, from the down-dropped, alluvial Cañada del Oro basin to the west. Vertical displacement on the nearly 16 mile long fault is about ~ 2.5 miles or 13,200 feet, which occurred over a six million year span from ~ 12 to 6 million years before the present. 

This short, 2-minute video presents Dwight Hoxie (USGS retired) describing basalt dikes that intrude the fault zone. The dikes appear undisturbed by faulting suggesting a post-fault emplacement age of less than 5 Ma.

Citation for the full report,  Hoxie, D.T., 2012, Exhuming the Remains of the Inactive Mountain-Front Pirate Fault, Santa Catalina Mountains, Southeastern Arizona. Arizona Geological Survey Contributed Report CR-12-F, 18 p.