Exhuming the Remains of the Inactive Mountain-Front Pirate Fault, Santa Catalina Mountains, Southeastern Arizona

The ~25 km accessible trace of the north-south trending, west-side down, normal, mountain-front Pirate fault has been mapped to locate and describe those erosionally exhumed remnants of the fault that together provide a basis for structural reconstruction of this nominally Basin-Range tectonic feature. The fault forms the western boundary of the Santa Catalina Mountains in southeastern Arizona, where it separates the uplifted Santa Catalina structural block on the east from the down-dropped, alluvial Cañada del Oro basin on the west. Vertical displacement on the fault is estimated to be ~4 km, accumulated over a ~6 my active duration from ~12 to ~6 Ma. Following cessation of active uplift, the fault was buried under detritus eroded from the uplifted Santa Catalina block and, currently, is being exhumed by the downcutting Cañada del Oro and its tributaries. This field examination reveals the fault to have left a sparse but diverse collection of remains implying a varied history of fault development and evolution.