Named for Salero Ranch and Mine in Santa Rita Mountains, Mount Wrightson quad, Santa Cruz Co, AZ. The ranch and mine are the type area. Crops out in southwest and north end, Santa Rita Mountains. Contains a lower member of dacitic flows and tuff breccia, an exotic block member that contains large blocks (some as much as 1,000 ft long) of Jurassic and older rocks in a volcanic flow breccia, a rhyodacitic welded tuff member, an arkose member of arkosic fanglomerate, conglomerate, sandstone, and tuff, and an upper member of mixed volcanic and sedimentary rocks--tuffaceous sandstone, tuff breccia, agglomerate, conglomerate, quartzite. Biotite from welded tuff member has K-Ar age of 72.5 +/-2.2 Ma. The formation has a composite maximum thickness of about 5,000 ft. Conformably overlies the Fort Crittenden Formation, or on Squaw Gulch Granite. Is intruded by plutons of latest Cretaceous age. Is assigned to the Late Cretaceous. Biotite from welded tuff has 72.5 +/-2.2 m.y. K-Ar method.
[NOTE: The Department of the Interior's Secretarial Order 3404, issued on November 19, 2021, formally identifies the term “squaw” as derogatory. That Order will create a federal Derogatory Geographic Names Task Force, to find replacement names for geographic features in use by federal agencies. We’re awaiting guidance from the Task Force, and will then take the appropriate actions.]

Source: GNU records (USGS DDS-6; Denver GNULEX).

Is youngest Cretaceous formation in Santa Rita Mountains (Santa Cruz and Pima Cos, AZ) and Empire Mountains (Pima Co, AZ) in Basin-and-Range province. No Upper Cretaceous rocks recognized in Whetstone Mountains. Overlies Fort Crittenden Formation (Campanian) conformably locally on west side of Santa Rita Mountains; elsewhere in range, conformably overlies Jurassic granite. Overlies rocks of Bisbee Group (Lower Cretaceous) unconformably in Empire Mountains. Is intruded by rocks dated as very Late Cretaceous; is overlain by a variety of rocks assigned to Tertiary or Quaternary. Is as much as 5,000 ft thick in Santa Rita and Empire Mountains. Lower part is considered at least approximately correlative with numerous andesitic rocks in region (see fig. 5). Rhyolitic tuffs of Salero are considered correlative with numerous rhyolitic tuffs in region (fig. 5). Units comparable to upper part of Salero in Santa Rita Mountains have not been identified elsewhere in region. Radiometric dating (Gill and Cobban, 1966) and stratigraphic position dating indicates probable late Campanian and possibly earliest Maestrichtian age.

Source: GNU records (USGS DDS-6; Denver GNULEX).