geothermal resource potential of the safford-san simon basin, arizona

attitudes of the thrust faults, reverse faults, and Paleozoic rocks are beo
0
tween 0 and 35. This means that lower Paleozoic rocks may be preserved
beneath Tertiary volcanic rocks and sediment in the southern Safford-San
Simon Basin in the vicinity of Interstate 10.
Basin and Range
Mid-Tertiary volcanism probably ceased in the Safford-San Simon area by
19 m.y. because the youngest observed volcanism in the area occurred in the
northern Peloncillo Mountains 20 m.y. ago.
Twenty-million-year-old felsic
lavas and tuffs are observed in Tollgate Canyon and the Gila Box area (Don
Richter, pers. comm.). Post 20 m.y. and contemporaneous with the mid-Tertiary
volcanism, coarse clastic rocks were deposited in topographically low areas.
Sediments of this depositional period are observed in the Gila Box at the
mouth of Bonita Creek and in Eagle Creek Canyon near Clifton. Heindl (1958)
named these sediments the Bonita Beds and Gold Gulch Beds, respectively; and
both have basaltic andesite flows and silicic tuffs in basal exposures along
canyons.
In the Tucson area, the Rillito beds are believed to represent
another similar Miocene conglomerate deposit (Pashley, 1966).
The Rillito
beds are tilted and faulted by normal listric faults and overlie the Catalina
fault, the low-angle decollement zone of the Catalina "metamorphic core complex".
Unexposed tilted and faulted Miocene gravels may comprise the basement
in the Safford-San Simon basin adjacent to the Pinaleno Mountains and
may overlie an inferred decollement zone associated with the Pinaleno Mountains
"metamorphic core complex".
The tilted Miocene sediments immediately
pre-date Basin and Range faulting.
Present-day basins and ranges began to develop during middle to late
Miocene (15 m.y. to 10 m.y.) $carborough and Peirce, 1978). Scarborough and
Peirce (1978) name this tectonism the "Basin and Range disturbance".
The
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