Thimble Peak in Pusch Ridge Wilderness - Tucson
Geology and History

• Rocks​ that make up Thimble Peak are of the Thimble Peak sill, part of the Wilderness Suite sills that are intrusions of peraluminous granite (high proportion of aluminum oxide), with abundant muscovite.  Wilderness Suite sills are 46-57 million years old.  They are light-colored muscovite granite that represent the youngest phase of voluminous magmatism (igneous intrusions) during the Laramide mountain-building phase in Arizona.  Thimble Peak sill, along with other sills in the Santa Catalina Mountains, was injected into 1.4 billion year old Oracle granite.  Thimble Peak is the erosional remnant of this sill, which was uplifted after it cooled.
• Sabino Creek follows the deep cut of the Sabino Canyon Fault in metamorphic core complex rocks of Mylonitic Oracle Granite (gneiss) and Mylonitic Wilderness Suite Granite.
• Gordon Hirabayashi, an Auburn, Washington native defied U.S. government orders in 1942 by Franklin D. Roosevelt that were to evacuate and place into internment camps U.S. West Coast Japanese Americans during WWII.  He was imprisoned for 90 days - his Supreme Court case was the first to challenge the government's curfew and expulsion of Japanese Americans.  Link:  Gordon Hirabayashi, by David Takami.