Description:
The rocks and structures exposed in the Moon Mountains of the Colorado River
Indian Reservation, west-central Arizona, record Mesozoic thrusting within the Maria
fold and thrust belt, and superimposed Tertiary detachment faulting related to the regional
Whipple-Buckskin-Rawhide detachment system. The major structures of the Moon
Mountains are (1) the Valenzuela thrust fault, (2) the Moon Mountain detachment fault,
and (3) the Copper Peak detachment fault. Lithologies consist primarily of Mesozoic and
Tertiary intrusive rocks and crystalline gneisses of Precambrian age, with minor but
important exposures of deformed and metamorphosed sedimentary and volcanic rocks. A
newly-described section of metamorphosed, lower Mesozoic sedimentary rocks, the
Valenzuela metasedimentary section, is assigned to the Buckskin Formation (Reynolds et
al., 1987) of western Arizona.