David M. Miller, 1980. "Structural geology of the northern Albion Mountains, south-central Idaho", Cordilleran Metamorphic Core Complexes, Max D. Crittenden, Jr., Peter J. Coney, George H. Davis
Download citation file:
The northernmost of a chain of four or five domes in the Albion Mountains was studied in order to understand its origin and deformational history. The dome is part of a metamorphic terrane that is composed of Precambrian W basement gneiss that is overlain by a Precambrian(?) and Paleozoic metasedimentary rock succession that was metamorphosed to the amphibolite facies in the Albion Mountains.
Four phases of ductile deformation are recognized in minor structures. The first two phases of deformation followed extensive low-angle faulting of younger-on-older type and resulted in the formation of overturned and flattened folds in the weaker rock units and penetrative lineations and foliations in the thick quartzite units. Vergence of minorfolds that formed during D1 and D2 indicates that shear occurred along planes approximately parallel to bedding such that strata moved to the northwest (D1) and the northeast (D2) relative to the basement. Third-phase deformation locally created overturned folds and small bedding-plane faults with geometries that indicate that higher strata moved outward from the apex of the present dome relative to the underlying strata, which suggests that these structures formed during the rise of the dome. The fourth phase of deformation is typified by kink folds whose axes trend N15° E and are horizontal. Movement on a low-angle fault that separates Pennsylvanian sedimentary rocks from underlying metamorphic rocks followed the second phase of deformation and may have been concurrent with late ductile deformation in the more deeply buried rocks.
Timing of the metamorphism and intense deformation in the Albion Mountains is elusive, but it apparently occurred between Late Triassic and Early or middle Cretaceous times; numerous Tertiary K-Ar and Rb-Sr ages from metamorphic rocks indicate that less intense deformation and moderate temperatures continued in the more deeply buried rocks until the Miocene.
The structural history of the Albion metamorphic terrane is thus interpreted as an early to middle Mesozoic period of extensive younger-on-older faulting and ductile shearing on nearly horizontal planes over a little-deformed basement, and a late Mesozoic to early Cenozoic period of less intense deformation and metamorphism. This history is similar to that of other metamorphic terranes in the Great Basin.