Abstract Study of the distribution of the age-populations of detrital zircons in the Snake River system suggest that specific stream systems can be identified based on the detrital-zircon age-population signature (“barcode”) of ancient and Holocene sand deposits. Detrital zircon studies can be used on regional and local scales to determine changes in drainage patterns using both surface and subsurface data. Regional study of drainage patterns using detrital zircons found in Neogene strata of Idaho and southwest Montana suggest northeastward late Miocene to Holocene migration of the Continental Divide from the western side of the Pioneer Mountains to the current position in southwest Montana. Specifically, mixed populations of recycled Proterozoic detrital zircons that define the Wood River drainage are not found in the western Snake River Plain until after 7 Ma. Late Miocene eastward drainage from the central Snake River Plain to southwest Montana is suggested by 9–12 Ma detrital zircons found in fluvial strata less than 6 million years old, of the Sixmile Creek Formation Basalt eruptions of the Eastern Snake River Plain during the Pliocene and Pleistocene also caused drainage diversion. Detrital zircons in Pliocene sands from coreholes at Wendell and Mountain Home Air Force Base contain Big Lost River zircon provenance, suggesting that during the Pliocene, the Big Lost River flowed west along the central Snake River Plain. Late Pliocene and early Pleistocene basaltic volcanoes and rhyolite dome eruptions resulted in volcanic highlands, the Axial Volcanic Zone of the eastern Snake River Plain and the northwest-trending Arco Volcanic Rift Zone (which includes Craters of the Moon volcanic center). The development of these volcanic highlands disrupted the ancestral drainage of the Pliocene Big Lost River system, confining it to the Big Lost Trough, a volcanically dammed basin of internal drainage on the Idaho National Laboratory. After the Big Lost Trough was cut off from the main Snake River, basalt eruptions, local subsidence, and climate controlled the courses of the rivers that flowed into it. Detrital-zircon populations in core samples reveal the provenance of specific sand beds from the Big or Little Lost River systems.

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 D 1 and D 2 indicates that shear occurred along planes approximately parallel to bedding such that strata moved to the northwest (D 1 ) and the northeast (D 2 ) 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.