MULTIPLE GENERATIONS OF CENOZOIC NORMAL FAULTS AND RELATED TILTING IN THE GOSHUTE MOUNTAINS AND TOANO RANGE, ELKO COUNTY, NEVADA, WITH GEOLOGIC IMPLICATIONS

The Goshute Mountains and Toano Range are located in easternmost Elko County, which contains Paleozoic carbonate-clastic strata in several structural plates bound by Mesozoic reverse faults. In the southern extent of the study area near White Horse Pass, Cenozoic rocks and underlying Paleozoic strata dip 65-90°W, mainly due to extensional dismemberment and tilting by multiple generations of initially east-dipping normal faults. Farther north in the Spring Gulch area, Cenozoic rocks have been tilted ~30°W along two generations of normal faults. Southwest of Silver Zone Pass, basal Cenozoic rocks and underlying Paleozoic strata dip ~60°E. Dips of Cenozoic rocks decrease up section to ~20°E, constituting a half graben in the hanging wall of a west-dipping low-angle normal fault system that was active ~15 Ma. In the northern Toano Range northwest of the Toano Springs pluton, Cenozoic rocks dip ~5-40°E, whereas Paleozoic strata dip ~40-60°E due to at least two generations of normal faults, of which at least one was active before ~13 Ma. Thus the dip polarity of Cenozoic rocks changes along strike from west-dipping strata dismembered mostly by east-dipping faults in the south to east-dipping strata dismembered by west-dipping faults to the north, suggesting the presence of a tilt domain boundary near Morris Basin.

Restoration of Cenozoic structural deformation has implications for understanding the distribution, style, and original geometry of Mesozoic shortening, magmatism, and mineral deposits in the region. Reverse faults in the in the northern Toano Range are nearly flat and would restore to ~40°W. The original orientations of plutons and associated hydrothermal systems in the range vary widely. The Jurassic White Horse pluton plunges moderately to shallowly to the east; the Jurassic Spring Gulch stock plunges moderately to the east; and the Jurassic Silver Zone Pass, Cretaceous Toano Springs, and Eocene Castle Park plutons in the northern Toano Range plunge moderately to the west.