“…The Ruby Range block uplift was mapped and described by Tysdal (1970Tysdal ( , 1976a, who concluded that uplift of the range and folding of the sedimentary rocks was a result of differential vertical movements of discrete basement blocks (Tysdal, 1970, p. 105-119). Swanson (1970, p. 670, 718-719) interpreted most of the steep faults of southwest Montana as reverse faults reflecting vertical movements along ancient shear zones, and he attributed much of the folding in this region to draping over uplifted, fault-bounded, rigid basement blocks of Archean crystalline rocks.…”