Southwest Montana

Map exercises in southwest Montana sample several geologic provinces including the Fold-thrust belt and Helena salient, northern Laramide, and northern Basin and Range. Metamorphic rocks in the basement include Archean rocks of the Wyoming craton and Paleoproterozoic rocks wihtin the Great Falls Tectonic Zone. Sedimentary strata range through all geologic Eras from the ~1.4 Ga Proterozoic Belt Supergroup, through Paleozoic marine rocks, Mesozoic continental and marines rocks to Cenozoic volcanic rocks and basin fill.