Character and Regional Significance of Great Falls Tectonic Zone, East-Central Idaho and West-Central Montana

Sequence Stratigraphic Framework of the Late Devonian (Frasnian) Duperow Formation in Western and Central Montana

“…This orogeny is thought to have produced foreland flexures inboard of the continental margin on the platform in Montana and may be responsible for various structural features, such as the Central Montana Trough and Central Montana Uplift, through reactivation of basement faults and zones of weakness (O'Neill & Lopez, 1985;Dorobek et al, 1991;Giles & Dickinson, 1995).…”

“…These strata thin to near zero from the Williston Basin into eastern and north-central Montana and thicken to 200 feet in west-central Montana and up to 800 feet in northwest Montana (Sandberg & Hammond, 1958). & Lopez, 1985;Nelson, 1995). Basement features include the Great Falls Tectonic Zone, Pendroy Fault Zone, Lewis and Clark Line, Scapegoat-Bannatyne Lineament, Wyoming Craton, Medicine Hat Block, Belt Basin, and Montana Aulacogen (Figure 10).…”

“…Previous work suggests that the Wyoming Craton (Archean) developed during extensive magmatism 2.5-2.9 Ga and extruded surrounding crust, melting it, and diverting it away from the craton and its mantle root (Mueller & Frost, 2006). This melt of felsic crust was determined to have migrated to weaker crustal zones, such as the Great Falls Tectonic Zone, where it produced mineral deposits and magmatism within Cretaceous rocks (O'Neill & Lopez, 1985;Foster et al, 2006).…”