Antler orogeny Antler orogeny in detail and somewhat refined its age span: "During the Antler orogeny, formations in Battle Mountain ranging in age from Ordovician to Mississippian (?) were complexly folded and faulted. As these rocks are unconformably overlain by the Battle Formation of Early Pennsylvanian (Des Moines) age, the orogeny probably took place during the Late Mississippian. The orogeny may have continued into Early Pennsylvanian, however, for the coarse conglomerates of the Battle Formation indicate derivation from a rugged highland area." In a subsequent influential paper, Roberts and others adjusted the age of the Antler orogeny as follows: "This belt is
Sonoma orogeny arcs, composed of volcanic and volcaniclastic strata and paired geotectonically with Sonoma accretionary prisms to the east, are present in the Klamath-Sierran region of the Cordilleran orogen to the south of volcanic cover in the Pacific Northwest. Burchfiel and Davis presented a detailed model relating the Sonoma orogeny to convergent plate tectonic processes. They postulated an east-dipping subduction zone beneath a magmatic arc to the west of the continent. In this scheme, a back-arc basin floored by oceanic crust lay between the arc and the continent. The Sonoma orogeny involved closure of this basin and a process by which the