Pennsylvanian Paleogeography, Southwestern US
Pennsylvanian Paleogeography, Southwestern US (310 Ma). Huge changes in paleotectonics from earlier periods affected western North America. The Ancestral Rockies rose across the southern Western Interior. The Antler Mountains were already being worn down by erosion and even began subsiding in some areas. A marine basin covered most of western Utah and eastern Nevada.
View to west of above. In this interpretation, the Stikine fragment of the southern McCloud arc migrated westward while the Quesnell fragment of the Northern McCloud arc remained near western North America. The transform fault between the two may have been the same transform that truncated SW North America during the Late Pennsylvanian and Permian. Follow this interpretation and watch for a contrasting one in the Permian and Mesozoic