Triassic Paleogeography, Southwestern US
Early Triassic Paleogeography, Southwestern US (240 Ma). A broad fluvial and shallow marine depositional system (the Moenkopi Formation) covers much of the southern Western Interior. To the west, the Stikine and Quesnell elements of the McCloud arc collide and in turn collapse the Havallah back arc basin as the Sonoman orogeny continues. The Cache Creek forearc complex is trapped between the two arc elements
View to west of above. Oceanic plateau fragments continue to acrete to western North America and the ocean plate subducts below the continent. As subduction continued, the Cordilleran arc became established
Late Triassic Paleogeography, Southwestern US (215 Ma). The Chinle fluvial system covered much of the Western Interior. Chinle rivers were sourced in remnant highlands of the Appalachian Mountain system. As the Cordilleran arc developed, a new back arc basin formed behind the McCloud arc.
View to west of above. Pacific subduction continues below North America
These maps present a contrasting hypothesis to the ones shown above