Sonoma orogeny Sonoma orogeny The Sonoma orogeny was a period of mountain building in western North America. The exact age and structure of the Sonoma orogeny is controversial. The orogeny is generally thought to have occurred during the Permian / Triassic transition, around 250 million years ago, following the Late Devonian Antler orogeny. The Sonoma orogeny was one of a sequence of accretionary events along the Cordilleran margin, possibly caused by the closure of the basin between the island arc of Sonomia and the North American continent. Evidence of this event has been reported throughout western North America, but most distinctly in
Sveconorwegian orogeny orogeny propagated eastward. There are differing views on the nature of the orogeny. One view, known as the "classical", postulates that a continent–continent collision, possibly with Amazonia, was responsible for giving the orogenic belts its current characteristics. An alternative view postulated in 2013 claims such collision did likely not occur as the characteristics of the orogen would be explained solely as the result of subduction and accretion of smaller terranes. These different views have implications for the configuration of the ancient supercontinent Rodinia. The southern part of what would eventually become the Western Gneiss Region of Norway formed migmatites and