Alleghanian orogeny Alleghanian orogeny The Alleghanian orogeny or Appalachian orogeny is one of the geological mountain-forming events that formed the Appalachian Mountains and Allegheny Mountains. The term and spelling Alleghany orogeny was originally proposed by H.P. Woodward in 1957. The Alleghanian orogeny occurred approximately 325 million to 260 million years ago over at least five deformation events in the Carboniferous to Permian period. The orogeny was caused by Africa colliding with North America. At the time, these continents did not exist in their current forms: North America was part of the Euramerica super-continent, while Africa was part of Gondwana. This collision formed
Cadomian Orogeny typical structure. After the orogeny, continental sediments were washed on top of the deformed Cadomian rocks. They include conglomerate and sandstone in Brittany, Jersey and Alderney. The Cap Frehel red beds are dated at . These post orogeny deposits were dumped from braided stream channels. The basins for these sediments followed the structural grain in the Cadomian Orogeny. There are two overall models for the formation of the Cadomian Orogeny. Firstly by Jean-Pierre Brun & P. Bale that compression to the south west of a volcanic arc and back arc basin onto the edge of the continent at the St