What was the Alleghenian orogeny?

The Alleghenian orogeny was a major mountain-building event that occurred primarily during the Permian Period (approximately 299 to 251 million years ago), resulting in the formation of the Appalachian Mountains.1

This orogeny was driven by the collision of the North American continental margin with that of North Africa, a process that played a key role in the amalgamation of the supercontinent Pangaea. The event is most prominently recorded in the central and southern Appalachians, where it caused significant compressional folding and faulting, including the westward thrusting of the Blue Ridge over the Ridge and Valley Province. Additionally, the collision produced igneous intrusions and metamorphism within the Piedmont Province. While its effects are less pronounced in the northern Appalachians, evidence of the orogeny persists along the east coast of New England and parts of the Canadian Maritime Provinces.12