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Mountain-building event that affected the Appalachian Geosyncline in the late Permian period (c. 286–248 million years ago). The Alleghenian orogeny is most pronounced in the central and southern Appalachian Mountains and produced the different effects in various subregions: compressional folding and faulting of the Valley and Ridge Province, westward thrusting of the Blue Ridge, and folding and minor metamorphism and igneous intrusion in the Piedmont Province. It may have resulted from the collision (see plate tectonics) of the central and southern Appalachian continental margin with that of North Africa in the Permian period.