Acadian Orogeny

The Acadian orogeny is a middle Paleozoic mountain building event (orogeny), especially in the northern Appalachians, between New York and Newfoundland. The Acadian orogeny most greatly affected the Northern Appalachian region (New England northeastward into the Gaspé region of Canada). The Acadian orogeny should not be regarded as a single tectonic event, but rather as an orogenic era. It spanned a period of about 50 million years, from 375 to 325 million years ago. In Gaspé and adjacent areas, its climax is dated as early in the Late Devonian, but deformational, plutonic, and metamorphic events extended into Early Mississippian time. During the course of the orogeny, older rocks were deformed and metamorphosed, and new faults formed and older faults were reactivated.

It was roughly contemporaneous with the Bretonic phase of the Variscan orogeny of Europe, with metamorphic events in southwestern Texas and northern Mexico, and with the Antler orogeny of the Great Basin.