A Devonian orogeny in the northern Appalachian mobile belt resulting from a collision of Baltica with Laurentia.

The Acadian orogeny is a middle Paleozoic deformation, especially in the northern Appalachians, between New York and Newfoundland. 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. The Acadian should be regarded, not as a single orogenic episode, but rather as an orogenic era.

A convergent mountain-building event, that occurred around 400 million years ago, during which continental slivers accreted to the eastern edge of the North American continent.