Juxtaposition of the Mississippian Ristigouche and Cannes-de-Roches Basins, which are subbasins of the composite late Paleozoic Maritimes Basin, occurred through dextral movement along the northwest-striking Percé Fault system in the eastern Gaspé Peninsula of Quebec. The northwest-striking faults are truncated by small north-northwest–striking dextral strike-slip faults, which probably developed as regional stress gradually rotated clockwise from north-northwest–south-southeast to northeast-southwest. This study provides the first evidence in eastern Quebec for significant post-Acadian block displacement other than normal faulting and indicates that Alleghanian deformation extended much farther north than previously thought. Identification of these structures formed during the Alleghanian orogeny but more than 1000 km away from areas of peak Allegha nian metamorphism in the southeastern United States underlines the far-reaching effects of continental collisions. It also casts doubt on the age attribution of brittle strike-slip faults elsewhere in the Gaspé Peninsula, away from Mississippian exposures. Such brittle faults were previously associated with late stages of the Acadian orogeny but could in fact be considerably younger.