The earliest tectonic structures recognized in northern and western Gaspé Peninsula are intrafolial, isoclinal folds with an axial-surface schistosity or slaty cleavage closely parallel to bedding. Most of these structures are confined to low-grade metamorphic rocks in the lower part of a Cambro–Ordovician volcanic and flysch succession; locally they affect rocks of a formation that is dated elsewhere as mainly Middle Ordovician. Later folds of variable shape and size, usually with steep axial surfaces, affect all the succession. Both fold sets are reinterpreted to have developed during the Taconic orogeny (mid to late Ordovician).Acadian (mid-Devonian) folds in cover rocks trend closely parallel to those in the Taconic basement, but deformation of the basement was mainly limited to late warping, which formed major anticlinoria and synclinoria that determine the outcrop pattern.