The Ascot–Weedon Formation and Magog Group are part of the Cambro-Ordovician oceanic domain of the Quebec Appalachians. The purpose of this work is to define the stratigraphic and structural relationships that exist between these units and the Siluro-Devonian sedimentary rocks: the Lac Aylmer Formation, to the northwest, and the St-Francis Group, to the southeast. Two structural domains are defined in the area. The first one, the northwestern zone, is essentially autochthonous. The Magog Group units are overlain by the Siluro-Devonian sediments of the Lac Aylmer Formation. Both units make up the northwest flank of the St-Victor Synclinorium, plunging slightly to the southwest. The second domain, to the southeast is made up of allochthons (Ascot–Weedon Formation and St-Francis Group) thrust on a large part of the southeast flank of the St-Victor Synclinorium. Structural analysis at mesoscopic, microscopic, and macroscopic scales indicates that the Ascot–Weedon Formation and the St-Francis Group are thrust northwesterly on southeast-dipping imbricate faults. Rocks of both units underlie the major La Guadeloupe Fault, bringing the Connecticut Valley – Gaspé Synclinorium over the St-Victor Synclinorium.