Supracrustal faults of the St. Lawrence rift system between Cap-Tourmente and Baie-Saint-Paul, Quebec

The St. Lawrence rift system is made up of Late Proterozoic–Early Paleozoic supracrustal faults attributed to the opening of the Iapetus Ocean. The normal faults commonly occur at the contact between metamorphic rocks of the Grenvillian basement to the northwest and Cambrian–Ordovician strata of the St. Lawrence Lowlands to the southeast. Coastal sections of the St. Lawrence River that expose the Cap-Tourmente Fault and the St. Lawrence Fault have been studied between Cap-Tourmente and Baie-Saint-Paul. Fault rocks that mark these two normal faults consist of fault breccia, cataclasite, fault gouge, and pseudotachylyte. Field relations suggest that the various types of fault rocks are genetically related and associated to the same tectonic event. The comparison with faults characterizing the Charlevoix meteoritic structure indicates that brittle fault rocks are not limited to impact cratering, and that reactivation of the St. Lawrence rift system is a postimpact, probably Mesozoic phenomenon. CURRENT RESEARCH RECHERCHES EN COURS 2001 Article Article Titles Titres Purchase Information Information pour acheter 2001-D15 A. Tremblay and Y. Lemieux 1 1 Contribution to the Appalachian Foreland and St. Lawrence Platform NATMAP Project. 2 INRS Géoressources, Quebec Geoscience Centre, 880, chemin Sainte-Foy, C.P. 7500, Sainte-Foy (Québec) G1V 4C7