The St Lawrence Platform and Appalachian deformation front in the St Lawrence Estuary and adjacent areas (Quebec, Canada): structural complexity revealed by magnetic and seismic imaging

摘要

New magnetic and seismic datasets offer a unique opportunity to document the geometry of the Appalachian front in a poorly studied segment of the orogen. Interpretation of high-resolution magnetic data allows, for the first time, the documentation of the contact between the autochthonous St Lawrence Platform and the Appalachians and highlights the regional significance of previously poorly documented ENE faults that experienced post-Ordovician strike-slip motion. Seismic data reveal tectonic slices in the foreland domain underlying the Appalachians and show that the depth of the décollement at the base of the Appalachian tectonic wedge varies significantly. Taken together, geological, magnetic and seismic data suggest that the geometry of the Appalachian front exhibits significant variations in map and cross-section views and recorded a polyphased structural history.