Migrated sections of lithoprobe lines 52, 53, and 54. Interpretation of the main features of the reflection profiles. The Moho is marked by a dashed line. The continuous lines indicate reflections or significant changes in crustal reflectivity that mark terrane boundaries. A number of reflections within crustal units are highlighted to show the general orientation of reflectivity. Identification of the major crustal units. The thick shaded lines (E) represents the possible reactivation in extension of the major crustal thrusts at the Grenville Front. Abbreviations are SP, Superior Province; GF, downward projection of the Grenville Front; X, downward projection of SE edge of X terrane; GFZ, Grenville Front Zone; BA, Bouchette anorthosite; AP, Archean-Proterozoic boundary; BR, Baskatong ramp; LSZ, Labelle shear zone; MA, Morin anorthosite; MSZ, Morin shear zone; M, reflective lower crust; UD, upper decollement; LD, lower decollement; A/P?, affinity of lower crust, Archean or Proterozoic.