Crustal structure across the Southwest Newfoundland Transform Margin
A seismic-refraction survey providing deep crustal structure information of the continent–ocean boundary across the South-west Newfoundland Transform Margin was carried out using large air-gun sources and ocean-bottom seismometer receivers. Continental crust ~30 km thick beneath the southern Grand Banks (P-wave velocity = 6.2–6.5 km/s) thins oceanward to a 25 km wide transition zone. In the transition zone, Paleozoic basement of the Grand Banks (5.5–5.7 km/s) is replaced by a basement of oceanic volcanics and synrift sediments (4.5–5.5 km/s). Seaward of the transition zone the crust is oceanic in character, with a velocity gradient from 4.7 to 6.5 km/s and a thickness of 7–8 km. Oceanic layer 3 is absent. No significant thickness of intermediate-velocity (>7 km/s) material is present at the continent–ocean transition, indicating that no under-plating of continental crust has taken place. The continent–ocean transition across the transform margin is much narrower than across rifted margins, supporting the ...