HIGH SEISMIC VELOCITIES ASSOCIATED WITH REFLECTIONS FROM WITHIN THE LOWER OCEANIC-CRUST NEAR THE CONTINENTAL-MARGIN OF EASTERN CANADA

A deep seismic reflection profile on the continental rise off eastern Canada shows strong dipping reflections, apparently from within lower oceanic crust, over a region of limited lateral extent. The origin of these and similar reflections described elsewhere is uncertain. This paper reports new seismic-refraction results from the region of these reflections. They appear to be associated with a layer of P-wave velocity of about 7.4 km s-1 or higher, while the surrounding crust has a velocity ∼ 7 km s-1. The Moho, with velocity 8.1 km s-1, lies just below the reflectors, and the total crustal thickness is around 8 km. The crust is interpreted to be oceanic rather than continental, and the high velocities of the dipping reflectors are comparable to those of the mafic/ultramafic crust-mantle transition zone in the Bay of Islands ophiolite complex. © 1990.