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Two seismic refraction lines were shot subparallel to the continental shelf edge off Nova Scotia using Ocean Bottom Seismometers as receivers; one line lies across Banquereau Bank while the other one is located approximately 170 km seaward of Sable Island over the foot of the continental slope. Models of crustal structure presented here are developed on the basis of results from travel time analyses, using layered model techniques, the tau-p extremal inversion technique, and ray tracing. Sonic logs from three nearby exploratory wells are utilized as additional constraints in deriving a satisfactory model of the geological section beneath Banquereau Bank.

The model shows that Upper Triassic and Lower Jurassic salt deposits beneath Banquereau Bank are at least 2.3 km thick; sedimentary rocks below may reach a thickness of 7 km unless part of this layer is comprised of Meguma basement. Only one seismic velocity, which could represent either unit, is found for this layer. The major crustal layer has a seismic velocity of 6.3 km s-1 beneath Banquereau Bank; the depth to its top surface is about 9.5 km in the west and 16 km in the east of this survey area.

The profile over the continental slope, although unreversed, reveals a 7.8 km thick sedimentary sequence, then a clear break to a 5.94 km s-1 velocity identified with a 1.7 km thick oceanic layer 2, and a velocity of 7.79 km s-1, which could represent either oceanic layer 3 or mantle at a depth of 9.5 km.

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Supervisor: Charlotte Keen