Preliminary results of a seismic refraction study in the meriadzek-trevelyan area, bay of biscay

Seismic refraction studies over the Meriadzek-Trevelyan area in the north of the Bay of Biscay have established four main geological sequences : Cenozoic (1.9 to 2.8 km/s) ; Cretaceous (3.2 to 4.0 km/s); lower to middle Mesozoic (4.5 to 5.0 km/s) ; pre-Mesozoic (5.4 to 6.3 km/s). These agree broadly with the adjoining Western Approaches and English Channel areas to the northeast. The sub-sedimentary structure between the Meriadzek Terrace and the Trevelyan escarpment is of continental origin having a block-faulted pattern and is interpreted as a southwestward prolongation of the continental structure. The blockfaulted form is considered to have originated during the rifting of the Armorican Continental margin and may have been influenced by a tectonic pattern caused by the earlier activity of the South Armorican shear zone. [NOT CONTROLLED OCR]