Seismic refraction observations on the continental boundary west of Britain

Three short (28 km) reversed and end-to-end refraction profiles and one long (125 km) reversed profile were made on the continental shelf west of Britain in 1960. The results are presented in two structure sections. The short profiles show layers of young rocks and recent sediments having compressional wave velocities of 1.66 to 2.99 km/sec that overlie a relatively thick (1.5 to 2 km) section of Paleozoic and basement metamorphic rocks. The relief of the basement surface is not reflected in these overlying layers. The long profile shows a thick layer having 6.1-km/sec velocity overlying material of velocity about 7.7 km/sec at depths of 26 km and 15 km at the south and north ends, respectively. This could be interpreted as an intermediate layer rather than the mantle normally defined by velocities of 8.0 km/sec or greater.