Structures sous-marines des bassins sédimentaires de Porcupine et de Rockall

In 1921 the "Pourquoi pas?" undertook, under the authority of J. Charcot, an identification of the Rockall bank (2). The petrographic nature of this relief was studied by Lacroix (2) who concluded to aegirine granite dated, since then, by Miller (3) and Sabine (4), from the early Tertiary period. At the beginning of the Noratlante cruise, in August 1969, the "J. Charcot" carried out a number of profiles, tallying the Porcupine and the Rockall area (fig.1). In addition to the gravimetry and magnetism recordings, an oblique-reflection profile and six Flexotir seismic-reflection profiles (with a frequency comprised of between 10 and 30 cycles) were carried out. We only present here the first results based on this last technique.