. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography S2S8 Dash et al.: Geophysical Investigation of the Cape Verde Archipelago 16'| â J\ v j â ^» â ,v. > CAP BLANC - ^ *y\ v v v^vu >",/. V. ^ . / , t 1/ 'v;-â¢*,;_, "'â¢:, ^"v^. CAPE VERDE ISLANDS. DAKAR Fig. 10. Magnetic anomaly map around Cape Verde Islands and continental shelf of Africa to 24°N. The Keathley sequences, a possible fracture zone, and the magnetic quiet zone boundary are indicated. No major bottom topograph
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography S2S8 Dash et al.: Geophysical Investigation of the Cape Verde Archipelago 16'| â J\ v j â ^» â ,v. > CAP BLANC - ^ *y\ v v v^vu >",/. V. ^ . / , t 1/ 'v;-â¢*,;_, "'â¢:, ^"v^. CAPE VERDE ISLANDS. DAKAR Fig. 10. Magnetic anomaly map around Cape Verde Islands and continental shelf of Africa to 24°N. The Keathley sequences, a possible fracture zone, and the magnetic quiet zone boundary are indicated. No major bottom topographic features occur along tne magnetic track lines. occurence of a typically oceanic layer 3 with a velocity of km/s^ (2) the presence of the magnetic quiet zone boundary landward of the islands [Rona et al., 1970]; and (3) the presence of open water aptychus limestone (Upper Jurassic-Lower Cretaceous) exposed on Maio similar to limestones recovered from analogous locations of the western North Atlantic deep ocean basin [Hollister et al., 1972]. The origin of the Canaries is closely linked with the faults through the islands [Dash and Bosshard, 1969]. The Cape Verde archipelago also originated as igneous intrusions and extru- sions along a fault system. The similarities between the Canary and Cape Verde islands end at the comparison of their crustal structures. Owing to a lack of any detailed seismic refrac- tion data in the area between the t^o island groups it is not possible to draw any extension of similarities between them. The magnetic signature of each of the two island groups is singularly distinctive. The Cape Verde islands lie west of the magnetic quiet zone, whereas in the Canaries the magnetic quiet zone passes through the island of Tenerife. The magnetic quiet zone almost follows the transitional crustal zone on the west coast of Africa. To reconcile the present transitional thickness and the inferred former oceanic composition of the crust beneath the
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