Gravity and multichannel seismic reflection constraints on the lithospheric structure of the Canary Swell

Deep penetrating multichannel seismic reflection and gravity data have been used to study the lithospheric structure of the Canary Swell. The seismic reflection data show the transition from undisturbed Jurassic oceanic crust, away from the Canary Islands, to an area of ocean crust strongly modified by the Canary volcanism (ACV). Outside the ACV the seismic records image a well layered sedimentary cover, underlined by a bright reflection from the top of the igneous basement and also relatively continuous reflections from the base of the crust. In the ACV the definition of the boundary between sedimentary cover and igneous basement and the crust-mantle boundary remains very loose. Two-dimensional gravity modelling in the area outside the influence of the Canary volcanism, where the reflection data constrain the structure of the ocean crust, suggests a thinning of the lithosphere. The base of the lithosphere rises from 100 km, about 400 km west of the ACV, to 80 km at the outer limit of the ACV. In addition, depth conversion of the seismic reflection data and unloading of the sediments indicate the presence of a regional depth anomaly of an extension similar to the lithospheric thinning inferred from gravity modelling. The depth anomaly associated with the swell, after correction for sediment weight, is about 500 m. We interpret the lithospheric thinning as an indication of reheating of old Mesozoic lithosphere beneath the Canary Basin and along with the depth anomaly as indicating a thermal rejuvenation of the lithosphere. We suggest that the most likely origin for the Canary Islands is a hot spot. © 1995 Kluwer Academic Publishers.The seismic and gravity data were acquired by the vessel Geco-TAU. The Instituto Geogrfifico Nacionalof Spain (IGN) financed data acquisition and processing by GECO A.S. The seismic data were partially processed by GECO and at Lamont-Doherty Earth Observatory. Support by J. Alsop, N. Bangs, R Buhl, R. Foreman, J. C. Mutter and C. Z. Mutter duringprocessing at LDEO is greatly appreciated. Discussion with T. Reston is greatly appreciated. Some of the figures of this paper were made with GMT software (Wessel and Smith, 1992). C. R. Ranero was supported by the Departament d'Ensenyament de la Generalitat de Catalunya when at ICTJA