An interpretation of a prominent magnetic anomaly near the boundary between the Eurasian and African plates (Gulf of Cadiz, SW margin of Iberia)

• Published in: Marine Geology
• Main Authors: Dañobeitia, Juan José, Bartolomé, Rafael, Checa, A., Maldonado, Andrés, Slootweg, A.Peter
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier 1999
• Subjects: Magnetics; Seismic gravity; Guadalquivir Bank; Gulf of Cadiz; Iberian Margin; Rif; North Atlantic
• Online Access: http://hdl.handle.net/10261/200224; https://doi.org/10.1016/S0025-3227(98)00140-6

15 pages, 10 figures, 1 table The Gulf of Cadiz is located at the boundary between the Eurasian and African plates in the southwestern margin of Iberia, and it straddles a place of major tectonic events since the Mesozoic. The Gibraltar belt migrated westward into the Gulf of Cadiz during the Miocene, while a north–south trending margin was built upon allochthonous formations at the western end of the Betic–Rif orogen. The geological setting of the Gulf allows a study of both the Mesozoic and Cenozoic evolution of the contact between these two major plates. This study reports a regional geophysical survey with an interpretation of the magnetic results, using a 2D modelling, constrained by recently acquired multichannel seismic profiling (MCS), and gravity data. From the magnetic pattern the area can be subdivided into three sectors which may be the expression of different geological provinces. In the eastern sector we find relatively small anomalies (∼50 nT), interpreted as the magnetic expression of the morphological ridges and valleys intersecting the central Gulf of Cadiz. In the southern sector, where data are scarce, we find a smooth magnetic zone with large-wavelength anomalies. The western sector, dominated by the Guadalquivir Bank, is where the largest magnetic anomalies are observed. The Guadalquivir Bank is a structural high which represents the offshore extension of the Hercynian Iberian Massif. We have interpreted a large-amplitude magnetic anomaly, of more than 300 nT (peak-to-peak) with a very steep gradient trending northward, to be caused by an intrusive material with an average estimated susceptibility distribution of 0.035 (SI). From the model studies, we believe that the magnetic source lies southwest of the Guadalquivir Bank, and is mainly composed of crustal material. The material rises up to 4 km depth, and probably was uplifted prior to the initial opening extensional stages of the central North Atlantic during the Triassic This study was supported by the U.S. Spain Joint Committee for ...