Abstract

We present the results of anisotropy of magnetic susceptibility (AMS) analyses carried out on weakly deformed Triassic red beds, Jurassic and Lower Cretaceous limestones, sandstones and shales from several northern Iberian Mesozoic basins located near the northern Iberian plate margin (Santander, Cabuérniga and Polientes basins in the western part of the Basque–Cantabrian basin, and Bilbao and Aralar basins in the central–eastern part; Cameros basin in the northernmost part of the Iberian chain). A well-defined magnetic lineation of tectonic origin is found at most of the sampled sites, and is interpreted as the stretching direction resulting from the extensional deformation characterizing this period. During the Mesozoic, the northern margin of the Iberian plate underwent two rifting stages, the Triassic and Late Jurassic–Early Cretaceous (Kimmeridgian–Albian) rifting events. Both the Triassic and the period of the Late Jurassic–Early Cretaceous rifting event with maximum subsidence rates (i.e. until the Barremian) are characterized by a NE–SW extensional direction in the main subsidence areas. This indicates that NW–SE master faults controlled basin subsidence and sedimentation through these periods in the northern Iberia plate margin basins. Conversely, during Jurassic and Aptian times a lower activity of NW–SE faults, together with more important extension along a NW–SE direction can be inferred from AMS analysis. This study indicates the power of AMS analysis in basin analysis and geodynamic reconstructions even in subsequently inverted basins.

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