The Canarian archipelago comprises seven main volcanic islands and several islets that form a chain extending for c.

No abstract

Measurements of dyke orientations and fault slip data have been taken in 39 stations located in the northern part of the island of La Palma (Canary Archipelago). These structures affect the materials belonging to the submarine growth stage and to the lower units of the subaerial shield volcano stage. Four sets of dykes have been distinguished (Groups I, II, III‐1, and III‐2). The two younger dyke groups (III‐1 and III‐2), with highly variable strikes, are clearly related to the subaerial growth stage. Most of the measured faults are normal. Field relationships and the use of stress inversion methods allowed us to separate three different stress tensors. Tensor 2 is associated with the dykes of Group III‐1. Given the spatial distribution of the stations with faults of tensor 2 and dykes of its coeval Group III‐1, it has been possible to obtain a map of trajectories of the maximum (SH) and minimum (Sh) compressive stress axes in the horizontal. Comparison between this map and the results of theoretical models suggests that the stress field active during, at least, the early stages of growth of the shield volcano in La Palma (from near 1.7 Myr to, at least, 1.2 Myr ago), includes a compressive radial (volcanic) component plus a regional tensile stress of a tectonic origin. This second component might be the imprint in the Atlantic oceanic lithosphere of the Cenozoic convergence between the African and Eurasian plates.

No abstract

The older geological units of the volcanic island of Fuerteventura (Canary Islands), i.e., the so‐called basal complex and the lower part of the subaerial volcanic rocks, show abundant structures indicative of a long‐lived period of Miocene tectonic activity. These structures include faults, dike swarms, kilometer‐scale folds, tilted sequences, and fissural and central volcanic edifices. A detailed structural study, based on geological mapping and the use of fault slip inversion techniques and statistical analysis of dike orientation, has allowed the identification of three separated Miocene deformation phases: M‐D1, M‐D2, and M‐D3. The average extension directions determined for these phases are NW‐SE, NNE‐SSW, and ENE‐WSW, respectively. A model of oceanic lithosphere rifting is proposed to account for this deformation history. A buoyant, anomalous sublithosphere mantle triggered the extension in the lithosphere beneath Fuerteventura, isolating it during the early and middle Miocene from the plate‐scale collision regime predominant in the NW corner of the African plate.