Tectonic evolution of the emergent part of a volcanic ocean island: Lanzarote, Canary Islands

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A reconstruction of the structural evolution of Lanzarote confirms the existence of two principal stages of construction of the island, separated by a main erosional event. The first (pre-erosional) is the shield stage, Miocene-Pliocene in age, which is divided in three stratigraphic groups, where different formations can be distinguished using unconformities mappable over the whole area of outcrop. In the second (post-erosional) stage, developed during the Quaternary, nine stratigraphic levels are tentatively identified and are grouped in two phases of volcanic activity (Shields phase and Pyroclastic cones phase). Data from 580 photogeologic lineaments, as well as field data from 204 fault planes (195 with sense of movement), 273 dykes, and 45 volcanic alignments, are presented. The tectonic style of the deformations is brittle and polyphasic. Strike-slip faults are dominant, but normal and reverse faults are also present. Both the so-called “Atlantic” and “African” directions are well developed in trends of strike-slip faults and volcanic indicators. At least two deformation phases can be identified from the geometrical analysis of faults and from the stress tensor calculated using lineations on fault planes. The reconstructed stress field responsible for the measured deformations changed orientation during the evolution of the island of Lanzarote. It is suggested that a permutation between principal stress axes σ 1, and σ 3 occurred subparallel to the length of the island between the pre-erosional and post-erosional stages.