Alternating crustal architecture in west Iberia; a review of its significance in the context of NE Atlantic rifting

The crustal architecture of the Western Iberian Margin is investigated so that the relationship between synrift intra-plate segmentation, magmatic events and subsequent margin convergence can be discussed in the context of the evolution of the Central-North Atlantic Ocean. The evidence in this paper indicates distinct crustal architectures for NW Iberia (lower-plate) and SW Iberia (upper-plate), as shown by (1) the different geometries of the rotated tilt-blocks across thinned continental crust, (2) the distinct dips of deep crustal detachments and (3) the presence of first-order strike-slip zones bounding different crustal segments. We demonstrate that a switch in the dip direction of the crustal detachment is accomplished by accommodating persistent transcurrent deformation along first-order transfer zones and associated uplifted hinges, both of which accommodated synrift displacement and post-rift margin inversion. This alternating architecture explains why recurrent magmatism is conspicuously located on the upper-plate margin, which we consider to have favoured, in discrete pulses, the emplacement of magma. Finally, the crustal detachment underlying the upper-plate is interpreted to have been reactivated since the Eocene as the weak zone accommodating ocean-continent convergence and the putative onset of margin subduction. Supplementary material: Summary of the three main magmatic events on the onshore and offshore West Iberia and their associated occurrences, location and magmatism type, in relation with the syn- to post-rift evolution of the margin are available at https://doi.org/10.6084/m9.figshare.c.3591209