Post-rift compression on the SW Iberian margin (eastern North Atlantic): a case for prolonged inversion in the ocean-continent transition zone

An extensive grid of 2D seismic reflection data imaging the non-volcanic continental margin of SW Iberia is used to investigate the post-rift compressional evolution in the transition zone between continental and oceanic crust. Tectonic compression affected the margin almost continuously since the latest Cretaceous, but was predominantly focused during the mid-Eocene and the late Oligocene-mid-Miocene. The detailed interpretation of post-rift structures and their adjacent strata shows that crustal shortening in the various sectors of the margin is neither synchronous nor similar in style. Main post-rift structures include: (1) thick-skinned transpressional deformation on the distal margin; (2) localized basin shortening on the outer proximal margin; (3) limited reverse faulting and inversion on the inner proximal margin. The location and magnitude of crustal shortening are dependent on the inherited syn-rift geometry, the existence of evaporite (or clay-rich) detachments at depth, the rheological behaviour of previously extended continental crust and the position of the ocean-continent transition zone. The mechanisms of compression are mainly dominated by plate collision associated with the southeastern migration of the Iberian microplate during the Alpine orogeny and with recent westward convergence with the oceanic domain.