Alpine subduction and intraplate deformation along the Iberian Atlantic margins

The structure of Iberian Atlantic margins resulted from multiple Mesozoic rift events and subsequent contractional deformation occurring from the Upper Cretaceous to Cenozoic during the Alpine Orogeny. Along the southern Bay of Biscay, the North Iberian margin shows various styles of contractional deformation, ranging from mild reactivation of pre-existing extensional structures, halokynetic-related processes, to wedging and underthrusting. The Biscay accretionary wedge developed as the major structure at the base of the continental slope in the central and western parts of the North Iberian margin, which are part of the western branch of the Pyrenean-Cantabrian Orogen, together with the Cantabrian Mountains onshore. The wedge is interpreted to continue from the western North Iberian margin, where incipient subduction has been proposed, to the Galicia Margin further to the southwest. Along the West Iberian margin, thrusting and related folding and halokynetic-related processes focused contractional deformation.

In this work, we describe the seismo-stratigraphy, and we map contractional structures along the North Iberian and West Iberian margins based on the interpretation of 2D seismic reflection profiles. We identify and describe structural domains along the extinct subduction zone along the North Iberian margin, describe the structure of the fossil Biscay accretionary wedge, and identify and map different styles of Alpine contractional deformation along the North Iberian and West Iberian margins. We also describe the pre-existing Mesozoic rift structure in order to analyse the overprint between different rift architectures and contractional styles of deformation. The overall goal is to define different styles and stages of Alpine contractional deformation along Iberian Atlantic margins during the first phases of the convergent cycle preceding or leading to subduction.