Subduction related structures in the North Iberian Margin

The oblique convergence of Eurasia and Iberia since the Early Cretaceous, caused the formation of the Pyrenean intracontinental collisional orogen in the east, and progressed to continent-ocean collision with subduction of the Bay of Biscay oceanic crust beneath the North Iberian Margin in the west: Two deep multichannel seismic profiles (IAM-12 and ESCIN-4), integrated with gravity modeling and other geological and geophysical data, provide the crustal-scale architecture of this margin and its tectonic evolution during the convergence. The North Iberian Margin is modeled with a south or south-southeast dipping oceanic crust beneath the outer part of,the continental shelf. Mesozoic basins an the shelf were inverted during the Tertiary, and compressional activity continued until recent times in the ESCIN-4 section, while a shallower, probably Neogene age basin is subjected to active recent erosion in the IAM-12 section. In the oceanic areas, a marginal trough deepens and widens toward the east as a result of the regional east dip of the oceanic basement. The:accretionary prism increases iri size from west to east (18-56 km), and its internal structure and morphology varies along Strike. The prism is buried by postconvergence sediments in both sections and in the IAM-12 section appears to have been active at least during Lutetian to Burdigalian times. The crustal-scale structure of the North Iberian Margin is that of an arrested subduction zone in which a remnant oceanic basin was being consumed near two continental plates that collided obliquely.