Results from the ESCI-N4 marine deep seismic profile in the northern Iberian Margin

The ESCI-N4 deep marine seismic profile is 145 km long and crosses the North Iberian continental margin in a N-S direction offshore Asturias. It records 20 s of near vertical seismic data that images the crustal structure of the continental platform and the transition to the deep sea areas of the southern Bay of Biscay. The reflectivity of the upper crust in the continental platform images the Mesozoic Le Danois and Ribadesella basins that include inverted structures developed during Tertiary times. These structures are northverging blind thrusts and associated growth folds developed above a south dipping detachment interpreted to be located near the base~ent-cover contact. To the North of the steep continental slope a thick sedimentary package is irnaged between 6 and 9.5 s (TWT) which includes a 50 km long, north-tapered wedge of mainly south dipping reflections corresponding to disturbed sediments within an Alpine-age accretionary prism. The oceanic-type basement dips gently landwards towards the deformation front beneath the prism, and an upper sedimentary package onlaps onto the prism suggesting the cessation of the tectonic activity in the prism that has been dated as Late Oligocene.