During ODP Leg 103, serpentinized peridotite (clinopyroxene-spinel harzburgite) was cored within the basement approximatively at the boundary between the North Atlantic oceanic curst to the west, and the thinned continental crust of the Galicia passive margin (Spain) to the east. The exposure of mantle derived peridotite on the seafloor occurred at the end of the period of rifting, roughly 110 Ma ago. Ductile shear zones observed in the cored peridotite are consistent with movements along a deep low-angle, normal fault rooted within the upper mantle and dipping eastward, beneath the Galicia margin. To explain the tectonic denudation of the mantle at the ocean-continent boundary, we use a non-uniform stretching model for the lithosphere, set up from the Wernicke's model (1985).

Deep sea drilling off the east coast of North America provided valuable information on the development of the continental rise in a region that has been influenced by the deposition of both continentally derived and pelagic sediments. Site 603 is interpreted to overlie Jurassic oceanic crustal basement. Based upon the oldest sediment recovered, Site 603 was only influenced by pelagic sedimentation during the late Berriasian to Valanginian, with terrigenous sediment not appearing until the late Valanginian to Aptian. The first evidence of clastic sedimentation is the development of a large turbidite system during a time when deltas were being built on the shelf. From the Hauterivian through the Late Cretaceous, black shale turbidites were intermittently deposited at this site. The maximum abundance of the carbonaceous clay stone occurs interbedded with red and green claystone, and some silt and sand turbidites, in the Aptian-Albian interval. Sea level rose during the Albian, and as a consequence redeposition of terrigenous sediment waned, then ceased. The site then dropped below the calcite compensation depth. Less extensive terrigenous turbidite deposits are found associated with multicolored noncalcareous claystone that represents pelagic sedimentation during the Late Cretaceous. A turbidite containing dark green spherules of montmorillonite, and anomalously high concentrations of Ni, Co, and As, is interpreted to represent exotic sediment that was reworked from the Cretaceous/Tertiary (K/T) boundary sediment, based on its sedimentological and geochemical similarities to a biostratigraphically dated K/T boundary lamina cored at DSDP Hole 390B on the Blake Plateau. Late Paleocene to early middle Eocene pelagic claystone is disconformably overlain by middle Miocene hemipelagic claystone. Turbiditic silts and clays accumulated at this site, followed by the development of the lower continental rise hills of the Hatteras Outer Ridge. This constructional feature formed from muddy contourites deposited from the Western Boundary Undercurrent. Terrigenous turbidites ponded landward of Site 603 and formed the adjacent continental rise terrace.

La campaña oceanográfica 103 del Ocean Drilling Program (ODP) ha estado dedicada a dilucidar la evolución tectónica y sedimentación del Margen Atlántico-Ibérico. Se realizaron un total de 14 sondeos., en cinco puntos de posicionamiento, sobre el extremo más profundo del margen; al S del Banco de Galicia. Los resultados obtenidos revelan que previamente al inicio de la expansión oceánica entre Terranova e Iberia ocurrió una historia compleja de distensión cortical, fracturación y subsidencia asociadas. Los resultados fundamentales son los siguientes: 1) Carbonatos de plataforma marina somera, de edad Jurásico superior-Cretáceo basal constituyen los primeros depósitos mesozóicos en ese ámbito del margen y dan lugar a un reflector sísmico considerado interiormente como basamento, 2) El hundimiento de la plataforma, fallamiento y basculamiento de los bloques ocurre desde 25 m.a. antes de iniciarse la acreción oceánica. 3) En el límite entre corteza oceánica-corteza continental se ubica una cresta constituida por peridotitas serpetinizadas. 4) El reflector sísmico «S», generalmente considerado como el límite dúctil-frágil en la corteza continental, corresponde realmente a la base de los depósitos sinrift.