The Galicia Margin Galicia Margin is a starved passive ocean margin with a thin sediment above acoustic basement.
Rift structures control the present-day morphology.
The continental basement is broken by normal, possibly listric, faults into narrow, elongate tilted blocks trending north and dipping gently east, forming a series of half grabens. On the western, uplifted side of some blocks, basement and possibly pre-rift sedimentary rocks crop out. Tithonian limestones, resting either directly on basement or on a thin basal conglomerate overlying the basement, implies that this region remained a structural high until late in the Jurassic. This peridotite could be part of a Hercynian ophiolitic slab included in a tilted block of the continental crust or, more likely, it was emplaced during late rifting of the margin as a result of the stretching of the lithosphere.