I describe a new 3D seismic dataset over the West Iberia margin that demonstrates the complex 3D architecture of hyperextended continental crust and exhumed continental mantle at the distal edge of the margin. Faulted continental crustal blocks show higher degrees of extension in the north than the south. Similarly, pre-tectonic sediments are cut by more small-scale normal faults in the north. I hypothesize that extension within the frontal basin was constrained by basement topography, specifically a small mantle ridge identified at the southern extent of the basin that may have obstructed the extension of the continental crustal blocks and overlying sediments. Several thrust faults also cut the pre-tectonic sediments and are interpreted to be the result of gravity-driven sliding during late-stage extension. After large-scale extension of continental crustal blocks, further extensional creep caused small-scale normal faulting of the pre-tectonic sediment in the north.