Conjugate no more: redefining the pre-rift relationship between the Flemish Cap and the Goban Spur prior to the North Atlantic opening

With increased geophysical scrutiny of the NE Newfoundland-Irish margin pair (North Atlantic), the previously assumed conjugate relationship and rift-perpendicular extension between the Flemish Cap and Goban Spur are increasingly questioned. We present multichannel reflection profiles along the Flemish Cap, the Porcupine Bank, and the Goban Spur, along which structural domains (proximal, necking, hyperextended, and/or exhumed mantle domains included) are defined. Features of each structural domain along these profiles on the Flemish Cap and the Goban Spur are strikingly different, whereas similar structural features are observed in the necking domains along seismic profiles on the Porcupine Bank and the Flemish Cap. The variability in basement features suggests oblique rifting between the Flemish Cap and the Goban Spur-Porcupine Bank region, as well as a connection between the Porcupine Bank and the Flemish Cap during Early Jurassic rifting. This understanding is consistent with crustal thickness evolution calculated from a deformable plate reconstruction model that is locally updated based on seismic interpretation constraints and previously published plate reconstructions. The updated deformable plate model shows varying extension obliquity between the Porcupine Bank, Goban Spur, and Flemish Cap, which are strongly influenced by inherited Caledonian and Variscan structures, resulting in the conclusion that the Flemish Cap and the Goban Spur were not conjugate margins prior to the opening of the modern North Atlantic Ocean.