Ancient scars and rotating ribbons: Appalachian–Caledonian orogenic influence on the genesis of the Flemish Cap and the Porcupine Bank during Mesozoic North Atlantic rifting

The Newfoundland–Irish Atlantic conjugate margin pair hosts more continental ribbons, failed rifts, and unusually sized and oriented sedimentary basins than anywhere else in the modern Atlantic Ocean. These margins also happen to have formed through rifting and break-up of the lithosphere that was involved in Appalachian–Caledonide orogenesis in the Paleozoic, with the Mesozoic propagating rift having impinged on the orogenic structures at an oblique angle. Here we combine results from 3D numerical modelling of oppositely propagating rifts, which are superimposed on deformable plate reconstructions of the southern North Atlantic. We propose that the rift oddities of the Newfoundland–Irish Atlantic conjugate margin pair resulted from the northward propagating rift responsible for the break-up of Pangaea reactivating Appalachian–Caledonide inherited structures under extension, effectively turning them into a southward propagating rift. The interaction of the two rifts caused the formation and clockwise rotation of a large continental microplate, which was ultimately split by a transform fault into two smaller clockwise-rotated mirrored continental ribbons, namely the Flemish Cap and the Porcupine Bank. The rotations of these continental microplates, which created the Orphan and Porcupine sedimentary basins and failed rifts therein, show the influence of inherited orogenic structures on subsequent rifting.