Unusually fracture-free seafloor in the southern North Atlantic between Newfoundland and Iberia explained through compounding tectonic inheritance since the Paleoproterozoic

Abstract

The seafloor between Newfoundland (eastern Canada) and Iberia (southwestern Europe) is unusually devoid of fracture zones compared to other parts of the Atlantic Ocean. Given that oceanic fracture zones commonly spatially correlate with inherited lithospheric weaknesses onshore, their absence may be suggestive of margins with stronger, broader, and more homogeneous inherited lithospheric structures. Herein, the smooth fracture-free seafloor is attributed to the long-lived influence of the massive St. Lawrence promontory, which (1) formed during Paleozoic Iapetan rifting, (2) subsequently controlled the spatial and temporal evolution of Appalachian orogenesis, and (3) ultimately predetermined the geometry of the Grand Banks continental shelf and the location of the Newfoundland-Azores fracture zone during Atlantic rifting and seafloor spreading. Further still, based on the spatial distribution of the adjacent Precambrian cratons and orogenic belts within ancestral Laurentia, the formation of the St. Lawrence promontory itself is attributed herein to inheritance from earlier episodes of Paleoproterozoic orogenesis during the building of Laurentia and during the amalgamation of the Rodinian supercontinent, suggesting that the influence of lithospheric inheritance on subsequent tectonism may persist and be detectable for almost two billion years and through multiple Wilson cycles.