Nature of Crustal Necking and Rift Domain Architecture Along the Newfoundland Margin, Eastern Canada: Improved Seismic Perspectives and Interpretational Uncertainties

The Newfoundland rifted margin (NLRM) exhibits complex lithospheric features, including failed rifts, continental ribbons, transfer zones, and along-strike segmentation. Although the spatial variability of these tectonic features is central to understanding the region’s tectonic evolution, their interactions and broader implications remain debated. In this study, drawing on an unprecedented deep multichannel seismic dataset, we interpret a grid of margin-scale seismic reflection profiles to examine the variability of crustal necking and rift domain architectures along the NLRM and the associated Orphan Basin–Flemish Pass failed rift. Our interpretation reveals asymmetrical crustal necking on the conjugate sides of the failed rift, consistent with published numerical modelling studies, which suggest that asymmetric rifting is an early-stage process, potentially occurring before the necking phase. We observe more gradual crustal necking in regions of thinned and inferred weaker crust. In contrast, more abrupt crustal necking is associated with areas of thicker, inferred stronger crust, where transcrustal faults extending to depths greater than 20 km are imaged. Mantle serpentinization interpreted beneath both the NLRM and the failed rift zone indicates that serpentinization is not contingent on rift success or failure but is primarily governed by rheology and the availability of transcrustal faults. For magma-poor rifted margins, in contrast to magma-assisted rifting, transcrustal faulting linked with mantle serpentinization appears to facilitate continental breakup. Our systematic mapping reveals pronounced across-strike and along-strike variations in rift domain distributions, predominantly controlled by inherited transfer zones that segment the margin and that range from localized to diffuse, accommodating extension and giving rise to alternating strong and weak margin segments.