The Newfoundland margin crust: Understanding the Atlantic rifting.

The structure of the Newfoundland–West Iberian conjugate margins has been extensively studied during the past 50 years in hundreds of papers. The crustal structure has been evaluated through seismic surveys and drilling expeditions, but those are not equally distributed in Iberia and Newfoundland. More work, and in particular recent studies on the West Iberian margin, have identified a complex crustal architecture characterised by continental, oceanic, and exhumed mantle domains that vary along the margin. This structural complexity has only been recently documented with modern data that allow to image the basement domains in detail.

In contrast, the Newfoundland basement remains comparatively less well understood due to a relative scarcity of seismic and drilling data. The main wide-angle and streamer data for this area, the SCREECH survey, were acquired in 2000 and modelled under the computational limitations of that time. The resulting models and images have been subject to debate and failed to unequivocally define the nature of the basement domains of the margins. This uncertainty has left open key questions regarding the evolution of deformation during rifting and, thus, also the degree of symmetry of this conjugate pair of margins.

The SCREECH acquisition parameters were similar to modern marine acquisition standards. We leveraged their inherent data quality with the current computational facilities and up-to-date methodologies to re-process the data, imaging the structure and modelling seismic phases. Recent advancements in parallel computing and novel geophysical techniques now allow for enhanced-resolution seismic models and a mathematically robust uncertainty analysis—tasks that were previously very computationally demanding.

Our study utilises the original SCREECH field data, consisting of three transects with coincident multichannel seismic (MCS) reflection data (6-km streamer) and wide-angle data recorded by short-period OBS and OBH stations at ~15 km spacing. By performing a joint inversion of the streamer and wide-angle data (utilising both reflection and refraction arrivals), we significantly improved the definition of geological units and the spatial resolution of the velocity models. A statistical uncertainty analysis was conducted to validate the reliability of these observed features.

Our findings reveal previously unrecognised crustal heterogeneity at the Newfoundland margin, including significant variations in thickness and composition along the margin. Notably, we challenge prior classifications of the crustal domains and the location and dimensions of the Continent-Ocean Transition (COT). Previous models identified an intra-basement deep reflector as the Moho, defining a 4–5 km thick layer interpreted as continental crust. However, our results suggest this reflector may not represent the Moho, as the observed crustal properties are inconsistent with typical continental or oceanic crust, and rather support a COT formed by >250 km of exhumed mantle. By integrating MCS imagery with these new velocity models, we provide a re-interpretation of the margin’s crustal structure and propose a refined evolutionary model for the West Iberian–Newfoundland conjugate system.