Reconstructing the Variscan basement under the West Iberian Margin and the Newfoundland conjugate Margin: exploring the role of tectonic inheritance

The Variscan–Alleghanian Orogen was broken apart by the Mesozoic opening of the Atlantic Ocean. The result is a complex structure that presents a challenge to the reconstruction of the orogen, often leading to models that may not fully account for the overprinting extensional system. Remnants of the Variscan–Alleghenian Orogen at present are encountered in onshore Iberia and the Atlantic seaboard of Canada, and offshore in the West Iberian Margin (WIM) and the Newfoundland Margin (NFM). These conjugate margins (WIM and NFM) exhibit strong structural variability along strike. While previous studies have explored inherited crustal structure, the precise link between the pre-rift crustal structure and the Variscan Orogen remains unexplored. We restore offshore domains to their pre-rift state and analyse how basement characteristics, inferred from geophysical properties, correlate with the development of extension in the conjugate margins. We estimated the amount of extension of the margins, how it partitioned into the upper and lower crust, and how this balanced with the overall crustal extension. This study correlates onshore and offshore basement domains and provides a novel reconstruction of the Variscan–Alleghenian Orogen across the central Atlantic Ocean. The proposed zonation of the Variscan–Alleghenian basement suggests an oblique orogenic system to the rift, offering new insights into the variability along strike in the WIM–NFM conjugate system and highlights the importance of understanding the Variscan basement and Avalonian terranes’ lithological composition and its influence on rift geometry.