Lithospheric breakup is generally defined as the process that results in a new plate boundary and oceanic crust. However, how this process occurs in magma‐poor systems remains debated. As recently suggested, the J‐magnetic anomaly at the Iberia–Newfoundland margins has polygenic sources and therefore cannot be interpreted as an isochron. However, the presence of the J‐anomaly on both margins suggests a common origin. By using analytic signal map of magnetic data, we highlight landward zigzagged limits for the J‐anomalies at the Iberian–Newfoundland margins. The zigzag segments neither match the axis nor the transform systems of previously proposed plate reconstructions, but are aligned with NE‐SW Palaeozoic trends. However, they can be fitted using recently published plate restorations, as expected if they have a single origin. Therefore, a link between the location of syn‐ to post‐breakup magmatic additions along the J‐anomaly and an inherited lithospheric trend is proposed.

ABSTRACT. Inheritance on continental lithosphere is considered as an important aspect on passive margins, since they may control magmatic budget and strain evolution during rifting and lithospheric breakup. On the distal Western Iberian margin, the transition to a steady state oceanic crust was little sampled and less investigated, in comparison to the more proximal parts near to the continental edge. In this work, we use marine magnetic data to analyze some aspects of the transition between the zone of exhumed continental mantle (ZECM) and the unequivocal oceanic crust, using transformed magnetic data. We observe that the end of the ZECM presents some straight magnetic features, especially at the eastern limit of the J anomaly. These magnetic lineaments are consistent with Early Cretaceous flow lines of the Iberian Plate. Straight structures are not expected in a newly formed oceanic lithosphere. Instead, it seems to be controlled by mantle inheritance. These straight magnetic features may indicate basement inheritance controlling magmatic insertions at the beginning of the oceanic crust formation.Keywords: Iberia, Magnetometry, Ocean-Continent Transition, Inherited Structures, Magma-Poor Margin. RESUMO. Estruturas herdadas na litosfera continental são um aspecto importante em margens passivas, pois poderão condicionar a entrada de magma e a evolução da deformação durante o rifteamento e quebra litosférica. Na porção distal da Margem Ibérica Ocidental, a transição da crosta continental até a crosta oceânica bem estabelecida possui menos dados e é menos investigada em comparação com a porção junto do limite de crosta continental. Neste trabalho, usamos dados magnéticos marinhos para analisar alguns aspectos entre a zona de exumação mantélica e a crosta oceânica inequívoca, através de dados magnéticos transformados. Observa-se que o final da zona de exumação mantélica apresenta algumas feições retilíneas, especialmente no limite leste da Anomalia J. Estes lineamentos magnéticos estão em conformidade com linhas de fluxo mesozoicas da Placa Ibérica. Feições retilíneas não são esperadas em uma litosfera oceânica neoformada. Ao contrário, estas aparentam ser um controle dado por estruturas pretéritas do manto. Portanto, estas feições magnéticas retilíneas sugerem uma herança do embasamento continental controlando as intrusões magmáticas no início da formação da crosta oceânica.Palavras-chave: Ibéria, Magnetometria, Transição Continente-Oceano, Estruturas Herdadas, Margem Pobre em Magma.

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