Abstract An analysis of the magnetic anomaly profiles in the Bay of Biscay provides evidence for the former existence of an E-W trending sea-floor spreading axis in Biscay. Identification of the magnetic anomalies indicates that the opening of the Bay of Biscay took place during the Cretaceous, between Barremian and Maestrichtian times, and involved the formation of a triple-ridge junction with the Mid-Atlantic Ridge between 80 and 73 m.y. ago. The asymmetric distribution of magnetic anomalies in the Bay of Biscay is confirmed. This evidence, together with a proposed Lower Cretaceous development of the Mid-Atlantic Ridge suggests that Biscay evolved as a result of a three-phase rotation of Iberia.