Motion of Iberia since the Late Jurassic: Results from detailed aeromagnetic measurements in the Newfoundland Basin

Abstract

A detailed aeromagnetic survey carried out in the Newfoundland Basin shows well developed seafloor spreading anomalies 24 to 34. Comparison of these anomalies with the corresponding anomalies in the Northeast Atlantic suggests asymmetric spreading from anomalies 31 to 34, with slower spreading in the Newfoundland Basin. Anomaly M0 is a very weak anomaly in the Newfoundland Basin compared to south of the Newfoundland Fracture Zone where it forms a prominent low within the large amplitude “J” anomaly. A similar behaviour of this anomaly is observed off Iberia. In the Newfoundland Basin it does not continue as far as the Flemish Cap but terminates in the vicinity of the Newfoundland Seamounts. The position of this anomaly as obtained here differs from previous identifications. The shapes of magnetic lineations in the Newfoundland Basin are significantly different from the corresponding lineations off Iberia. This has been interpreted as arising from shifts in the plate boundary between Africa and Eurasia during the time when Iberia was moving as part of the African plate. By combining the present data with other detailed survey data to the north we have been able to derive a plate kinematic solution for Iberia which shows that from the middle Cretaceous to the Late Eocene Iberia moved as part of the African plate and then as an independent plate until the Late Oligocene. Since then it has been moving as part of the Eurasian plate. During these times the boundary between Eurasia and Africa jumped successively from the Bay of Biscay accretion axis to the King's Trough-North Spanish Trough lineament to the Azores-Gibraltar Fracture Zone. The kinematic solution for Iberia so derived, from chron M0 to the present, not only explains the formation of some prominent bathymetric features in the oceanic regions, such as King's Trough, but equally well the formation of geological features on land, such as the Pyrenees. The difficulties in deriving a kinematic solution for Iberia for times earlier than chron M0 are discussed and a speculative position of Iberia at the time of its initial separation from the Grand Banks of Newfoundland is proposed. Furthermore, with the availability of a well-constrained model for the motion of Iberia, it should now be possible to relate more accurately the relative motions among Eurasia, Iberia and Africa to the history of the Mediterranean region.