Relative displacement between Eurasia and North America prior to the formation of oceanic crust in the North Atlantic

Abstract

The relative positions of North America and Eurasia prior to the opening of the North Atlantic can be reconstructed using three independent data sets: ocean-floor magnetic anomalies and fracture zones, the shape of the shelf line at the continental margins of North America and Eurasia, and the apparent polar wander paths (APWPs) of these two continents together with geological constraints. We here examine the internal consistency of these reconstructions, discuss the tectonic implications of the inconsistencies, and show how all three data sets can be combined to obtain a best fit reconstruction pole. In our analysis we find that the combined errors of the new North American and European APWPs are smaller for 290-240 Ma than at earlier or later times. Therefore this interval was used. Rotation poles derived from magnetic anomalies from the North Atlantic do not bring the APWPs into coincidence. A rotation pole located at 88°N, 215° E with rotation angle −42°, superimposes the two APWPs and is reasonably consistent with the geology of the continental margins in the North Atlantic. The difference between the rotation pole based on APWPs and that based on magnetic anomalies probably reflects relative motion of the two cratons between the Early Triassic and the Late Cretaceous, cratonal Germany moving about 800 km to the east relative to North America and Norway moving about 500 km northeast relative to Greenland. This motion is expressed in extension in the North Sea and the continental shelves. On the other side of the globe, in the vicinity of Siberia and Alaska, our reconstruction places cratonal North America farther away from cratonal Eurasia than do reconstructions based on North Atlantic magnetic anomalies. This greater separation is consistent with the presence in the Late Paleozoic and Early Mesozoic of a sea way in Siberia located in the gap between Eurasia and North America. The magnitude of this gap is uncertain because of Mesozoic deformation in Alaska, and Siberia.