Pre-drift extension of the Atlantic margins of North America and Europe based on paths of Permo-Triassic apparent polar wander

Abstract

We reconstruct the relative configuration of North America and Europe prior to separation using paths of apparent polar wander (APW) for the interval 300 to 200 Ma. The Bullard et al. (1965) reconstruction closely superimposes the 300 Ma points on the two APW paths but leaves the 200 Ma points far apart. Conversely, anomaly-based reconstructions for later times approximately superimpose the 200 Ma ends of the paths but leave the older ends far apart. This indicates that separation of the interiors of the two continents began during the interval 300 to 200 Ma, long before surficial rifting commenced in the late Mesozoic. This in turn requires pre-rift extension in the two continental margins. Extension appears to have occurred in two phases of approximately equal magnitude but significantly different direction; the change in direction occurred at about 200 Ma. The earlier (300 to 200 Ma) episode of extension appears to have involved a strong element of sinistral shear. Based on our preferred reconstruction, the total amount of pre-rift extension of the two continental margins may have been as much as 1400 km.