New insights into the Devonian palaeogeography of the North Atlantic region by detrital zircon geochronology

In the aftermath of the Caledonian orogeny, several extensional intramontane basins developed in the North Atlantic region. Thick successions of red-bed sediments formed within those basins during the Late Silurian to Early Carboniferous recording the late stages of the Caledonian orogeny. Previous studies have suggested that the basins were interconnected sub-basins similar to the basins in the Basin and Range Region of the United States. Here we present new detrital zircon age and conventional petrographic heavy mineral data to gain insight into the sediment pathways in this region and the provenance of some Devonian continental successions from NE Scotland, E Greenland and SW Norway.

Previous studies on the sediments of the Clair Basin, west of the Shetland Isles, led to a subdivision of the sediments into three groups based on the relative abundance of ‘Caledonian’, Proterozoic and Archaean zircons and the relative abundance of heavy minerals. The Archaean dominated ‘Group 2’ was derived from the local Archaean metamorphic basement, whereas the other groups seem to have more distal source areas. Sediments from the Orcadian Basin show age spectra similar to the Proterozoic dominated ‘Group 1’ of the Clair Basin, indicating a common source area for these two sub-basins for at least part of their history. Detrital zircon age spectra from sediments from Canning Land in East Greenland are also dominated by Proterozoic zircons. However, some differences in age spectra indicate a similar but probably not the same source area for the sediments from NE Scotland and Greenland. Samples from Norway are also similar to ‘Group 1’, but heavy minerals indicate a local source for these sediments.

The detrital zircon age data indicates that rather long rivers were draining the basement of the East Greenland Caledonides, transporting material as far as NE Scotland. Nevertheless, differences in zircon age patterns in the sub-basins of the NE Scotland region and within the sediments from Canning Land show that additional local drainage also played a role. The Devonian basins of the Norwegian Caledonides on the other hand seem to have had no or only a limited connection with the basins to the east.