Contrasting basement isotopic signatures and the palinspastic restoration of peripheral orogens: Example from the Neoproterozoic Avalonian-Cadomian belt

The Avalonian-Cadomian orogenic belt developed at the periphery of a Neoproterozoic supercontinent oblique to interior collisional orogenic sutures associated with supercontinent amalgamation. As a result, parts of the Avalonian-Cadomian orogenic belt are likely to have evolved upon different cratonic basements. Available Nd and U-Pb (detrital zircon) isotopic data support this contention and suggest that West Avalonia lay adjacent to the Amazonian craton during the Neoproterozoic, whereas Cadomia and, possibly, East Avalonia occupied positions adjacent to the West African craton. Such variations in basement isotopic signatures provide important information for Neoproterozoic paleogeographic reconstruction of the now-dismembered orogenic belt and may be of more general application to the palinspastic restoration of dispersed Precambrian terranes.