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 N eoproterozoic supercontinent oblique to interior collisional orogenic sutures associated with supercontinent amalgamation. As a result, part s of the Avalonian-Cadomian orogenic belt are likely to have evolved u pon different cratonic basements. Available Nd and U-Pb (detrital zirc on) isotopic data support this contention and suggest that West Avalon ia lay adjacent to the Amazonian craton during the Neoproterozoic, whe reas Cadomia and, possibly, East Avalonia occupied positions adjacent to the West African craton. Such variations in basement isotopic signa tures provide important information for Neoproterozoic paleogeographic reconstruction of the now-dismembered orogenic belt and may be of mor e general application to the palinspastic restoration of dispersed Pre cambrian terranes.