This project aims at determining whether Neoproterozoic glacial terminations are characterized by extraterrestrial platinum group element (PGE) anomalies. The original data (Bodiselitsch et al., Science, 2005) are consistent with extraterrestrial iridium enrichments in terminal Sturtian and Marinoan sediments. In contrast, unpublished data for the terminal Marinoan sediments in the Mackenzie Mountains, NW Canada, show PGE anomalies that are of terrestrial pedigree. These terrestrial anomalies reflect significant changes in sedimentation rates from glacial diamictites into the overlying postglacial cap carbonates. Based on the existing data from both locations it is unclear whether extraterrestrial anomalies are common features at Neoproterozoic glacial terminations. This project is designed to test the pedigree of PGE in continuous, well-characterized sections across sections of Marinoan glacial terminations that represent a transect from shallow shelf to deep slope depositional settings in NW Namibia. The gradient in depositional environments makes it more likely that in at least one location the full glacial-postglacial transition ? and thus the hypothesized extraterrestrial iridium anomaly ? is preserved. If extraterrestrial enrichments of PGE are confirmed, follow-up studies are needed to better constrain the globally integrated magnitude of the anomaly. The spatial heterogeneity of these anomalies may also help to improve ice-sheet models for Cryogenian glaciations.
