C, Sr, Nd isotope chemostratigraphy and zircon provenance of the Witvlei Group (Namibia): Neoproterozoic glaciations and seawater evolution

The Neoproterozoic witnessed several low latitude glaciations (i.e., the Sturtian, Marinoan and Gaskiers glaciations) geodynamic reorganization of cratonic blocks after breakup Rodinia. Trace element stable isotope geochemistry from approximately coeval carbonate deposits on continental marginal sea foreland basins (Yangtze Platform, China; Otavi Nama Groups, Namibia) have shown fluctuating oxygen increase marine shelves. To gain an increasingly global picture bio-geochemical conditions in late seawater, we here present new redox-sensitive trace element, (C, O) radiogenic (Nd, Sr) records carbonates Cryogenian Blaubeker Court, Ediacaran Buschmannsklippe Formations (Witvlei Group, Namibia). Shale-normalised REE + Y patterns post-Sturtian post-Marinoan parallel modern seawater showing positive La, Gd anomalies. Negative Ce anomalies argue for their preservation more oxidising sea/porewater Witvlei Basin on. While underwent basin-fluid type overprinting, upsection record pristine Sr isotopic compositions that match curve. Partly coupled negative correlations between Nd suggest long-term shifts weathering short-term changes ocean circulation patterns. ?13Ccarb values range ?7.2 to +3.5 ‰ a excursion upper part stratigraphy. This might be equivalent ‘Shuram’ carbon (CIE). However, causes, extent correlation Shuram CIE are still debated. Typical putative less pronounced anomalies, lower Y/Ho ratios, bio-essential metal concentrations, arguing periodic redoxcline oscillations redox-stratified shelf environment. overall decrease enrichments throughout Group argues progressively increasing, presumably biologically-driven cycling towards typical Phanerozoic carbonates. combination local flux ambient redox may caused dynamic (bio)geochemical cycling, predating (and possibly promoting) metazoan radiation documented overlying Group.