Zinc, carbon, and oxygen isotopic variations associated with the Marinoan deglaciation

Abstract The "Snowball Earths" were cataclysmic events during the late Neoproterozoic's Cryogenian period (720-635 Ma) in which most, if not all, of Earth’s surface was covered ice. Paleoenvironmental reconstructions these utilize isotopic systems, such as Δ 17 O and barium isotopes barites. Other zinc (Zn), can reflect seawater composition or environmental conditions (e.g., temperature changes) biological productivity. We report here a multi-isotopic C, O, Zn data set for carbonates deposited immediately after Marinoan glaciation (635 from Otavi Group northern Namibia. In this study, we chemically separated calcite non-calcitic carbonate phases, finding isotopically distinct carbon oxygen isotopes. These could changes source formation. Our key is largescale variations over oldest parts distal foreslope cap sections. magnitude variation larger than any found throughout post-snowball to date, far shorter sequence. This shows heretofore undiscovered difficulty interpretations. primary sources are likely be aeolian alluvial, associated with massive deglaciation related run-off thawing continent greater exposed atmospheric aerosol entrainment. samples lightest compositions (δ 66 < 0.3 ‰) potentially hydrothermally sourced dominating carbonates’ budget. unique carbonates, when meltwater lid thinnest waters most prone upwelling dominated Snowball Earth brine. On other hand, local bioproductivity affecting seawater. Similarly, fluctuations sea-level bring depositional site below above redoxcline, causing variations. isotope ratios preclude estimation global signature, indicating localized resumption export production.