The redox state of atmosphere-ocean system is strongly coupled to the evolution of the climate that likely controlled biological innovation. The neoproterozoic ERA (~1,000-542 MYR ago) was a period of…

This $474,659.98 grant was awarded by the National Aeronautics and Space Administration (NASA) to Florida State University (FSU) to conduct research on the relationship between ocean-atmosphere oxygenation and the evolution of multicellular life during the Neoproterozoic Era (~1,000-542 million years ago). The project will utilize vanadium isotopes as a proxy to track changes in marine low oxygen conditions over this critical period of environmental change and biological innovation. By investigating sedimentary vanadium isotope signatures, the researchers aim to better constrain the redox state of ocean environments before and during Cryogenian glaciations, as well as fluctuations in oxygenation during the Ediacaran. This research has the potential to provide important insights into the links between global climate shifts, ocean chemistry, and the emergence of complex life forms. The grant does not utilize any set-aside designations.

The redox state of atmosphere-ocean system is strongly coupled to the evolution of the climate that likely controlled biological innovation. The neoproterozoic ERA (~1,000-542 MYR ago) was a period of drastic environmental change with at least two low-latitude 'snowball earth' glaciations and carbon cycle perturbation as observed in carbon isotope fluctuation. Evidence has shown that the atmospheric oxygen increased from ambiguously low concentrations to near modern levels prior to the phanerozoic which likely had a major effect on the organic carbon burial, remineralization rate and carbon isotope record. Coupled to this large environmental shift is the observed evolution of complex multicellular life. These broad observations have documented the connections among large scale environmental change, ocean-atmosphere oxygenation and the evolution of the life. Even with an intense dedicated to understanding earth's oxygenation􀁇timing, initial rise of ocean oxygenation and quantification􀁇remains ambiguous largely due to proxy limitations. IT has been especially difficult to unambiguously track low oxygen environments in the paleo-ocean as current proxies lack the ability to uniquely track non-sulfidic low-oxygen conditions which is critical to unravel the mechanism(s) between atmosphere/ocean oxygenation, emergence and evolution of metazoans. The proposed project will focus on vanadium (v) isotopes in the NEO-proterozoic as a fingerprint for determining low oxygen, nonsulfidic conditions. The framework for this study is based on our modern v isotope signatures that capture variable bottom water oxygen conditions. We have observed remarkable v isotope variations of modern samples that are related to local bottom water oxygen contents. Importantly, the shift of the v isotope signature starts at suboxic (reduced but none-zero oxygen) conditions. Thus, sedimentary v isotopes, for the first time, have the potential to track changes in marine low oxygen conditions. Moreover, v concentrations begin enriching under low oxygen environments, thus the reductive enrichment of v in marine sediments occurs without the presence of sulfide. Modern observation also documents significantly different v isotope signatures between marine sediments and hydrothermal sediments, thus v isotopes can distinguish the mechanism of enrichment (redox or hydrothermal). Furthermore, given that v has a long modern marine residence time, the characteristic v isotope fractionation pattern has the potential to track the global oxygen content, when combined with other proxies. Thus, combining our current understanding of v systematics a high-resolution ancient study can illuminate sediment burial under low oxygen conditions. To track subtle low oxygen shifts in the neoproterozoic we will investigate the v isotope signature of shales ranging in ages from ~1,000 to 542 million years. IT is important to deconstruct this ~460 million years to capture the expansion and contraction of the local and global redox states of the ocean. In this proposal we seek to better constraint: (1) the redox state of the outer shelf VS. Deep basin settings before and during the cryogenian to better constrain the temporal and spatial (local VS. Global) relationships between the expansion of low oxygen regions and the earliest evidence of emerging of multicellular life (earliest record of demosponges), (2) the fluctuation of redox state during the ediacaran, to test the 'ocean oxygenation events' postulated for the end-marinoan glaciation. Extracting this information from ancient sediments has the potential to provide crucial information about the links between large scale environmental change (global glacial event), ocean oxygenation, hydrothermal activity and the evolution of animals. Developing v isotope to reconstruct low-oxygen paleo-redox conditions and the relationship to multicellular evolution could potentially be used to search for exoplanet life