Temporal evolution of shallow marine diagenetic environments: Insights from carbonate concretions

Loyd, Sean J, Meister, Patrick, Liu, Bo, Nichols, Kevin, Corsetti, Frank A, Raiswell, Robert, Berelson, William, Shields, Graham, Hounslow, Mark ORCID: 0000-0003-1784-6291, Waldron, John WF
et al (show 2 more authors) (2023) Temporal evolution of shallow marine diagenetic environments: Insights from carbonate concretions. GEOCHIMICA ET COSMOCHIMICA ACTA, 351. pp. 152-166.

[img] PDF
Lloyd-concretions-final accepted-version.pdf - Author Accepted Manuscript

Download (6MB) | Preview


Early diagenesis of marine organic matter dramatically impacts Earth's surface chemistry by changing the burial potential of carbon and promoting the formation of authigenic mineral phases including carbonate concretions. Marine sediment-hosted carbonate concretions tend to form as a result of microbial anaerobic diagenetic reactions that degrade organic matter and methane, some of which require an external oxidant. Thus, temporal changes in the oxidation state of Earth's oceans may impart a first-order control on concretion authigenesis mechanisms through time. Statistically significant variability in concretion carbonate carbon isotope compositions indicates changes in shallow marine sediment diagenesis associated with Earth's evolving redox landscape. This variability manifests itself as an expansion in carbon isotope composition range broadly characterized by an increase in maximum and decrease in minimum isotope values through time. Reaction transport modelling helps to constrain the potential impacts of shifting redox chemistry and highlights the importance of organic carbon delivery to the seafloor, marine sulfate concentrations, methane production and external methane influx. The first appearance of conclusively anaerobic oxidation of methane-derived concretions occurs in the Carboniferous and coincides with a Paleozoic rise in marine sulfate. The muted variability recognized in older concretions (and in particular for Precambrian concretions) likely reflects impacts of a smaller marine sulfate reservoir and perhaps elevated marine dissolved inorganic carbon concentrations. Causes of the increase in carbon isotope maximum values through time are more confounding, but may be related to isotopic equilibration of dissolved inorganic carbon with externally derived methane. Ultimately the concretion isotope record in part reflects changes in organic matter availability and marine oxidation state, highlighting connections with the subsurface biosphere and diagenesis throughout geologic time.

Item Type: Article
Uncontrolled Keywords: Anaerobic oxidation of methane (AOM), Authigenic carbonate, Carbonate concretion, Methanogenesis, Organic carbon, Sulfate
Divisions: Faculty of Science and Engineering > School of Environmental Sciences
Depositing User: Symplectic Admin
Date Deposited: 20 Oct 2023 09:07
Last Modified: 20 Oct 2023 09:07
DOI: 10.1016/j.gca.2023.04.022
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3174372