The Role of Marine Diagenesis of Tephra in the Carbon Cycle

Hayley R. Manners1,2, Martin R. Palmer1, Tom M. Gernon1, Paul A. Sutton2, Martin R. Palmer1, Steve J. Rowland2 and Jim McManus3


School of Ocean and Earth Sciences, University of Southampton, National Oceanography Centre, Waterfront campus, Southampton SO14 3ZH, U.K.
2 Biogeochemistry Research Centre, University of Plymouth, Drake Circus, Plymouth PL4 8AA, U.K.
3 Department of Geosciences, University of Akron, Akron, OH, U.S.A.

Presented at: 27th International Meeting on Organic Geochemistry, Prague, Czech Republic, 13-18 September 2015.

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Brief Summary

Tephra and the carbon cycle. Volcanic material (tephra) is generally avoided in core-based climate studies or regarded as an inert diluent. Most subaerial volcanism, however, takes place close to the oceans so volcanic products are rapidly transported to the oceans. Such material is typically fine-grained and highly reactive. It rapidly undergoes a series of reactions with profound effects on the composition of solid and dissolved phases, including organic and inorganic carbon. This suggests tephra likely plays an important, hitherto unrecognised, role in carbon cycle dynamics (Figure 1).

Organic nitrogen (ON), tephra and the carbon cycle. ON plays an important role in N bioavailability and carbon sequestration within the entire biosphere, where it can remain sequestered for millions of years in sediments. The majority of ON is incorporated into compounds that are resistant to biological degradation and are thought to be preserved as amides. Here we present data that suggests organic matter (OM), and specifically amides, may be preferentially preserved by tephra, potentially through complexation with reactive iron. This may suggest that tephra plays a role in OM sequestration via mineral-OM interactions, representing a previously overlooked sink for CO2.

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