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Updated: Apr 25, 2026

Sampling and Pretreatment of Tooth Enamel Carbonate for Stable Carbon and Oxygen Isotope Analysis
Published on: August 15, 2018
Interpreting carbonate and organic carbon isotope covariance in the sedimentary record
Amanda M Oehlert1, Peter K Swart1
1Department of Marine Geosciences, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149, USA.
Abstract:
Many negative δ(13)C excursions in marine carbonates from the geological record are interpreted to record significant biogeochemical events in early Earth history. The assumption that no post-depositional processes can simultaneously alter carbonate and organic δ(13)C values towards more negative values is the cornerstone of this approach. However, the effects of post-depositional alteration on the relationship between carbonate and organic δ(13)C values have not been directly evaluated. Here we present paired carbonate and organic δ(13)C records that exhibit a coupled negative excursion resulting from multiple periods of meteoric alteration of the carbonate δ(13)C record, and consequent contributions of isotopically negative terrestrial organic matter to the sedimentary record. The possibility that carbonate and organic δ(13)C records can be simultaneously shifted towards lower δ(13)C values during periods of subaerial exposure may necessitate the reappraisal of some of the δ(13)C anomalies associated with noteworthy biogeochemical events throughout Earth history.
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