Palaeocene–Eocene Thermal Maximum prolonged by fossil carbon oxidation


A hallmark of the rapid and massive release of carbon during the Palaeocene–Eocene Thermal Maximum is the global negative carbon isotope excursion. The delayed recovery of the carbon isotope excursion, however, indicates that CO2 inputs continued well after the initial rapid onset, although there is no consensus about the source of this secondary carbon. Here we suggest this secondary input might have derived partly from the oxidation of remobilized sedimentary fossil carbon. We measured the biomarker indicators of thermal maturation in shelf records from the US Mid-Atlantic coast, constructed biomarker mixing models to constrain the amount of fossil carbon in US Mid-Atlantic and Tanzania coastal records, estimated the fossil carbon accumulation rate in coastal sediments and determined the range of global CO2 release from fossil carbon reservoirs. This work provides evidence for an order of magnitude increase in fossil carbon delivery to the oceans that began ~10–20 kyr after the event onset and demonstrates that the oxidation of remobilized fossil carbon released between 102 and 104 PgC as CO2 during the body of the Palaeocene–Eocene Thermal Maximum. The estimated mass is sufficient to have sustained the elevated atmospheric CO2 levels required by the prolonged global carbon isotope excursion. Even after considering uncertainties in the sedimentation rates, these results indicate that the enhanced erosion, mobilization and oxidation of ancient sedimentary carbon contributed to the delayed recovery of the climate system for many thousands of years.

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Fig. 1: Percent organic carbon and carbonate and organic isotope records plotted against depth at SDB and CamDor inner shelf sites.
Fig. 2: Biomarker thermal maturity ratios at SDB (top) and CamDor (bottom) demonstrate a source change during the PETM body.
Fig. 3: MARs of fossil C show an increase in fossil C delivery to sediments during the PETM body.
Fig. 4: Global estimates of fossil-C-derived CO2 release during the PETM body.

Data availability

The authors declare that the data supporting the findings of this study are available within the paper and its Supplementary Information files. Additional source data for Fig. 4 is available upon reasonable request.


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Funding for this study was provided by National Science Foundation grant no. CE-1416663. We acknowledge discussions with M. Robinson, K. Hantsoo and J. A. Grey. We are grateful to D. Walizer for analytical support. Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the US Government.

Author information




S.L.L., A.A.B., E.G.P. and J.R.V. carried out the organic isotope analyses, S.L.L. and A.A.B. carried out the biomarker analyses, S.L.L. interpreted the biomarker and isotope data, T.L.B. and J.C.Z. conducted and interpreted the carbonate isotope analyses, J.M.S.-T. determined the sedimentation rates, S.L.L. and E.A.H. designed the mixing model, K.H.F., J.C.Z., S.M.T., L.R.K., T.J.B. and A.A.B. contributed to major improvements within the models and data interpretation, S.L.L. wrote the paper, and all the authors contributed to interpreting the data and editing the paper. K.H.F. advised the direction of the research.

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Correspondence to Shelby L. Lyons.

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Lyons, S.L., Baczynski, A.A., Babila, T.L. et al. Palaeocene–Eocene Thermal Maximum prolonged by fossil carbon oxidation. Nature Geosci 12, 54–60 (2019).

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