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Two massive, rapid releases of carbon during the onset of the Palaeocene–Eocene thermal maximum


The Earth’s climate abruptly warmed by 5–8 °C during the Palaeocene–Eocene thermal maximum (PETM), about 55.5 million years ago1,2. This warming was associated with a massive addition of carbon to the ocean–atmosphere system, but estimates of the Earth system response to this perturbation are complicated by widely varying estimates of the duration of carbon release, which range from less than a year to tens of thousands of years. In addition the source of the carbon, and whether it was released as a single injection or in several pulses, remains the subject of debate2,3,4. Here we present a new high-resolution carbon isotope record from terrestrial deposits in the Bighorn Basin (Wyoming, USA) spanning the PETM, and interpret the record using a carbon-cycle box model of the ocean–atmosphere–biosphere system. Our record shows that the beginning of the PETM is characterized by not one but two distinct carbon release events, separated by a recovery to background values. To reproduce this pattern, our model requires two discrete pulses of carbon released directly to the atmosphere, at average rates exceeding 0.9 Pg C yr−1, with the first pulse lasting fewer than 2,000 years. We thus conclude that the PETM involved one or more reservoirs capable of repeated, catastrophic carbon release, and that rates of carbon release during the PETM were more similar to those associated with modern anthropogenic emissions5 than previously suggested3,4.

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Figure 1: Core and outcrop records of the PETM, Polecat Bench, Wyoming.
Figure 2: Detailed stratigraphy, PETM onset interval.
Figure 3: Carbon-cycle change during the PETM onset.


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This research used samples and/or data provided by the Bighorn Basin Coring Project (BBCP), and we thank the BBCP Science Team for participation in core collection, processing and sampling. We are grateful to H. Kuhlmann, H-J. Wallrabe-Adams, L. Schnieders, V. Lukies, A. Wülbers and W. Hale for their assistance throughout the project. We are indebted to R. Wilkens for providing knowledge and access to image analysis procedures. We thank V. Srinivasaraghavan, J. VanDeVelde, B. Theiling and S. Chakraborty for assistance with laboratory analyses. Funding for this research was provided by United States National Science Foundation grants 0958821, 0958622, 0958583 and 1261312, and by the Deutsche Forschungsgemeinschaft.

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G.J.B., B.J.M., P.D.G., W.C.C. and S.L.W. designed the study. B.J.M. carried out isotopic and petrographic analyses. U.R., T.W. and P.D.G. developed the composite depth scale, assembled the core images, and established the correlation to the outcrop level. M.J.K. developed the age model. A.S. collected data on carbonate nodule occurrence and morphology. G.J.B. developed and ran the carbon-cycle model simulations. G.J.B. and B.J.M. wrote the manuscript. All authors reviewed the manuscript and contributed to the Supplementary Information.

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Correspondence to Gabriel J. Bowen.

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Bowen, G., Maibauer, B., Kraus, M. et al. Two massive, rapid releases of carbon during the onset of the Palaeocene–Eocene thermal maximum. Nature Geosci 8, 44–47 (2015).

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