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Edited* by Wallace S. Broecker, Columbia University, Palisades, NY, and approved August 5, 2013 (received for review May 14, 2013)
Significance
Calcium carbonate and carbon isotope records from the rhythmically bedded Marlboro Clay, deposited during the onset of the PETM CIE, show that the massive release of isotopically light carbon was instantaneous, providing important constraints for the magnitude of carbon released and potential mechanisms.
Abstract
The Paleocene/Eocene thermal maximum (PETM) and associated carbon isotope excursion (CIE) are often touted as the best geologic analog for the current anthropogenic rise in pCO2. However, a causal mechanism for the PETM CIE remains unidentified because of large uncertainties in the duration of the CIE’s onset. Here, we report on a sequence of rhythmic sedimentary couplets comprising the Paleocene/Eocene Marlboro Clay (Salisbury Embayment). These couplets have corresponding δ18O cycles that imply a climatic origin. Seasonal insolation is the only regular climate cycle that can plausibly account for δ18O amplitudes and layer counts. High-resolution stable isotope records show 3.5‰ δ13C decrease over 13 couplets defining the CIE onset, which requires a large, instantaneous release of 13C-depleted carbon. During the CIE, a clear δ13C gradient developed on the shelf with the largest excursions in shallowest waters, indicating atmospheric δ13C decreased by ∼20‰. Our observations and revised release rate are consistent with an atmospheric perturbation of 3,000-gigatons of carbon (GtC).
Footnotes
- ↵1To whom correspondence should be addressed. E-mail: jdwright{at}rci.rutgers.edu.
Author contributions: J.D.W. and M.F.S. designed research, performed research, analyzed data, and wrote the paper.
The authors declare no conflict of interest.
↵*This Direct Submission article had a prearranged editor.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1309188110/-/DCSupplemental.
Rapid release of carbon at the PETM
Article Classifications
- Physical Sciences
- Earth, Atmospheric, and Planetary Sciences
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- Article
- Abstract
- Temporal Origin of the Couplets Within the Marlboro Clay
- Timing of the Onset of the CIE from High-Resolution Stable Isotopes in Millville
- Surface Water CO2(aq) Concentrations and Carbon Isotopic Equilibrium
- Reconciling the Marlboro Clay and Deep Ocean Chronologies
- Atmospheric Response to PETM CIE
- Implications for the Rate of Carbon Release and Sequence of Events at the PETM
- Acknowledgments
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