Distortion of carbon isotope excursion in bulk soil organic matter during the Paleocene-Eocene thermal maximum

Research Article| September 01, 2016 Distortion of carbon isotope excursion in bulk soil organic matter during the Paleocene-Eocene thermal maximum Allison A. Baczynski; Allison A. Baczynski 1Department of Earth and Planetary Sciences, Northwestern University, Evanston, Illinois 60208, USA †Present address: Department of Geosciences, Pennsylvania State University, Deike Building, University Park, Pennsylvania 16802, USA; aab27@psu.edu. Search for other works by this author on: GSW Google Scholar Francesca A. McInerney; Francesca A. McInerney 1Department of Earth and Planetary Sciences, Northwestern University, Evanston, Illinois 60208, USA2Department of Earth Sciences and Sprigg Geobiology Centre, University of Adelaide, Adelaide, SA 5005, Australia Search for other works by this author on: GSW Google Scholar Scott L. Wing; Scott L. Wing 3Department of Paleobiology, Smithsonian Institution, NHB121, P.O. Box 37012, Washington, DC 20013-7012, USA Search for other works by this author on: GSW Google Scholar Mary J. Kraus; Mary J. Kraus 4Department of Geological Sciences, University of Colorado–Boulder, Boulder, Colorado 80309, USA Search for other works by this author on: GSW Google Scholar Paul E. Morse; Paul E. Morse 5Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611, USA6Department of Anthropology, University of Florida, Gainesville, Florida 32611, USA Search for other works by this author on: GSW Google Scholar Jonathan I. Bloch; Jonathan I. Bloch 5Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611, USA Search for other works by this author on: GSW Google Scholar Angela H. Chung; Angela H. Chung 7Department of Geosciences, Pennsylvania State University, Deike Building, University Park, Pennsylvania 16802, USA Search for other works by this author on: GSW Google Scholar Katherine H. Freeman Katherine H. Freeman 7Department of Geosciences, Pennsylvania State University, Deike Building, University Park, Pennsylvania 16802, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Allison A. Baczynski †Present address: Department of Geosciences, Pennsylvania State University, Deike Building, University Park, Pennsylvania 16802, USA; aab27@psu.edu. 1Department of Earth and Planetary Sciences, Northwestern University, Evanston, Illinois 60208, USA Francesca A. McInerney 1Department of Earth and Planetary Sciences, Northwestern University, Evanston, Illinois 60208, USA2Department of Earth Sciences and Sprigg Geobiology Centre, University of Adelaide, Adelaide, SA 5005, Australia Scott L. Wing 3Department of Paleobiology, Smithsonian Institution, NHB121, P.O. Box 37012, Washington, DC 20013-7012, USA Mary J. Kraus 4Department of Geological Sciences, University of Colorado–Boulder, Boulder, Colorado 80309, USA Paul E. Morse 5Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611, USA6Department of Anthropology, University of Florida, Gainesville, Florida 32611, USA Jonathan I. Bloch 5Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611, USA Angela H. Chung 7Department of Geosciences, Pennsylvania State University, Deike Building, University Park, Pennsylvania 16802, USA Katherine H. Freeman 7Department of Geosciences, Pennsylvania State University, Deike Building, University Park, Pennsylvania 16802, USA Publisher: Geological Society of America Received: 23 Jul 2015 Revision Received: 21 Jan 2016 Accepted: 14 Mar 2016 First Online: 02 Jun 2017 Online Issn: 1943-2674 Print Issn: 0016-7606 © 2016 Geological Society of America GSA Bulletin (2016) 128 (9-10): 1352–1366. https://doi.org/10.1130/B31389.1 Article history Received: 23 Jul 2015 Revision Received: 21 Jan 2016 Accepted: 14 Mar 2016 First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Allison A. Baczynski, Francesca A. McInerney, Scott L. Wing, Mary J. Kraus, Paul E. Morse, Jonathan I. Bloch, Angela H. Chung, Katherine H. Freeman; Distortion of carbon isotope excursion in bulk soil organic matter during the Paleocene-Eocene thermal maximum. GSA Bulletin 2016;; 128 (9-10): 1352–1366. doi: https://doi.org/10.1130/B31389.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Paleocene-Eocene thermal maximum was a period of abrupt, transient global warming, fueled by a large release of 13C-depleted carbon and marked globally by a negative carbon isotope excursion. While the carbon isotope excursion is often identified in the carbon isotope ratios of bulk soil organic matter (δ13Corg), these records can be biased by factors associated with production, degradation, and sources of sedimentary carbon input. To better understand these factors, we compared δ13Corg values from Paleocene-Eocene thermal maximum rocks in the southeastern Bighorn Basin, Wyoming, with those derived from leaf wax n-alkanes (δ13Cn-alk). While both δ13Cn-alk and δ13Corg records indicate an abrupt, negative shift in δ13C values, the carbon isotope excursions observed in bulk organic matter are smaller in magnitude and shorter in duration than those in n-alkanes. To explore these discrepancies, we modeled predicted total plant tissue carbon isotope (δ13CTT) curves from the δ13Cn-alk record using enrichment factors determined in modern C3 plants. Measured δ13Corg values are enriched in 13C relative to predicted δ13CTT, with greater enrichment during the Paleocene-Eocene thermal maximum than before or after. The greater 13C enrichment could reflect increased degradation of autochthonous organic matter, increased input of allochthonous fossil carbon enriched in 13C, or both. By comparing samples from organic-rich and organic-poor depositional environments, we infer that microbial degradation rates doubled during the Paleocene-Eocene thermal maximum, and we calculate that fossil carbon input increased ∼28%–63%. This approach to untangling the controls on the isotopic composition of bulk soil carbon is an important development that will inform not only future studies of global carbon cycle dynamics during the Paleocene-Eocene thermal maximum hyperthermal event, but also any study that seeks to correlate or estimate duration and magnitude of past events using soil organic carbon. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.