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Magnitude of the carbon isotope excursion at the Paleocene-Eocene thermal maximum: The role of plant community change

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dc.contributor.author Smith, Francesca A. en
dc.contributor.author Wing, Scott L. en
dc.contributor.author Freeman, Katherine H. en
dc.date.accessioned 2008-07-30T18:36:29Z
dc.date.available 2008-07-30T18:36:29Z
dc.date.issued 2007
dc.identifier.citation Smith, Francesca A., Wing, Scott L., and Freeman, Katherine H. 2007. "<a href="https://repository.si.edu/handle/10088/5992">Magnitude of the carbon isotope excursion at the Paleocene-Eocene thermal maximum: The role of plant community change</a>." <em>Earth and Planetary Science Letters</em>. 262 (1-2):50&ndash;65. <a href="https://doi.org/10.1016/j.epsl.2007.07.021">https://doi.org/10.1016/j.epsl.2007.07.021</a> en
dc.identifier.issn 0012-821X
dc.identifier.uri http://hdl.handle.net/10088/5992
dc.description.abstract Carbon-isotope measurements ([delta]13C) of leaf-wax n-alkanes from the Paleocene-Eocene Thermal Maximum (PETM) in the Bighorn Basin, Wyoming, reveal a negative carbon isotope excursion (CIE) of 4-5[per mille sign], which is 1-2[per mille sign] larger than that observed in marine carbonate [delta]13C records. Reconciling these records requires either that marine carbonates fail to record the full magnitude of the CIE or that the CIE in plants has been amplified relative to the marine. Amplification of the CIE has been proposed to result from an increase in available moisture that allowed terrestrial plants to increase 13C-discrimination during the PETM. Leaf physiognomy, paleopedology and hydrogen isotope ratios of leaf-wax lipids from the Bighorn Basin, however, all suggest that rather than a simple increase in available moisture, climate alternated between wet and dry during the PETM. Here we consider two other explanations and test them quantitatively with the carbon isotopic record of plant lipids. The &quot;marine modification&quot; hypothesis is that the marine carbonate record was modified by chemical changes at the PETM and that plant lipids record the true magnitude of the CIE. Using atmospheric CO2 [delta]13C values estimated from the lipid record, and equilibrium fractionation between CO2 and carbonate, we estimate the expected CIE for planktonic foraminifera to be 6[per mille sign]. Instead, the largest excursion observed is about 4[per mille sign]. No mechanism for altering marine carbonate by 2[per mille sign] has been identified and we thus reject this explanation. The &quot;plant community change&quot; hypothesis is that major changes in floral composition during the PETM amplified the CIE observed in n-alkanes by 1-2[per mille sign] relative to marine carbonate. This effect could have been caused by a rapid transition from a mixed angiosperm/conifer flora to a purely angiosperm flora. The plant community change hypothesis is consistent with both the magnitude and pattern of CIE amplification among the different n-alkanes, and with data from fossil plants. This hypothesis predicts that the magnitude and pattern of amplification of CIEs among different n-alkanes will vary regionally and systematically depending on the extent of the replacement of conifers by angiosperms during the PETM. en
dc.format.extent 793327 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US
dc.relation.ispartof Earth and Planetary Science Letters en
dc.title Magnitude of the carbon isotope excursion at the Paleocene-Eocene thermal maximum: The role of plant community change en
dc.type Journal Article en
dc.identifier.srbnumber 73180
dc.identifier.doi 10.1016/j.epsl.2007.07.021
rft.jtitle Earth and Planetary Science Letters
rft.volume 262
rft.issue 1-2
rft.spage 50
rft.epage 65
dc.description.SIUnit NMNH en
dc.description.SIUnit NH-Paleobiology en
dc.citation.spage 50
dc.citation.epage 65

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