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  • 1
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    Distortion of carbon isotope excursion in bulk soil organic matter during the Paleocene-Eocene thermal maximum (2016)
    Geological Society of America (GSA)
    Details
    Publication Date: 2016-09-01
    Description: The Paleocene-Eocene thermal maximum was a period of abrupt, transient global warming, fueled by a large release of 13 C-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 ( 13 C org ), these records can be biased by factors associated with production, degradation, and sources of sedimentary carbon input. To better understand these factors, we compared 13 C org values from Paleocene-Eocene thermal maximum rocks in the southeastern Bighorn Basin, Wyoming, with those derived from leaf wax n -alkanes ( 13 C n -alk ). While both 13 C n -alk and 13 C org records indicate an abrupt, negative shift in 13 C 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 ( 13 C TT ) curves from the 13 C n -alk record using enrichment factors determined in modern C 3 plants. Measured 13 C org values are enriched in 13 C relative to predicted 13 C TT , with greater enrichment during the Paleocene-Eocene thermal maximum than before or after. The greater 13 C enrichment could reflect increased degradation of autochthonous organic matter, increased input of allochthonous fossil carbon enriched in 13 C, 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.
    Print ISSN: 0016-7606
    Electronic ISSN: 1943-2674
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 2
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    Late miocene atmospheric CO(2) concentrations and the expansion of C(4) grasses (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-08-07
    Description: The global expansion of C(4) grasslands in the late Miocene has been attributed to a large-scale decrease in atmospheric carbon dioxide (CO(2)) concentrations. This triggering mechanism is controversial, in part because of a lack of direct evidence for change in the partial pressure of CO(2) (pCO(2)) and because other factors are also important determinants in controlling plant-type distributions. Alkenone-based pCO(2) estimates for the late Miocene indicate that pCO(2) increased from 14 to 9 million years ago and stabilized at preindustrial values by 9 million years ago. The estimates presented here provide no evidence for major changes in pCO(2) during the late Miocene. Thus, C(4) plant expansion was likely driven by additional factors, possibly a tectonically related episode of enhanced low-latitude aridity or changes in seasonal precipitation patterns on a global scale (or both).〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pagani -- Freeman -- Arthur -- New York, N.Y. -- Science. 1999 Aug 6;285(5429):876-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geosciences, The Pennsylvania State University, University Park, PA 16872, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10436153" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Climate change as the dominant control on glacial-interglacial variations in C3 and C4 plant abundance (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-09-05
    Description: Although C4 plant expansions have been recognized in the late Miocene, identification of the underlying causes is complicated by the uncertainties associated with estimates of ancient precipitation, temperature, and partial pressure of atmospheric carbon dioxide (PCO2). Here we report the carbon isotopic compositions of leaf wax n-alkanes in lake sediment cores from two sites in Mesoamerica that have experienced contrasting moisture variations since the last glacial maximum. Opposite isotopic trends obtained from these two sites indicate that regional climate exerts a strong control on the relative abundance of C3 and C4 plants and that in the absence of favorable moisture and temperature conditions, low PCO2 alone is insufficient to drive an expansion of C4 plants.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Huang, Y -- Street-Perrott, F A -- Metcalfe, S E -- Brenner, M -- Moreland, M -- Freeman, K H -- New York, N.Y. -- Science. 2001 Aug 31;293(5535):1647-51.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geological Sciences, Brown University, Providence, RI 02912, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11533488" target="_blank"〉PubMed〈/a〉
    Keywords: Alkanes/analysis ; Atmosphere ; Carbon Dioxide ; Carbon Isotopes/analysis ; *Climate ; *Ecosystem ; Fossils ; Fresh Water ; Geologic Sediments/*chemistry ; Guatemala ; Mexico ; Photosynthesis ; *Plant Development ; Plant Leaves/chemistry ; Plants/metabolism ; Poaceae/*growth & development/metabolism ; Pollen ; Rain ; Seasons ; Temperature ; Trees/growth & development ; Weather
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Journal club. A biogeochemist ponders muddy molecules and past climates (2009)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2009-12-17
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Freeman, Katherine H -- England -- Nature. 2009 Dec 10;462(7274):701. doi: 10.1038/462701e.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Pennsylvania State University, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20010651" target="_blank"〉PubMed〈/a〉
    Keywords: *Climate ; Climate Change ; *Fossils ; Geologic Sediments/*chemistry ; Membrane Lipids/*analysis ; Seawater/chemistry ; Temperature
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 5
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    Transient floral change and rapid global warming at the Paleocene-Eocene boundary (2005)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2005-11-15
    Description: Rapid global warming of 5 degrees to 10 degrees C during the Paleocene-Eocene Thermal Maximum (PETM) coincided with major turnover in vertebrate faunas, but previous studies have found little floral change. Plant fossils discovered in Wyoming, United States, show that PETM floras were a mixture of native and migrant lineages and that plant range shifts were large and rapid (occurring within 10,000 years). Floral composition and leaf shape and size suggest that climate warmed by approximately 5 degrees C during the PETM and that precipitation was low early in the event and increased later. Floral response to warming and/or increased atmospheric CO2 during the PETM was comparable in rate and magnitude to that seen in postglacial floras and to the predicted effects of anthropogenic carbon release and climate change on future vegetation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wing, Scott L -- Harrington, Guy J -- Smith, Francesca A -- Bloch, Jonathan I -- Boyer, Douglas M -- Freeman, Katherine H -- New York, N.Y. -- Science. 2005 Nov 11;310(5750):993-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Paleobiology, Smithsonian Museum of Natural History, 10th Street and Constitution Avenue, NW, Washington, DC 20560, USA. wings@si.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16284173" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biodiversity ; Carbon Isotopes/analysis ; *Climate ; *Ecosystem ; *Fossils ; Geologic Sediments ; *Greenhouse Effect ; Oxygen Isotopes/analysis ; Plant Development ; Plant Leaves/anatomy & histology ; *Plants/anatomy & histology/classification ; Rain ; Temperature ; Time Factors ; Wyoming
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
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    Marked decline in atmospheric carbon dioxide concentrations during the Paleogene (2005)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2005-06-18
    Description: The relation between the partial pressure of atmospheric carbon dioxide (pCO2) and Paleogene climate is poorly resolved. We used stable carbon isotopic values of di-unsaturated alkenones extracted from deep sea cores to reconstruct pCO2 from the middle Eocene to the late Oligocene (approximately 45 to 25 million years ago). Our results demonstrate that pCO2 ranged between 1000 to 1500 parts per million by volume in the middle to late Eocene, then decreased in several steps during the Oligocene, and reached modern levels by the latest Oligocene. The fall in pCO2 likely allowed for a critical expansion of ice sheets on Antarctica and promoted conditions that forced the onset of terrestrial C4 photosynthesis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pagani, Mark -- Zachos, James C -- Freeman, Katherine H -- Tipple, Brett -- Bohaty, Stephen -- New York, N.Y. -- Science. 2005 Jul 22;309(5734):600-3. Epub 2005 Jun 16.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geology and Geophysics, Yale University, 210 Whitney Avenue, New Haven, CT 06511, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15961630" target="_blank"〉PubMed〈/a〉
    Keywords: *Atmosphere ; Carbon Dioxide/*analysis/metabolism ; Carbon Isotopes/analysis ; *Climate ; Ecosystem ; Eukaryota/cytology/growth & development/metabolism ; Ice ; *Photosynthesis ; Phytoplankton/cytology/growth & development/metabolism ; Plant Development ; Plants/metabolism ; Poaceae/growth & development/metabolism ; Time
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    Earth science: controls on isotopic gradients in rain (2014)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2014-12-05
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Freeman, Katherine H -- England -- Nature. 2014 Dec 4;516(7529):41-2. doi: 10.1038/516041a.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16803, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25471876" target="_blank"〉PubMed〈/a〉
    Keywords: Hydrogen/analysis ; Models, Theoretical ; Oxygen Isotopes/analysis ; Rain/*chemistry ; *Water Cycle
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 8
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    Geoffrey Eglinton (1927-2016) (2016)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2016-04-30
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Freeman, Katherine H -- England -- Nature. 2016 Apr 21;532(7599):314.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/27127818" target="_blank"〉PubMed〈/a〉
    Keywords: Chemistry, Organic/*history ; Chromatography, Gas/history ; Extraterrestrial Environment/chemistry ; Fossils ; Geologic Sediments/chemistry ; Geology/*history ; Great Britain ; History, 20th Century ; History, 21st Century ; Moon ; Waxes/chemistry
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 9
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    Late Archean rise of aerobic microbial ecosystems (2006)
    National Academy of Sciences
    Details
    Publication Date: 2006-10-16
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 10
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    Clarifying the influence of water availability and plant types on carbon isotope discrimination by C3 plants (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-04-07
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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