Links to Exploration step
Le document en format XML
<record><TEI><teiHeader><fileDesc><titleStmt><title xml:lang="en">Pristine Early Eocene Wood Buried Deeply in Kimberlite from Northern Canada</title><author><name sortKey="Wolfe, Alexander P" sort="Wolfe, Alexander P" uniqKey="Wolfe A" first="Alexander P." last="Wolfe">Alexander P. Wolfe</name><affiliation><nlm:aff id="aff1"><addr-line>Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Canada</addr-line></nlm:aff></affiliation></author><author><name sortKey="Csank, Adam Z" sort="Csank, Adam Z" uniqKey="Csank A" first="Adam Z." last="Csank">Adam Z. Csank</name><affiliation><nlm:aff id="aff2"><addr-line>Environment and Natural Resources Institute, University of Alaska, Anchorage, Alaska, United States of America</addr-line></nlm:aff></affiliation></author><author><name sortKey="Reyes, Alberto V" sort="Reyes, Alberto V" uniqKey="Reyes A" first="Alberto V." last="Reyes">Alberto V. Reyes</name><affiliation><nlm:aff id="aff3"><addr-line>Department of Geoscience, University of Wisconsin, Madison, Wisconsin, United States of America</addr-line></nlm:aff></affiliation></author><author><name sortKey="Mckellar, Ryan C" sort="Mckellar, Ryan C" uniqKey="Mckellar R" first="Ryan C." last="Mckellar">Ryan C. Mckellar</name><affiliation><nlm:aff id="aff1"><addr-line>Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Canada</addr-line></nlm:aff></affiliation></author><author><name sortKey="Tappert, Ralf" sort="Tappert, Ralf" uniqKey="Tappert R" first="Ralf" last="Tappert">Ralf Tappert</name><affiliation><nlm:aff id="aff4"><addr-line>Institute of Mineralogy and Petrography, University of Innsbruck, Innsbruck, Austria</addr-line></nlm:aff></affiliation></author><author><name sortKey="Muehlenbachs, Karlis" sort="Muehlenbachs, Karlis" uniqKey="Muehlenbachs K" first="Karlis" last="Muehlenbachs">Karlis Muehlenbachs</name><affiliation><nlm:aff id="aff1"><addr-line>Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Canada</addr-line></nlm:aff></affiliation></author></titleStmt><publicationStmt><idno type="wicri:source">PMC</idno><idno type="pmid">23029080</idno><idno type="pmc">3446892</idno><idno type="url">http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3446892</idno><idno type="RBID">PMC:3446892</idno><idno type="doi">10.1371/journal.pone.0045537</idno><date when="2012">2012</date><idno type="wicri:Area/Pmc/Corpus">000448</idno><idno type="wicri:explorRef" wicri:stream="Pmc" wicri:step="Corpus" wicri:corpus="PMC">000448</idno></publicationStmt><sourceDesc><biblStruct><analytic><title xml:lang="en" level="a" type="main">Pristine Early Eocene Wood Buried Deeply in Kimberlite from Northern Canada</title><author><name sortKey="Wolfe, Alexander P" sort="Wolfe, Alexander P" uniqKey="Wolfe A" first="Alexander P." last="Wolfe">Alexander P. Wolfe</name><affiliation><nlm:aff id="aff1"><addr-line>Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Canada</addr-line></nlm:aff></affiliation></author><author><name sortKey="Csank, Adam Z" sort="Csank, Adam Z" uniqKey="Csank A" first="Adam Z." last="Csank">Adam Z. Csank</name><affiliation><nlm:aff id="aff2"><addr-line>Environment and Natural Resources Institute, University of Alaska, Anchorage, Alaska, United States of America</addr-line></nlm:aff></affiliation></author><author><name sortKey="Reyes, Alberto V" sort="Reyes, Alberto V" uniqKey="Reyes A" first="Alberto V." last="Reyes">Alberto V. Reyes</name><affiliation><nlm:aff id="aff3"><addr-line>Department of Geoscience, University of Wisconsin, Madison, Wisconsin, United States of America</addr-line></nlm:aff></affiliation></author><author><name sortKey="Mckellar, Ryan C" sort="Mckellar, Ryan C" uniqKey="Mckellar R" first="Ryan C." last="Mckellar">Ryan C. Mckellar</name><affiliation><nlm:aff id="aff1"><addr-line>Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Canada</addr-line></nlm:aff></affiliation></author><author><name sortKey="Tappert, Ralf" sort="Tappert, Ralf" uniqKey="Tappert R" first="Ralf" last="Tappert">Ralf Tappert</name><affiliation><nlm:aff id="aff4"><addr-line>Institute of Mineralogy and Petrography, University of Innsbruck, Innsbruck, Austria</addr-line></nlm:aff></affiliation></author><author><name sortKey="Muehlenbachs, Karlis" sort="Muehlenbachs, Karlis" uniqKey="Muehlenbachs K" first="Karlis" last="Muehlenbachs">Karlis Muehlenbachs</name><affiliation><nlm:aff id="aff1"><addr-line>Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Canada</addr-line></nlm:aff></affiliation></author></analytic><series><title level="j">PLoS ONE</title><idno type="eISSN">1932-6203</idno><imprint><date when="2012">2012</date></imprint></series></biblStruct></sourceDesc></fileDesc><profileDesc><textClass></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en"><p>We report exceptional preservation of fossil wood buried deeply in a kimberlite pipe that intruded northwestern Canada’s Slave Province 53.3±0.6 million years ago (Ma), revealed during excavation of diamond source rock. The wood originated from forest surrounding the eruption zone and collapsed into the diatreme before resettling in volcaniclastic kimberlite to depths >300 m, where it was mummified in a sterile environment. Anatomy of the unpermineralized wood permits conclusive identification to the genus <italic>Metasequoia</italic> (Cupressaceae). The wood yields genuine cellulose and occluded amber, both of which have been characterized spectroscopically and isotopically. From cellulose δ<sup>18</sup>O and δ<sup>2</sup>H measurements, we infer that Early Eocene paleoclimates in the western Canadian subarctic were 12–17°C warmer and four times wetter than present. Canadian kimberlites offer Lagerstätte-quality preservation of wood from a region with limited alternate sources of paleobotanical information.</p></div></front><back><div1 type="bibliography"><listBibl><biblStruct><analytic><author><name sortKey="Wilson, L" uniqKey="Wilson L">L Wilson</name></author><author><name sortKey="Head, Jw" uniqKey="Head J">JW Head</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Edwards, B" uniqKey="Edwards B">B Edwards</name></author><author><name sortKey="Howkins, B" uniqKey="Howkins B">B Howkins</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Smith, Rmh" uniqKey="Smith R">RMH Smith</name></author></analytic></biblStruct><biblStruct></biblStruct><biblStruct><analytic><author><name sortKey="Cookenboo, Ho" uniqKey="Cookenboo H">HO Cookenboo</name></author><author><name sortKey="Orchard, Mj" uniqKey="Orchard M">MJ Orchard</name></author><author><name sortKey="Daoud, Dk" uniqKey="Daoud D">DK Daoud</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Wolfe, Ap" uniqKey="Wolfe A">AP Wolfe</name></author><author><name sortKey="Siver, Pa" uniqKey="Siver P">PA Siver</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Doria, G" uniqKey="Doria G">G Doria</name></author><author><name sortKey="Royer, Dl" uniqKey="Royer D">DL Royer</name></author><author><name sortKey="Wolfe, Ap" uniqKey="Wolfe A">AP Wolfe</name></author><author><name sortKey="Fox, A" uniqKey="Fox A">A Fox</name></author><author><name sortKey="Westgate, Ja" uniqKey="Westgate J">JA Westgate</name></author><author><name sortKey="Beerling, Dj" uniqKey="Beerling D">DJ Beerling</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Nowicki, T" uniqKey="Nowicki T">T Nowicki</name></author><author><name sortKey="Crawford, B" uniqKey="Crawford B">B Crawford</name></author><author><name sortKey="Dyck, D" uniqKey="Dyck D">D Dyck</name></author><author><name sortKey="Carlson, J" uniqKey="Carlson J">J Carlson</name></author><author><name sortKey="Mcelroy, R" uniqKey="Mcelroy R">R McElroy</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Creaser, Ra" uniqKey="Creaser R">RA Creaser</name></author><author><name sortKey="Grutter, Hs" uniqKey="Grutter H">HS Grütter</name></author><author><name sortKey="Carlson, J" uniqKey="Carlson J">J Carlson</name></author><author><name sortKey="Crawford, B" uniqKey="Crawford B">B Crawford</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Kr Usel, R" uniqKey="Kr Usel R">R Kräusel</name></author></analytic></biblStruct><biblStruct></biblStruct><biblStruct><analytic><author><name sortKey="Meijer, Jjf" uniqKey="Meijer J">JJF Meijer</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Visscher, Ge" uniqKey="Visscher G">GE Visscher</name></author><author><name sortKey="Jagels, R" uniqKey="Jagels R">R Jagels</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Sunderlin, D" uniqKey="Sunderlin D">D Sunderlin</name></author><author><name sortKey="Loope, G" uniqKey="Loope G">G Loope</name></author><author><name sortKey="Parker, Ne" uniqKey="Parker N">NE Parker</name></author><author><name sortKey="Williams, Cj" uniqKey="Williams C">CJ Williams</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Richter, Sl" uniqKey="Richter S">SL Richter</name></author><author><name sortKey="Johnson, Ah" uniqKey="Johnson A">AH Johnson</name></author><author><name sortKey="Dranoff, Mm" uniqKey="Dranoff M">MM Dranoff</name></author><author><name sortKey="Lepage, Ba" uniqKey="Lepage B">BA LePage</name></author><author><name sortKey="Williams, Cj" uniqKey="Williams C">CJ Williams</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Rhoads, Ca" uniqKey="Rhoads C">CA Rhoads</name></author><author><name sortKey="Painter, Pc" uniqKey="Painter P">PC Painter</name></author><author><name sortKey="Given, Ph" uniqKey="Given P">PH Given</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Terinte, N" uniqKey="Terinte N">N Terinte</name></author><author><name sortKey="Ibbett, R" uniqKey="Ibbett R">R Ibbett</name></author><author><name sortKey="Schuster, Kc" uniqKey="Schuster K">KC Schuster</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Anderson, Kb" uniqKey="Anderson K">KB Anderson</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Tappert, R" uniqKey="Tappert R">R Tappert</name></author><author><name sortKey="Wolfe, Ap" uniqKey="Wolfe A">AP Wolfe</name></author><author><name sortKey="Mckellar, Rc" uniqKey="Mckellar R">RC McKellar</name></author><author><name sortKey="Tappert, M" uniqKey="Tappert M">M Tappert</name></author><author><name sortKey="Muehlenbachs, K" uniqKey="Muehlenbachs K">K Muehlenbachs</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Otto, A" uniqKey="Otto A">A Otto</name></author><author><name sortKey="Simoneit, Brt" uniqKey="Simoneit B">BRT Simoneit</name></author><author><name sortKey="Wilde, V" uniqKey="Wilde V">V Wilde</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Hudgins, Jw" uniqKey="Hudgins J">JW Hudgins</name></author><author><name sortKey="Krekling, T" uniqKey="Krekling T">T Krekling</name></author><author><name sortKey="Franceschi, Vr" uniqKey="Franceschi V">VR Franceschi</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Kavanagh, Jl" uniqKey="Kavanagh J">JL Kavanagh</name></author><author><name sortKey="Sparks, Rs" uniqKey="Sparks R">RS Sparks</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Stasiuk, Ld" uniqKey="Stasiuk L">LD Stasiuk</name></author><author><name sortKey="Lockhart, Gd" uniqKey="Lockhart G">GD Lockhart</name></author><author><name sortKey="Nassichuk, Ww" uniqKey="Nassichuk W">WW Nassichuk</name></author><author><name sortKey="Carlson, Ja" uniqKey="Carlson J">JA Carlson</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Epstein, S" uniqKey="Epstein S">S Epstein</name></author><author><name sortKey="Thompson, P" uniqKey="Thompson P">P Thompson</name></author><author><name sortKey="Yapp, Cj" uniqKey="Yapp C">CJ Yapp</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="West, Jb" uniqKey="West J">JB West</name></author><author><name sortKey="Sobek, A" uniqKey="Sobek A">A Sobek</name></author><author><name sortKey="Ehleringer, Jr" uniqKey="Ehleringer J">JR Ehleringer</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Pagani, M" uniqKey="Pagani M">M Pagani</name></author><author><name sortKey="Pedentchouk, N" uniqKey="Pedentchouk N">N Pedentchouk</name></author><author><name sortKey="Huber, M" uniqKey="Huber M">M Huber</name></author><author><name sortKey="Sluijs, A" uniqKey="Sluijs A">A Sluijs</name></author><author><name sortKey="Schouten, S" uniqKey="Schouten S">S Schouten</name></author></analytic></biblStruct><biblStruct></biblStruct><biblStruct><analytic><author><name sortKey="Mckellar, Rc" uniqKey="Mckellar R">RC McKellar</name></author><author><name sortKey="Wolfe, Ap" uniqKey="Wolfe A">AP Wolfe</name></author><author><name sortKey="Tappert, R" uniqKey="Tappert R">R Tappert</name></author><author><name sortKey="Muehlenbachs, K" uniqKey="Muehlenbachs K">K Muehlenbachs</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Chikaraishi, Y" uniqKey="Chikaraishi Y">Y Chikaraishi</name></author><author><name sortKey="Naraoka, H" uniqKey="Naraoka H">H Naraoka</name></author><author><name sortKey="Poulson, Sr" uniqKey="Poulson S">SR Poulson</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Gonzalez, G" uniqKey="Gonzalez G">G Gonzalez</name></author><author><name sortKey="Tappert, R" uniqKey="Tappert R">R Tappert</name></author><author><name sortKey="Wolfe, Ap" uniqKey="Wolfe A">AP Wolfe</name></author><author><name sortKey="Muehlenbachs, K" uniqKey="Muehlenbachs K">K Muehlenbachs</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Jahren, Ah" uniqKey="Jahren A">AH Jahren</name></author><author><name sortKey="Sternberg, Lsl" uniqKey="Sternberg L">LSL Sternberg</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Lipp, J" uniqKey="Lipp J">J Lipp</name></author><author><name sortKey="Trimborn, P" uniqKey="Trimborn P">P Trimborn</name></author><author><name sortKey="Fritz, P" uniqKey="Fritz P">P Fritz</name></author><author><name sortKey="Moser, H" uniqKey="Moser H">H Moser</name></author><author><name sortKey="Becker, B" uniqKey="Becker B">B Becker</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Jahren, Ah" uniqKey="Jahren A">AH Jahren</name></author><author><name sortKey="Sternberg, Lsl" uniqKey="Sternberg L">LSL Sternberg</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Eberle, Jj" uniqKey="Eberle J">JJ Eberle</name></author><author><name sortKey="Fricke, Hc" uniqKey="Fricke H">HC Fricke</name></author><author><name sortKey="Humphrey, Jd" uniqKey="Humphrey J">JD Humphrey</name></author><author><name sortKey="Hackett, L" uniqKey="Hackett L">L Hackett</name></author><author><name sortKey="Newbrey, Mg" uniqKey="Newbrey M">MG Newbrey</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Roden, Js" uniqKey="Roden J">JS Roden</name></author><author><name sortKey="Lin, G" uniqKey="Lin G">G Lin</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Anderson, Wt" uniqKey="Anderson W">WT Anderson</name></author><author><name sortKey="Bernasconi, Sm" uniqKey="Bernasconi S">SM Bernasconi</name></author><author><name sortKey="Mckenzie, Ja" uniqKey="Mckenzie J">JA McKenzie</name></author><author><name sortKey="Saurer, M" uniqKey="Saurer M">M Saurer</name></author><author><name sortKey="Schweingruber, F" uniqKey="Schweingruber F">F Schweingruber</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Fricke, Hc" uniqKey="Fricke H">HC Fricke</name></author><author><name sortKey="Wing, Sl" uniqKey="Wing S">SL Wing</name></author></analytic></biblStruct><biblStruct></biblStruct><biblStruct></biblStruct><biblStruct><analytic><author><name sortKey="Sluijs, A" uniqKey="Sluijs A">A Sluijs</name></author><author><name sortKey="Schouten, S" uniqKey="Schouten S">S Schouten</name></author><author><name sortKey="Donders, Th" uniqKey="Donders T">TH Donders</name></author><author><name sortKey="Schoon, P" uniqKey="Schoon P">P Schoon</name></author><author><name sortKey="Rohl, U" uniqKey="Rohl U">U Röhl</name></author></analytic></biblStruct><biblStruct></biblStruct><biblStruct><analytic><author><name sortKey="Ault, Ak" uniqKey="Ault A">AK Ault</name></author><author><name sortKey="Flowers, Rm" uniqKey="Flowers R">RM Flowers</name></author><author><name sortKey="Bowring, Sa" uniqKey="Bowring S">SA Bowring</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Zachos, J" uniqKey="Zachos J">J Zachos</name></author><author><name sortKey="Pagani, M" uniqKey="Pagani M">M Pagani</name></author><author><name sortKey="Sloan, L" uniqKey="Sloan L">L Sloan</name></author><author><name sortKey="Thomas, E" uniqKey="Thomas E">E Thomas</name></author><author><name sortKey="Billups, K" uniqKey="Billups K">K Billups</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Gaudinski, Jb" uniqKey="Gaudinski J">JB Gaudinski</name></author><author><name sortKey="Dawson, Te" uniqKey="Dawson T">TE Dawson</name></author><author><name sortKey="Quideau, S" uniqKey="Quideau S">S Quideau</name></author><author><name sortKey="Schuur, Eag" uniqKey="Schuur E">EAG Schuur</name></author><author><name sortKey="Roden, Js" uniqKey="Roden J">JS Roden</name></author></analytic></biblStruct><biblStruct></biblStruct></listBibl></div1></back></TEI><pmc article-type="research-article"><pmc-dir>properties open_access</pmc-dir>
<front><journal-meta><journal-id journal-id-type="nlm-ta">PLoS One</journal-id><journal-id journal-id-type="iso-abbrev">PLoS ONE</journal-id><journal-id journal-id-type="publisher-id">plos</journal-id><journal-id journal-id-type="pmc">plosone</journal-id><journal-title-group><journal-title>PLoS ONE</journal-title></journal-title-group><issn pub-type="epub">1932-6203</issn><publisher><publisher-name>Public Library of Science</publisher-name><publisher-loc>San Francisco, USA</publisher-loc></publisher></journal-meta><article-meta><article-id pub-id-type="pmid">23029080</article-id><article-id pub-id-type="pmc">3446892</article-id><article-id pub-id-type="publisher-id">PONE-D-12-00237</article-id><article-id pub-id-type="doi">10.1371/journal.pone.0045537</article-id><article-categories><subj-group subj-group-type="heading"><subject>Research Article</subject></subj-group><subj-group subj-group-type="Discipline-v2"><subject>Biology</subject><subj-group><subject>Ecology</subject><subj-group><subject>Paleoecology</subject></subj-group></subj-group><subj-group><subject>Paleontology</subject><subj-group><subject>Paleobotany</subject><subject>Paleoclimatology</subject></subj-group></subj-group><subj-group><subject>Plant Science</subject><subj-group><subject>Plant Ecology</subject><subj-group><subject>Plant-Environment Interactions</subject></subj-group></subj-group></subj-group></subj-group><subj-group subj-group-type="Discipline-v2"><subject>Chemistry</subject><subj-group><subject>Geochemistry</subject><subj-group><subject>Biogeochemistry</subject></subj-group></subj-group></subj-group><subj-group subj-group-type="Discipline-v2"><subject>Earth Sciences</subject><subj-group><subject>Geochemistry</subject><subj-group><subject>Biogeochemistry</subject></subj-group></subj-group></subj-group></article-categories><title-group><article-title>Pristine Early Eocene Wood Buried Deeply in Kimberlite from Northern Canada</article-title><alt-title alt-title-type="running-head">Pristine Early Eocene Fossil Wood</alt-title></title-group><contrib-group><contrib contrib-type="author"><name><surname>Wolfe</surname><given-names>Alexander P.</given-names></name><xref ref-type="aff" rid="aff1"><sup>1</sup></xref><xref ref-type="corresp" rid="cor1"><sup>*</sup></xref></contrib><contrib contrib-type="author"><name><surname>Csank</surname><given-names>Adam Z.</given-names></name><xref ref-type="aff" rid="aff2"><sup>2</sup></xref></contrib><contrib contrib-type="author"><name><surname>Reyes</surname><given-names>Alberto V.</given-names></name><xref ref-type="aff" rid="aff3"><sup>3</sup></xref></contrib><contrib contrib-type="author"><name><surname>McKellar</surname><given-names>Ryan C.</given-names></name><xref ref-type="aff" rid="aff1"><sup>1</sup></xref></contrib><contrib contrib-type="author"><name><surname>Tappert</surname><given-names>Ralf</given-names></name><xref ref-type="aff" rid="aff4"><sup>4</sup></xref></contrib><contrib contrib-type="author"><name><surname>Muehlenbachs</surname><given-names>Karlis</given-names></name><xref ref-type="aff" rid="aff1"><sup>1</sup></xref></contrib></contrib-group><aff id="aff1"><label>1</label><addr-line>Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Canada</addr-line></aff><aff id="aff2"><label>2</label><addr-line>Environment and Natural Resources Institute, University of Alaska, Anchorage, Alaska, United States of America</addr-line></aff><aff id="aff3"><label>3</label><addr-line>Department of Geoscience, University of Wisconsin, Madison, Wisconsin, United States of America</addr-line></aff><aff id="aff4"><label>4</label><addr-line>Institute of Mineralogy and Petrography, University of Innsbruck, Innsbruck, Austria</addr-line></aff><contrib-group><contrib contrib-type="editor"><name><surname>Newsom</surname><given-names>Lee A.</given-names></name><role>Editor</role><xref ref-type="aff" rid="edit1"></xref></contrib></contrib-group><aff id="edit1"><addr-line>The Pennsylvania State University, United States of America</addr-line></aff><author-notes><corresp id="cor1">* E-mail: <email>awolfe@ualberta.ca</email></corresp><fn fn-type="conflict"><p><bold>Competing Interests: </bold>The authors have declared that no competing interests exist.</p></fn><fn fn-type="con"><p>Conceived and designed the experiments: APW AZC AVR RCM RT KM. Performed the experiments: APW AZC AVR RCM RT KM. Analyzed the data: APW AZC AVR RCM RT KM. Contributed reagents/materials/analysis tools: APW AZC AVR RCM RT KM. Wrote the paper: APW AZC AVR RCM RT KM. Microscopy: APW. Wood anatomy: ACZ. Cellulose purification: ACZ AVR. FTIR spectroscopy: RCM RT. Isotopic measurements: ACZ AVR RCM RT KM.</p></fn></author-notes><pub-date pub-type="collection"><year>2012</year></pub-date><pub-date pub-type="epub"><day>19</day><month>9</month><year>2012</year></pub-date><volume>7</volume><issue>9</issue><elocation-id>e45537</elocation-id><history><date date-type="received"><day>16</day><month>12</month><year>2011</year></date><date date-type="accepted"><day>23</day><month>8</month><year>2012</year></date></history><permissions><copyright-year>2012</copyright-year><copyright-holder>Wolfe et al</copyright-holder><license><license-p>This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.</license-p></license></permissions><abstract><p>We report exceptional preservation of fossil wood buried deeply in a kimberlite pipe that intruded northwestern Canada’s Slave Province 53.3±0.6 million years ago (Ma), revealed during excavation of diamond source rock. The wood originated from forest surrounding the eruption zone and collapsed into the diatreme before resettling in volcaniclastic kimberlite to depths >300 m, where it was mummified in a sterile environment. Anatomy of the unpermineralized wood permits conclusive identification to the genus <italic>Metasequoia</italic> (Cupressaceae). The wood yields genuine cellulose and occluded amber, both of which have been characterized spectroscopically and isotopically. From cellulose δ<sup>18</sup>O and δ<sup>2</sup>H measurements, we infer that Early Eocene paleoclimates in the western Canadian subarctic were 12–17°C warmer and four times wetter than present. Canadian kimberlites offer Lagerstätte-quality preservation of wood from a region with limited alternate sources of paleobotanical information.</p></abstract><funding-group><funding-statement>Funding was provided by the Natural Sciences and Engineering Research Council of Canada. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.</funding-statement></funding-group><counts><page-count count="8"></page-count></counts></article-meta></front><body><sec id="s1"><title>Introduction</title><p>Kimberlites are volatile-rich volcanic systems that ascend from the mantle episodically in Earth history as explosive phreatomagmatic events <xref ref-type="bibr" rid="pone.0045537-Wilson1">[1]</xref>. Fossils associated with kimberlites have been recognized for decades <xref ref-type="bibr" rid="pone.0045537-Edwards1">[2]</xref>, <xref ref-type="bibr" rid="pone.0045537-Smith1">[3]</xref>. Two modes of preservation are possible: (1) collapse or entrainment into the diatreme at the time of emplacement, resulting in the emtombment of fossiliferous xenoliths within the kimberlite body; and (2) accumulation in the crater following magmatism (kimberlite maar sedimentation). Both preservation types occur in kimberlite pipes of northwestern Canada’s Slave Province <xref ref-type="bibr" rid="pone.0045537-Nassichuk1">[4]</xref>–<xref ref-type="bibr" rid="pone.0045537-Doria1">[7]</xref>. Although abundant wood has been recovered at depth from the Panda pipe (64.73°N, 110.59°W; <xref ref-type="fig" rid="pone-0045537-g001">Fig. 1</xref>) during mining of the diamondiferous ore body on BHP Billiton’s Ekati property, these remarkable botanical fossils have not yet been described in detail. We report here on the preservation and identification of unpermineralized wood recovered from the Panda kimberlite, and present an array of stable isotopic measurements that are used to derive a provisional reconstruction of regional paleoclimate during the Early Eocene.</p><fig id="pone-0045537-g001" orientation="portrait" position="float"><object-id pub-id-type="doi">10.1371/journal.pone.0045537.g001</object-id><label>Figure 1</label><caption><title>Study site and fossil wood from the Panda kimberlite pipe.</title><p>A. Location of the Ekati diamond mine. B. Situation of the Panda kimberlite in relation to other pipes that comprise the property. C. Morphology of the Panda kimberlite pipe <xref ref-type="bibr" rid="pone.0045537-Nowicki1">[8]</xref> and occurrence of wood. D. Fossil wood encrusted in olivine-rich volcaniclastic kimberlite. E. Photograph of the specimen characterized in this study. The wood was split when removed from the ore, revealing a sliver of opaque amber (9.5 cm long by 0.5 cm wide) in the xylem. F. RLS in transmitted light showing uniseriate and biseriate bordered pits and cross-fields. G. TLS showing rays stacked 3–26 cells high. H. SEM (TS) of ring boundary with earlywood (left) and latewood (right). I. Close-up of tracheids in TS and calcite crystals within cells (arrows). J. Cross-section of ray with cross-field pits. K and L. Close-ups of cross-field pits. M. TLS close-up of rays. N. Radial longitudinal section showing four contiguous rows of ray parenchyma cells with smooth end walls and no separation between the individual rows of cells.</p></caption><graphic xlink:href="pone.0045537.g001"></graphic></fig><p>The Panda kimberlite is one of approximately 150 pipes in the Lac de Gras field with emplacement ages ranging from 45 to 75 Ma <xref ref-type="bibr" rid="pone.0045537-Nowicki1">[8]</xref>. The Panda pipe has a small diameter (∼200 m) and relatively simple geometry (<xref ref-type="fig" rid="pone-0045537-g001">Fig. 1</xref>), with no evidence of multiple phreatomagmatic events. Two additional pipes, Koala and Koala North, are emplaced immediately to the southwest of Panda; all three have been exploited by open-pit diamond mining. The age of the Panda intrusion has been dated precisely by Rb-Sr determinations on kimberlitic phlogopite (<italic>n</italic> = 7), yielding a robust isochron of 53.3±0.6 Ma (Early Eocene, Ypresian) <xref ref-type="bibr" rid="pone.0045537-Creaser1">[9]</xref>. Wood is common in the upper 300 m of the kimberlite body, and small rounded fragments (<10 cm) are often floated during rinsing of crushed ores. Larger wood fragments (>50 cm) have been retrieved directly from the ore before crushing; these are typically encrusted in reworked volcaniclastic kimberlite (<xref ref-type="fig" rid="pone-0045537-g001">Fig. 1D</xref>). We focus on one such specimen obtained from BHP Billiton and originating from the 315 m bench of the mine. The specimen is exceptional because of its size and the preservation of an amber nodule revealed within the xylem upon splitting (<xref ref-type="fig" rid="pone-0045537-g001">Fig. 1E</xref>). This offers the rare opportunity to conduct parallel geochemical investigations of the wood and associated amber, and to diagnose the wood anatomically. We envisage that the source tree collapsed into the diatreme at the time of kimberlite emplacement. The great depth of burial suggests that it entered a narrow marginal boundary layer between the blast zone and the wall rock before becoming entombed. We consider the wood to be representative of the Early Eocene forest growing at the site at the time of magmatism. The lack of permineralization suggests that burial was rapid, and that little post-eruptive thermal or tectonic alteration has occurred at the locality.</p></sec><sec id="s2"><title>Results and Discussion</title><sec id="s2a"><title>Wood Anatomy and Identity</title><p>Wood from the Panda kimberlite has pristine preservation (<xref ref-type="fig" rid="pone-0045537-g001">Fig. 1</xref>). Only the exterior of the specimen (<1 mm) is fusinized, implying that little free oxygen was present at the time of burial. Tracheids measure up to 62 µm in tangential diameter. In radial longitudinal section (RLS), earlywood tracheids exhibit uniseriate (58%) and biseriate (36%) bordered pits, with the remainder unpitted. Pits are circular (diameter: 15–20 µm) and are characterized by circular apertures (5–6 µm) arranged in contiguous chains of 1–8 cells. Multiseriate bordered pits have dominantly opposite arrangement (98%). Crassulae are present. Rays possess thin horizontal walls composed of cells up to 248 µm long, 10 µm high, and 12 µm wide. Cross-fields have 1–3 oppositely arranged taxodioid-cupressoid pits per field. Axial parenchyma consists of vertically stacked cells up to 160 µm in height, with both smooth (65%) and nodular (35%) end-walls. Axial tracheid walls are sparsely pitted in tangential longitudinal section (TLS). Rays are 3–26 cells high and dominantly uniseriate (97%). In transverse section (TS), growth rings are narrow (1.5–2.0 mm) with marked boundaries between latewood (35–49 µm) and earlywood (10–15 µm) cells. Near the ring boundary, rays are up to 2.5 mm long and spaced on average 70 µm apart (i.e. 12–14 rays per mm). Both horizontal and axial resin ducts are absent.</p><p>These features collectively identify the Panda wood as <italic>Taxodioxylon</italic> Hartig 1848 <xref ref-type="bibr" rid="pone.0045537-Krusel1">[10]</xref>–<xref ref-type="bibr" rid="pone.0045537-Meijer1">[12]</xref>. Moreover, fine anatomical details, including axial parenchyma with alternately nodular and smooth end-walls, single rows of taxodioid-cupressoid cross-field pits lacking separation between ray cells, and abrupt ring boundaries narrow the identification to <italic>Metasequoia</italic> Miki ex. Hu & Cheng 1948 <xref ref-type="bibr" rid="pone.0045537-Visscher1">[13]</xref>. <italic>Metasequoia</italic> was common in southern Alaska in the Late Paleocene and Early Eocene, producing a rich record of foliage and cones <xref ref-type="bibr" rid="pone.0045537-Sunderlin1">[14]</xref>. The genus is also abundant in younger (Middle Eocene, ca. 40 Ma) post-eruptive kimberlite maar sediments from the Slave Province, where it has been described as <italic>M. occidentalis</italic> (Newberry) Chaney <xref ref-type="bibr" rid="pone.0045537-Doria1">[7]</xref>. The latter taxon is likely conspecific with the only extant congener, <italic>M. glyptostroboides</italic> Hu & Cheng, at present native only to isolated montane tracts in south-central China <xref ref-type="bibr" rid="pone.0045537-Visscher1">[13]</xref>.</p></sec><sec id="s2b"><title>Cellulose Preservation</title><p>Cellulose preservation in fossil conifers varies tremendously given the labile nature of constituent polysaccharides, mandating the need for quality control prior to isotopic analysis <xref ref-type="bibr" rid="pone.0045537-Richter1">[15]</xref>. When viewed under scanning electron microscopy (SEM), extracts from Panda <italic>Metasequoia</italic> yield fibrous white material having the characteristic texture of wood cellulose (<xref ref-type="fig" rid="pone-0045537-g002">Fig. 2A–B</xref>). Fourier transform infrared (FTIR) spectra of the extracts support this contention: major absorption peaks including CH<sub>2</sub> deformation (900 cm<sup>−1</sup>) and CH<sub>3</sub> skeletal vibration (1375 cm<sup>−1</sup>) are common to both the Panda extracts and laboratory standard α-cellulose (<xref ref-type="fig" rid="pone-0045537-g002">Fig. 2C</xref>), yielding spectra that are fundamentally different from hemi- and holocellulose <xref ref-type="bibr" rid="pone.0045537-Rhoads1">[16]</xref>. Furthermore, the removal of hemicellulose with NaOH results in markedly more crystalline x-ray diffraction patterns (<xref ref-type="fig" rid="pone-0045537-g002">Fig. 2D</xref>), which lends support to the contention that these extracts are primarily α-cellulose <xref ref-type="bibr" rid="pone.0045537-Terinte1">[17]</xref>. To our knowledge, this is the oldest verified instance of α-cellulose preservation to date, testifying to the remarkable preservation potential of kimberlite-hosted wood.</p><fig id="pone-0045537-g002" orientation="portrait" position="float"><object-id pub-id-type="doi">10.1371/journal.pone.0045537.g002</object-id><label>Figure 2</label><caption><title>Cellulose extracted from Panda <italic>Metasequoia</italic>.</title><p>A. SEM of cellulose fibers at low magnification. B. SEM at higher magnification showing surface texture. C. Duplicate FTIR spectra (800–1500 cm<sup>−1</sup>) of the same material, shown in relation to Middle Eocene cellulose from Axel Heiberg Island <italic>Metasequoia</italic><xref ref-type="bibr" rid="pone.0045537-Richter1">[15]</xref> and laboratory standard (Sigma-Aldrich) α-cellulose. D. X-ray diffraction traces of Panda cellulose extracts before (grey) and after (black) treatment with NaOH. Peaks associated with α-cellulose crystallinity are indicated by vertical dashed lines, whereas the idealized spectrum of pure α-cellulose is shown above the Panda traces <xref ref-type="bibr" rid="pone.0045537-Terinte1">[17]</xref>.</p></caption><graphic xlink:href="pone.0045537.g002"></graphic></fig></sec><sec id="s2c"><title>Amber Spectroscopy and Thermal Alteration</title><p>FTIR spectra of amber fragments from the Panda wood indicate that they are dominantly composed of polylabdanoid diterpenes in the absence of succinic acid; the material is therefore classified tentatively as a Class 1b amber, consistent with other deposits attributed to cupressaceous conifers <xref ref-type="bibr" rid="pone.0045537-Anderson1">[18]</xref>. Indeed, FTIR spectra conform to modern and unaltered fossil <italic>Metasequoia</italic> resins in several regards (<xref ref-type="fig" rid="pone-0045537-g003">Fig. 3</xref>). The out-of-plane C = H deformation bands typical of cupressaceous conifers (887 and 975 cm<sup>−1</sup>) are well expressed in both materials, as are the positions of peaks associated with C–O stretching (1030 cm<sup>−1</sup>), CH<sub>2</sub> (2847 cm<sup>−1</sup>), and CH<sub>3</sub> (2870 cm<sup>−1</sup>) <xref ref-type="bibr" rid="pone.0045537-Tappert1">[19]</xref>. However, the Panda specimens have stronger broad-band O–H (3300–3400 cm<sup>−1</sup>), markedly reduced C = O in COOH (1693 cm<sup>−1</sup>), and greatly enhanced aromatic C = C (1520 cm<sup>−1</sup>) absorption bands relative to other congeneric resins. These features are well expressed by the spectroscopic difference between Panda amber and modern <italic>Metasequoia</italic> resins (<xref ref-type="fig" rid="pone-0045537-g003">Fig. 3E</xref>), and are interpreted to reflect a diagenetic sequence involving decarboxylation of cyclic hydrocarbons to more aromatic compounds, as observed elsewhere in the thermal maturation of conifer resins <xref ref-type="bibr" rid="pone.0045537-Otto1">[20]</xref>. Abiotic processes operating under anoxic conditions are responsible for these chemical transformations. Additional observations are consistent with some degree of thermal alteration in the Panda material, including the opacity of the amber owed to microscopic bubble inclusions (<xref ref-type="fig" rid="pone-0045537-g003">Fig. 3</xref>), the fusinization of wood outer surfaces, and the presence of calcite (CaCO<sub>3</sub>) crystals in wood cells (<xref ref-type="fig" rid="pone-0045537-g001">Fig. 1I</xref>), as confirmed by SEM-based energy dispersive spectroscopy. Calcite crystals are interpreted as <italic>in situ</italic> pseudomorphs following calcium oxalate (CaC<sub>2</sub>O<sub>4</sub>) initially produced by secondary metabolism in the living tree prior to burial <xref ref-type="bibr" rid="pone.0045537-Hudgins1">[21]</xref>.</p><fig id="pone-0045537-g003" orientation="portrait" position="float"><object-id pub-id-type="doi">10.1371/journal.pone.0045537.g003</object-id><label>Figure 3</label><caption><title>Complete FTIR spectra (650–4000 cm<sup>−1</sup>) of fossil and modern <italic>Metasequoia</italic> resins.</title><p>A–B. duplicate analyses of the amber from Panda wood. C. Middle Eocene amber from post-eruptive sediments in the Giraffe kimberlite pipe, which has not been thermally altered <xref ref-type="bibr" rid="pone.0045537-Doria1">[7]</xref>, <xref ref-type="bibr" rid="pone.0045537-Tappert1">[19]</xref>. Insets show typical fragments of Panda and Giraffe <italic>Metasequoia</italic> ambers (scale bars are 5 mm). D. Modern resin from <italic>M. glyptostroboides</italic> cultivar (Washington DC, USA) is visually identical to the Giraffe material. E. The spectroscopic differences between Panda and modern <italic>Metasequoia</italic> resins reveals features associated with thermal maturation (grey area is±1 SD of the difference).</p></caption><graphic xlink:href="pone.0045537.g003"></graphic></fig><p>Although it remains difficult to constrain eruptive temperatures during kimberlite emplacement due to the potential variability of volatile content and proximity to the local water table at the time of eruption, these are likely to have been in the 800–1200°C range initially, with the potential for considerable chilling (to 90–140°C) associated with adiabatic expansion during ascent <xref ref-type="bibr" rid="pone.0045537-Wilson1">[1]</xref>, <xref ref-type="bibr" rid="pone.0045537-Kavanagh1">[22]</xref>. Thermal maturation of organic macerals from a range of Slave Province kimberlite diatreme facies has been evaluated by vitrinite reflectance, revealing maximum diagenetic temperatures of 350–450°C <xref ref-type="bibr" rid="pone.0045537-Stasiuk1">[23]</xref>. Wood from the Panda pipe has no cellular damage associated with devolatilization, whereas resin FTIR spectra provide no evidence for dehydration, confirming that the material was not exposed to exceedingly high temperatures (i.e. >500°C) upon burial. Despite the relatively subtle features attributed to thermal alteration noted above, we find little evidence that either the quality of cellulose preservation or the isotopic signatures of the various analyzed fractions have been overprinted. We thus envisage that cooling of the igneous body following emplacement in the diatreme was extremely rapid, potentially near-instantaneous <xref ref-type="bibr" rid="pone.0045537-Wilson1">[1]</xref>, and surmise that any chemical changes to the entombed organic matter occurred in a closed system.</p></sec><sec id="s2d"><title>Stable Isotopes and Paleoclimatic Inferences</title><p>Stable isotopic results from Panda cellulose and amber (<xref ref-type="table" rid="pone-0045537-t001">Table 1</xref>) can be used to develop a range of inferences concerning the conditions under which tree growth occurred. Highly depleted mean δ<sup>2</sup>H values were obtained from nitrated wood cellulose samples (−160.5±3.8‰, <italic>n</italic> = 4). Using the accepted relationship between tree cellulose and surface water δ2H <xref ref-type="bibr" rid="pone.0045537-Epstein1">[24]</xref>, this translates to an average δ2H of −138‰ for environmental waters accessed by the tree (<xref ref-type="table" rid="pone-0045537-t001">Table 1</xref>). In the modern North American isoscape, this corresponds to a boreal environment <xref ref-type="bibr" rid="pone.0045537-West1">[25]</xref>. In the Early Eocene, isotopically-depleted precipitation influenced drainage to the Arctic Ocean immediately following the Paleocene-Eocene Thermal Maximum (PETM; 55.5 Ma), inscribing low δ<sup>2</sup>H values on a range of terrestrial biomarkers <xref ref-type="bibr" rid="pone.0045537-Pagani1">[26]</xref>. Indeed, these authors propose a range of δ<sup>2</sup>H values for precipitation in the post-PETM Arctic (−105 to −145‰) that encompasses the inferred environmental water δ<sup>2</sup>H from Panda tree cellulose (−138‰).</p><table-wrap id="pone-0045537-t001" orientation="portrait" position="float"><object-id pub-id-type="doi">10.1371/journal.pone.0045537.t001</object-id><label>Table 1</label><caption><title>Stable isotopic ratios of amber and cellulose extracted from <italic>Metasequoia</italic> wood entombed in the Panda kimberlite.</title></caption><alternatives><graphic id="pone-0045537-t001-1" xlink:href="pone.0045537.t001"></graphic><table frame="hsides" rules="groups"><colgroup span="1"><col align="left" span="1"></col><col align="center" span="1"></col><col align="center" span="1"></col><col align="center" span="1"></col><col align="center" span="1"></col><col align="center" span="1"></col></colgroup><thead><tr><td align="left" rowspan="1" colspan="1">Measurement</td><td align="left" rowspan="1" colspan="1">Minimum</td><td align="left" rowspan="1" colspan="1">Maximum</td><td align="left" rowspan="1" colspan="1">Mean</td><td align="left" rowspan="1" colspan="1">±1 s.d.</td><td align="left" rowspan="1" colspan="1"><italic>n</italic></td></tr></thead><tbody><tr><td align="left" rowspan="1" colspan="1">Amber δ<xref ref-type="table-fn" rid="nt102">2</xref>H (‰ VSMOW)</td><td align="left" rowspan="1" colspan="1">−371.09</td><td align="left" rowspan="1" colspan="1">−363.90</td><td align="left" rowspan="1" colspan="1">−368.95</td><td align="left" rowspan="1" colspan="1">2.59</td><td align="left" rowspan="1" colspan="1">6</td></tr><tr><td align="left" rowspan="1" colspan="1">Cellulose δ<xref ref-type="table-fn" rid="nt102">2</xref>H (‰ VSMOW)</td><td align="left" rowspan="1" colspan="1">−165.06</td><td align="left" rowspan="1" colspan="1">−156.34</td><td align="left" rowspan="1" colspan="1">−160.54</td><td align="left" rowspan="1" colspan="1">3.78</td><td align="left" rowspan="1" colspan="1">4</td></tr><tr><td align="left" rowspan="1" colspan="1">Inferred δ<xref ref-type="table-fn" rid="nt102">2</xref>H<sub>environmental water</sub> (‰ VSMOW)<xref ref-type="table-fn" rid="nt101">1</xref></td><td align="left" rowspan="1" colspan="1">−143.06</td><td align="left" rowspan="1" colspan="1">−134.34</td><td align="left" rowspan="1" colspan="1">−138.54</td><td align="left" rowspan="1" colspan="1">−</td><td align="left" rowspan="1" colspan="1">−</td></tr><tr><td align="left" rowspan="1" colspan="1">Amber δ<sup>13</sup>C (‰ VPDB)</td><td align="left" rowspan="1" colspan="1">−25.17</td><td align="left" rowspan="1" colspan="1">−24.56</td><td align="left" rowspan="1" colspan="1">−24.83</td><td align="left" rowspan="1" colspan="1">0.22</td><td align="left" rowspan="1" colspan="1">6</td></tr><tr><td align="left" rowspan="1" colspan="1">Cellulose δ<sup>13</sup>C (‰ VPDB)</td><td align="left" rowspan="1" colspan="1">−19.84</td><td align="left" rowspan="1" colspan="1">−19.65</td><td align="left" rowspan="1" colspan="1">−19.74</td><td align="left" rowspan="1" colspan="1">0.13</td><td align="left" rowspan="1" colspan="1">2</td></tr><tr><td align="left" rowspan="1" colspan="1">Cellulose δ<sup>18</sup>O (‰ VSMOW)</td><td align="left" rowspan="1" colspan="1">18.52</td><td align="left" rowspan="1" colspan="1">18.75</td><td align="left" rowspan="1" colspan="1">18.61</td><td align="left" rowspan="1" colspan="1">0.12</td><td align="left" rowspan="1" colspan="1">4</td></tr><tr><td align="left" rowspan="1" colspan="1">Inferred δ<sup>18</sup>O<sub>environmental water</sub> (‰ VSMOW)<xref ref-type="table-fn" rid="nt102">2</xref></td><td align="left" rowspan="1" colspan="1">−16.48</td><td align="left" rowspan="1" colspan="1">−16.25</td><td align="left" rowspan="1" colspan="1">−16.39</td><td align="left" rowspan="1" colspan="1">−</td><td align="left" rowspan="1" colspan="1">−</td></tr></tbody></table></alternatives><table-wrap-foot><fn id="nt101"><label>1</label><p>using ε<sub>cellulose-environmental water</sub> = −22‰ <xref ref-type="bibr" rid="pone.0045537-Epstein1">[24]</xref>.</p></fn><fn id="nt102"><label>2</label><p>using ε<sub>cellulose-environmental water</sub> = 35‰ for <italic>Metasequoia</italic><xref ref-type="bibr" rid="pone.0045537-Jahren1">[31]</xref>.</p></fn></table-wrap-foot></table-wrap><p>Amber from the Panda locality also produced highly depleted δ<sup>2</sup>H values (−369.0±2.6‰, <italic>n</italic> = 6), although these are not exceptional by comparison to both Early Eocene cupressaceous ambers from Ellesmere Island (−354.2±5.3‰, <italic>n</italic> = 4; authors’ unpublished data) as well as mixed specimens from the Middle Eocene fossil forest of Axel Heiberg Island (−357.9±27.3‰, <italic>n</italic> = 6, <xref ref-type="bibr" rid="pone.0045537-Byrne1">[27]</xref>). Moreover, Panda amber δ<sup>13</sup>C values (−25.17±0.22‰) are well within the range reported for ambers of various age and provenance <xref ref-type="bibr" rid="pone.0045537-McKellar1">[28]</xref>. These similarities are inconsistent with the notion that the Panda amber isotopic signature has been altered during the burial process. Thus, the cellulose-based estimate of δ<sup>2</sup>H<sub>environmental water</sub> derived above implies that Panda amber is depleted relative to water by 229‰ (range: 228–230‰). This fractionation is slightly less than the range (238–303‰) obtained experimentally for diterpenoids synthesized by the non-mevalonate (or MEP/DOXP: 2-<italic>C</italic>-methyl-D-erythritol 4-phosphate/1-deoxy-D-xylulose 5-phosphate) pathway in the living cupressaceous conifer <italic>Cryptomeria japonica</italic><xref ref-type="bibr" rid="pone.0045537-Chikaraishi1">[29]</xref>. As this biochemical pathway is an essential precursor to the resin diterpenoids that polymerize to form amber, we consider the Panda δ<sup>2</sup>H values to capture the primary isotopic signature of resin metabolism, with no discernible evidence of diagenetic overprinting. Recent experimental observations, where <italic>Metasequoia</italic> resins were heated at 90°C in deuterated water and sampled monthly over a period of one year, support the notion of limited exchangeability of H (i.e. <5%) following initial resin biosynthesis <xref ref-type="bibr" rid="pone.0045537-Gonzalez1">[30]</xref>.</p><p>The δ<sup>18</sup>O of Panda cellulose ranges from 18.5–18.8‰, implying a mean δ<sup>18</sup>O<sub>environmental water</sub> of −16.4‰ using a constant enrichment of 35‰ between cellulose and water observed in modern <italic>Metasequoia</italic><xref ref-type="bibr" rid="pone.0045537-Jahren1">[31]</xref>. Using schemes based on cellulose δ<sup>13</sup>C <xref ref-type="bibr" rid="pone.0045537-Lipp1">[32]</xref> and paired δ<sup>18</sup>O and δ<sup>2</sup>H <xref ref-type="bibr" rid="pone.0045537-Jahren2">[33]</xref>, we computed a likely range of ambient relative humidity (RH) values, resulting in mean, minimum, and maximum RH of 77%, 64% and 83%, respectively. These estimates are consistent with the RH of 75% derived independently from an Early Eocene (52–53 Ma) vertebrate assemblage on Ellesmere Island <xref ref-type="bibr" rid="pone.0045537-Eberle1">[34]</xref>. We then applied these RH estimates to estimate δ<sup>18</sup>O<sub>precipitation</sub> using two alternate methods <xref ref-type="bibr" rid="pone.0045537-Roden1">[35]</xref>, <xref ref-type="bibr" rid="pone.0045537-Anderson2">[36]</xref> and derived corresponding mean annual temperatures using Eocene latitudinal gradients <xref ref-type="bibr" rid="pone.0045537-Fricke1">[37]</xref>. These results produce MAT estimates of 7–12°C, with a grand mean of 9°C (<xref ref-type="table" rid="pone-0045537-t002">Table 2</xref>). Present MAT at Yellowknife is −4.6°C <xref ref-type="bibr" rid="pone.0045537-Environment1">[38]</xref>. Thus, in the Early Eocene, the Panda locality was in the order of 12–17°C warmer than present.</p><table-wrap id="pone-0045537-t002" orientation="portrait" position="float"><object-id pub-id-type="doi">10.1371/journal.pone.0045537.t002</object-id><label>Table 2</label><caption><title>Two estimates of Early Eocene δ<sup>18</sup>O<sub>precipitation</sub><xref ref-type="bibr" rid="pone.0045537-Roden1">[35]</xref>, <xref ref-type="bibr" rid="pone.0045537-Anderson2">[36]</xref> and corresponding mean annual temperature (MAT) <xref ref-type="bibr" rid="pone.0045537-Fricke1">[37]</xref> derived from Panda cellulose for minimum, mean, and maximum inferred values of relative humidity (RH).</title></caption><alternatives><graphic id="pone-0045537-t002-2" xlink:href="pone.0045537.t002"></graphic><table frame="hsides" rules="groups"><colgroup span="1"><col align="left" span="1"></col><col align="center" span="1"></col><col align="center" span="1"></col><col align="center" span="1"></col></colgroup><thead><tr><td colspan="2" align="left" rowspan="1">Relative humidity</td><td align="left" rowspan="1" colspan="1">ref. <xref ref-type="bibr" rid="pone.0045537-Pagani1">[26]</xref></td><td align="left" rowspan="1" colspan="1">ref. <xref ref-type="bibr" rid="pone.0045537-Byrne1">[27]</xref></td></tr></thead><tbody><tr><td colspan="2" align="left" rowspan="1">RH = 64%</td><td align="left" rowspan="1" colspan="1"></td><td align="left" rowspan="1" colspan="1"></td></tr><tr><td align="left" rowspan="1" colspan="1"></td><td align="left" rowspan="1" colspan="1">δ<sup>18</sup>O<sub>precipitation</sub> (‰)</td><td align="left" rowspan="1" colspan="1">−13.5</td><td align="left" rowspan="1" colspan="1">−12.9</td></tr><tr><td align="left" rowspan="1" colspan="1"></td><td align="left" rowspan="1" colspan="1">MAT (°C)</td><td align="left" rowspan="1" colspan="1">10.5</td><td align="left" rowspan="1" colspan="1">7.0</td></tr><tr><td colspan="2" align="left" rowspan="1">RH = 77%</td><td align="left" rowspan="1" colspan="1"></td><td align="left" rowspan="1" colspan="1"></td></tr><tr><td align="left" rowspan="1" colspan="1"></td><td align="left" rowspan="1" colspan="1">δ<sup>18</sup>O<sub>precipitation</sub> (‰)</td><td align="left" rowspan="1" colspan="1">−15.9</td><td align="left" rowspan="1" colspan="1">−14.0</td></tr><tr><td align="left" rowspan="1" colspan="1"></td><td align="left" rowspan="1" colspan="1">MAT (°C)</td><td align="left" rowspan="1" colspan="1">7.7</td><td align="left" rowspan="1" colspan="1">10.3</td></tr><tr><td colspan="2" align="left" rowspan="1">RH = 83%</td><td align="left" rowspan="1" colspan="1"></td><td align="left" rowspan="1" colspan="1"></td></tr><tr><td align="left" rowspan="1" colspan="1"></td><td align="left" rowspan="1" colspan="1">δ<sup>18</sup>O<sub>precipitation</sub> (‰)</td><td align="left" rowspan="1" colspan="1">−17.0</td><td align="left" rowspan="1" colspan="1">−17.4</td></tr><tr><td align="left" rowspan="1" colspan="1"></td><td align="left" rowspan="1" colspan="1">MAT (°C)</td><td align="left" rowspan="1" colspan="1">6.4</td><td align="left" rowspan="1" colspan="1">12.0</td></tr></tbody></table></alternatives></table-wrap><p>These results can be compared to the MAT of 8°C and warmest month temperature of 19–20°C inferred for the Early Eocene on Ellesmere Island <xref ref-type="bibr" rid="pone.0045537-Eberle1">[34]</xref>. Leaf margin analyses from Paleocene-Eocene sediments in southern Alaska produce MAT estimates of 11–14°C and warmest month temperatures of 22°C <xref ref-type="bibr" rid="pone.0045537-Sunderlin1">[14]</xref>. Together, these estimates converge on the warm-temperate character of Early Eocene high-latitude climates, with greatly reduced seasonality relative to present. At the same time, conditions at the Panda locality must have been considerably more humid than present. This is because <italic>Metasequoia</italic> requires >1000 mm of annual precipitation in order to thrive <xref ref-type="bibr" rid="pone.0045537-LePage1">[39]</xref>, roughly four times more precipitation than received at Yellowknife today (280 mm, <xref ref-type="bibr" rid="pone.0045537-Environment1">[38]</xref>). The humid conditions envisaged for the Arctic Ocean basin during the Early Eocene <xref ref-type="bibr" rid="pone.0045537-Sluijs1">[40]</xref> clearly extended to subarctic latitudes of the North American interior.</p><p>The MAT reconstructions presented in <xref ref-type="table" rid="pone-0045537-t002">Table 2</xref> are corroborated by an additional analysis: the comparison of Panda cellulose isotopic composition with that of precipitation at Yellowknife, the nearest station (314 km to the southwest) for which a multi-year characterization exists for both δ<sup>2</sup>H and δ<sup>18</sup>O <xref ref-type="bibr" rid="pone.0045537-Birks1">[41]</xref>. The δ<sup>2</sup>H<sub>environmental water</sub> and δ<sup>18</sup>O<sub>environmental water</sub> values obtained from Panda wood cellulose using constant enrichment factors between water and cellulose were used (<xref ref-type="table" rid="pone-0045537-t001">Table 1</xref>), in order to minimize the effects of assumptions regarding RH. It can be shown that the δ<sup>2</sup>H and δ<sup>18</sup>O of source waters inferred from Panda wood cellulose plot closely to the local meteoric water line (<xref ref-type="fig" rid="pone-0045537-g004">Fig. 4A</xref>), strongly supporting the contention that mechanisms of Early Eocene atmospheric water transport bore remarkable similarities to the modern world <xref ref-type="bibr" rid="pone.0045537-Richter1">[15]</xref>, despite pronounced differences in precipitation quantity, ambient temperature, and seasonality. Moreoever, the Panda data plot intermediately between the mean modern Yellowknife values for May and September, and those for June, July and August, the warmest months (<xref ref-type="fig" rid="pone-0045537-g004">Fig. 4B</xref>). The corresponding monthly mean temperatures are entirely compatible with MAT estimates based on empirical relationships applied to the Panda wood isotopic composition (<xref ref-type="table" rid="pone-0045537-t002">Table 2</xref>). When the modern temperature dependencies of precipitation δ<sup>2</sup>H and δ<sup>18</sup>O from Yellowknife are plotted independently, inferred environmental water isotopic values from Panda cellulose imply temperatures of 11°C and 17°C, respectively (<xref ref-type="fig" rid="pone-0045537-g004">Fig. 4C–D</xref>). These values are several degrees warmer than the MAT estimates of <xref ref-type="table" rid="pone-0045537-t002">Table 2</xref>, and are thus likely to reflect the warm season of active biomass accrual only. From these various analyses, we surmise that the Panda cellulose isotopic measurements provide robust and highly coherent paleoclimatic information for the Early Eocene in northwestern Canada, thus filling a large geographic void with respect to the closest contemporaneous fossil localities <xref ref-type="bibr" rid="pone.0045537-Sunderlin1">[14]</xref>, <xref ref-type="bibr" rid="pone.0045537-Eberle1">[34]</xref>.</p><fig id="pone-0045537-g004" orientation="portrait" position="float"><object-id pub-id-type="doi">10.1371/journal.pone.0045537.g004</object-id><label>Figure 4</label><caption><title>Mean monthly δ<sup>18</sup>O and δ<sup>2</sup>H of precipitation at Yellowknife (Station 7193401, 62.28°N, 114.27°W, 205 m, <xref ref-type="bibr" rid="pone.0045537-Birks1">[41]</xref>), shown in relation to inferred values of environmental waters accessed by Panda <italic>Metasequoia</italic>.</title><p>A. Monthly values for the five-year measurement period (1989–1993) depict a local meteoric water line (LMWL) that deviates only slightly from the Global Meteoric Water Line (GMWL). The Panda cellulose isotopic values, once converted to the composition of environmental water (<xref ref-type="table" rid="pone-0045537-t001">Table 1</xref>), plot on the LMWL. B. Magnification of the shaded grey in A, showing mean monthly isotopic values for months between May and September, corresponding mean monthly temperatures for the observation period (<italic>n</italic> = 5), and the mean value derived from Panda wood cellulose (<italic>n</italic> = 4). C. Temperature dependency of modern precipitation δ<sup>2</sup>H at Yellowknife and the inferred range of values obtained from Panda cellulose, with extrapolated temperature estimates (dashed vertical line). D. As for C, but for precipitation δ<sup>18</sup>O.</p></caption><graphic xlink:href="pone.0045537.g004"></graphic></fig></sec><sec id="s2e"><title>Conclusions</title><p>Due to the coupled effects of multiple denudational phases and pervasive Neogene glacial erosion, the ∼210,000 km<sup>2</sup> expanse of the Slave Craton lacks traditional Phanerozoic fossil exposures <xref ref-type="bibr" rid="pone.0045537-Ault1">[42]</xref>. Kimberlites revealed by diamond exploration and mining thus provide the sole repository of paleobiological information for this large expanse of Northwestern Canada. Although deep burial in volcaniclastic kimberlite is an unconventional source for Lagerstätte-quality plant megafossils, we have demonstrated that such a record indeed exists in the Panda pipe, and likely in other Slave Province kimberlitic intrusions where wood has been documented <xref ref-type="bibr" rid="pone.0045537-Nassichuk1">[4]</xref>, <xref ref-type="bibr" rid="pone.0045537-Nowicki1">[8]</xref>, <xref ref-type="bibr" rid="pone.0045537-Stasiuk1">[23]</xref>. The state of preservation of this wood is unequalled for material of this age, as exemplified by the exquisite quality of anatomical detail and the presence of α-cellulose. This exceptional preservation has enabled a range of isotopic measurements that provide a provisional reconstruction of the mean climate state under which tree growth occurred. In the Early Eocene, immediately following peak Cenozoic warmth driven by enhanced greenhouse gas forcing <xref ref-type="bibr" rid="pone.0045537-Zachos1">[43]</xref>, the subarctic latitudes of the Slave Province harbored <italic>Metasequoia</italic> in forests developed under conditions 12–17°C warmer and four times wetter than at present.</p></sec></sec><sec sec-type="materials|methods" id="s3"><title>Materials and Methods</title><p>The wood specimen considered here was archived in the core lab of BHP Billiton Diamonds Inc., then located in Kelowna, British Columbia, Canada. BHP granted permission to sample the Panda wood material, and donated the specimen to the University of Alberta for further analyses. No additional permissions were required to undertake the study.</p><p>We sectioned transverse (TS), radial longitudinal (RLS) and tangential longitudinal (TLS) planes of the wood, embedded them under vacuum in Epothin, and ground thin sections for examination under transmitted light microscopy. The wood was easily dissected by scalpel. The same planes of unimpregnated wood were also examined using field-emission SEM on a JEOL-6301F system operating at 25 kV, following sputter-coating with Au. For isotopic analyses, cellulose was extracted from wood samples using a modified Jayme-Wise method <xref ref-type="bibr" rid="pone.0045537-Gaudinski1">[44]</xref>, where ground samples were refluxed by soxhlet in toluene and ethanol to remove resins, delignified in an acidified NaClO<sub>2</sub> solution, washed in NaOH to remove hemicellulose, and leached of Fe and Mn oxyhydroxides using hydroxylamine hydrochloride (H<sub>3</sub>NO•HCl). Purified cellulose extracts were examined by SEM and characterized by FTIR spectroscopy with a Thermo-Nicolet Nexus 470 bench spectrometer fitted with a dual-aperture Continuum infrared microscope. These extracts were also analyzed by x-ray diffraction, using a Rigaku Geigerflex powder diffractometer equipped with a cobalt tube, graphite monochromator, and scintillation detector. The occluded amber was also analyzed by FTIR and compared to a broad array of modern and fossil resin spectra <xref ref-type="bibr" rid="pone.0045537-Tappert1">[19]</xref>.</p><p>A range of stable isotopic measurements were made on these materials: δ<sup>2</sup>H (<italic>n</italic> = 4), δ<sup>13</sup>C (<italic>n</italic> = 2) and δ<sup>18</sup>O (<italic>n</italic> = 4) were measured from wood cellulose extracts, whereas δ<sup>2</sup>H (<italic>n</italic> = 6) and δ<sup>13</sup>C (<italic>n</italic> = 6) were measured from untreated amber fragments. Prior to the measurement of δ<sup>2</sup>H, cellulose was nitrated with phosphorus pentoxide to remove exchangeable H <xref ref-type="bibr" rid="pone.0045537-Sternberg1">[45]</xref>. Cellulose δ<sup>2</sup>H and δ<sup>18</sup>O were measured at the University of Arizona using a Thermo Finnigan Delta Plus XL isotope-ratio mass spectrometer in continuous flow mode coupled to a Thermo Finnigan TC/EA via a Conflo III interface. Carbon and hydrogen isotope ratios of amber, and carbon isotopes of cellulose, were measured at the University of Alberta using a Finnigan MAT-252 isotope-ratio mass spectrometer in dual-inlet mode. Isotopic results are expressed in δ notation relative to Vienna Standard Mean Ocean Water (VSMOW) for δD and δ<sup>18</sup>O, and Pee Dee Belemnite (VPDB) for δ<sup>13</sup>C. Precision was±3‰ for δD and±0.1‰ for δ<sup>13</sup>C and δ<sup>18</sup>O.</p></sec></body><back><ack><p>We thank BHP Billiton Diamonds Inc. for access to samples then housed in Kelowna, and generously offered for study by J. Carlson, B. Crawford and D. Dyck. FTIR and SEM investigations were facilitated by T. Stachel and G. Braybrook, respectively, and constructive criticism was provided by anonymous journal reviewers and the Academic Editor, Lee Newsom.</p></ack><ref-list><title>References</title><ref id="pone.0045537-Wilson1"><label>1</label><mixed-citation publication-type="journal"><name><surname>Wilson</surname><given-names>L</given-names></name>, <name><surname>Head</surname><given-names>JW</given-names><suffix>III</suffix></name> (<year>2007</year>) <article-title>An integrated model of kimberlite ascent and eruption</article-title>. <source>Nature</source><volume>447</volume>: <fpage>53</fpage>–<lpage>57</lpage><pub-id pub-id-type="pmid">17476260</pub-id></mixed-citation></ref><ref id="pone.0045537-Edwards1"><label>2</label><mixed-citation publication-type="journal"><name><surname>Edwards</surname><given-names>B</given-names></name>, <name><surname>Howkins</surname><given-names>B</given-names></name> (<year>1966</year>) <article-title>Kimberlites in Tanganyika with special reference to the Mwadui occurrence</article-title>. <source>Econ Geol</source><volume>61</volume>: <fpage>537</fpage>–<lpage>554</lpage></mixed-citation></ref><ref id="pone.0045537-Smith1"><label>3</label><mixed-citation publication-type="journal"><name><surname>Smith</surname><given-names>RMH</given-names></name> (<year>1986</year>) <article-title>Sedimentation and palaeoenvironments of Late Cretaceous crater-lake deposits in Bushmanland, South Africa</article-title>. <source>Sedimentology</source><volume>33</volume>: <fpage>369</fpage>–<lpage>386</lpage></mixed-citation></ref><ref id="pone.0045537-Nassichuk1"><label>4</label><mixed-citation publication-type="other">Nassichuk WW, McIntyre DJ (1995) Cretaceous and Tertiary fossils discovered in kimberlites at Lac de Gras in the Slave Province, Northwest Territories: Geological Survey of Canada Current Research 1995-B, p.109–114.</mixed-citation></ref><ref id="pone.0045537-Cookenboo1"><label>5</label><mixed-citation publication-type="journal"><name><surname>Cookenboo</surname><given-names>HO</given-names></name>, <name><surname>Orchard</surname><given-names>MJ</given-names></name>, <name><surname>Daoud</surname><given-names>DK</given-names></name> (<year>1998</year>) <article-title>Remnants of Paleozoic cover on the Archean Canadian Shield: limestone xenoliths from kimberlite in the central Slave craton</article-title>. <source>Geology</source><volume>26</volume>: <fpage>391</fpage>–<lpage>394</lpage></mixed-citation></ref><ref id="pone.0045537-Wolfe1"><label>6</label><mixed-citation publication-type="journal"><name><surname>Wolfe</surname><given-names>AP</given-names></name>, <name><surname>Siver</surname><given-names>PA</given-names></name> (<year>2009</year>) <article-title>Three genera of extant thalassiosiroid diatoms from Middle Eocene lake sediments in northern Canada</article-title>. <source>Am J Bot</source><volume>96</volume>: <fpage>487</fpage>–<lpage>497</lpage><pub-id pub-id-type="pmid">21628204</pub-id></mixed-citation></ref><ref id="pone.0045537-Doria1"><label>7</label><mixed-citation publication-type="journal"><name><surname>Doria</surname><given-names>G</given-names></name>, <name><surname>Royer</surname><given-names>DL</given-names></name>, <name><surname>Wolfe</surname><given-names>AP</given-names></name>, <name><surname>Fox</surname><given-names>A</given-names></name>, <name><surname>Westgate</surname><given-names>JA</given-names></name>, <name><surname>Beerling</surname><given-names>DJ</given-names></name> (<year>2011</year>) <article-title>Declining atmospheric CO2 during the late Middle Eocene climate transition</article-title>. <source>Am J Sci</source><volume>311</volume>: <fpage>63</fpage>–<lpage>75</lpage></mixed-citation></ref><ref id="pone.0045537-Nowicki1"><label>8</label><mixed-citation publication-type="journal"><name><surname>Nowicki</surname><given-names>T</given-names></name>, <name><surname>Crawford</surname><given-names>B</given-names></name>, <name><surname>Dyck</surname><given-names>D</given-names></name>, <name><surname>Carlson</surname><given-names>J</given-names></name>, <name><surname>McElroy</surname><given-names>R</given-names></name>, <etal>et al</etal> (<year>2004</year>) <article-title>The geology of kimberlite pipes of the Ekati property, Northwest Territories, Canada</article-title>. <source>Lithos</source><volume>76</volume>: <fpage>1</fpage>–<lpage>27</lpage></mixed-citation></ref><ref id="pone.0045537-Creaser1"><label>9</label><mixed-citation publication-type="journal"><name><surname>Creaser</surname><given-names>RA</given-names></name>, <name><surname>Grütter</surname><given-names>HS</given-names></name>, <name><surname>Carlson</surname><given-names>J</given-names></name>, <name><surname>Crawford</surname><given-names>B</given-names></name> (<year>2004</year>) <article-title>Macrocrystal phlogopite Rb-Sr dates for the Ekati property kimberlites: evidence for multiple intrusive episodes during Paleocene and Eocene time</article-title>. <source>Lithos</source><volume>76</volume>: <fpage>399</fpage>–<lpage>414</lpage></mixed-citation></ref><ref id="pone.0045537-Krusel1"><label>10</label><mixed-citation publication-type="journal"><name><surname>Kräusel</surname><given-names>R</given-names></name> (<year>1949</year>) <article-title>Die fossilen koniferen-hölzer (unter Ausschluss von <italic>Araucarioxylon</italic> Kraus). II. Kritische untersuchungen zur diagnostik lebender und fossiler koniferen-hölzer. Paläontol. Abh. Abt</article-title>. <source>B</source><volume>89</volume>: <fpage>83</fpage>–<lpage>203</lpage></mixed-citation></ref><ref id="pone.0045537-Greguss1"><label>11</label><mixed-citation publication-type="other">Greguss P (1955) Identification of living gymnosperms on the basis of xylotomy. Budapest: Akadémiai Kiadó. 263 p.</mixed-citation></ref><ref id="pone.0045537-Meijer1"><label>12</label><mixed-citation publication-type="journal"><name><surname>Meijer</surname><given-names>JJF</given-names></name> (<year>2000</year>) <article-title>Fossil woods from the Late Cretaceous Aachen Formation</article-title>. <source>Rev Palaeobot Palynol</source><volume>112</volume>: <fpage>297</fpage>–<lpage>336</lpage><pub-id pub-id-type="pmid">11134711</pub-id></mixed-citation></ref><ref id="pone.0045537-Visscher1"><label>13</label><mixed-citation publication-type="journal"><name><surname>Visscher</surname><given-names>GE</given-names></name>, <name><surname>Jagels</surname><given-names>R</given-names></name> (<year>2003</year>) <article-title>Separation of <italic>Metasequoia</italic> and <italic>Glyptostrobus</italic> (Cupressaceae) based on wood anatomy</article-title>. <source>IAWA Journal</source><volume>24</volume>: <fpage>439</fpage>–<lpage>450</lpage></mixed-citation></ref><ref id="pone.0045537-Sunderlin1"><label>14</label><mixed-citation publication-type="journal"><name><surname>Sunderlin</surname><given-names>D</given-names></name>, <name><surname>Loope</surname><given-names>G</given-names></name>, <name><surname>Parker</surname><given-names>NE</given-names></name>, <name><surname>Williams</surname><given-names>CJ</given-names></name> (<year>2011</year>) <article-title>Paleoclimatic and paleoecological implications of a Paleocene-Eocene fossil leaf assemblage, Chickaloon Formation, Alaska</article-title>. <source>Palaios</source><volume>26</volume>: <fpage>335</fpage>–<lpage>345</lpage></mixed-citation></ref><ref id="pone.0045537-Richter1"><label>15</label><mixed-citation publication-type="journal"><name><surname>Richter</surname><given-names>SL</given-names></name>, <name><surname>Johnson</surname><given-names>AH</given-names></name>, <name><surname>Dranoff</surname><given-names>MM</given-names></name>, <name><surname>LePage</surname><given-names>BA</given-names></name>, <name><surname>Williams</surname><given-names>CJ</given-names></name> (<year>2008</year>) <article-title>Oxygen isotope ratios in fossil wood cellulose: isotopic composition of Eocene- to Holocene-aged cellulose</article-title>. <source>Geochim Cosmochim Acta</source><volume>72</volume>: <fpage>2744</fpage>–<lpage>2753</lpage></mixed-citation></ref><ref id="pone.0045537-Rhoads1"><label>16</label><mixed-citation publication-type="journal"><name><surname>Rhoads</surname><given-names>CA</given-names></name>, <name><surname>Painter</surname><given-names>PC</given-names></name>, <name><surname>Given</surname><given-names>PH</given-names></name> (<year>1987</year>) <article-title>FTIR studies of the contributions of plant polymers to coal formation</article-title>. <source>Int J Coal Geol</source><volume>8</volume>: <fpage>69</fpage>–<lpage>83</lpage></mixed-citation></ref><ref id="pone.0045537-Terinte1"><label>17</label><mixed-citation publication-type="journal"><name><surname>Terinte</surname><given-names>N</given-names></name>, <name><surname>Ibbett</surname><given-names>R</given-names></name>, <name><surname>Schuster</surname><given-names>KC</given-names></name> (<year>2011</year>) <article-title>Overview on native cellulose and microcrystalline cellular I structure studied by x-ray diffraction (WAXD): comparison between measurement techniques</article-title>. <source>Lenzinger Ber</source><volume>89</volume>: <fpage>118</fpage>–<lpage>131</lpage></mixed-citation></ref><ref id="pone.0045537-Anderson1"><label>18</label><mixed-citation publication-type="journal"><name><surname>Anderson</surname><given-names>KB</given-names></name> (<year>2006</year>) <article-title>The nature and fate of natural resins in the geosphere. XII. Investigation of C-ring aromatic diterpenoids in Raritan amber by pyrolysis-GC-matrix isolation FTIR-MS</article-title>. <source>Geochem T</source><volume>7</volume>: <fpage>2</fpage> doi:10.1186/1467-4866-7-2.</mixed-citation></ref><ref id="pone.0045537-Tappert1"><label>19</label><mixed-citation publication-type="journal"><name><surname>Tappert</surname><given-names>R</given-names></name>, <name><surname>Wolfe</surname><given-names>AP</given-names></name>, <name><surname>McKellar</surname><given-names>RC</given-names></name>, <name><surname>Tappert</surname><given-names>M</given-names></name>, <name><surname>Muehlenbachs</surname><given-names>K</given-names></name> (<year>2011</year>) <article-title>Characterizing modern and fossil conifer exudates using micro-FTIR spectroscopy</article-title>. <source>Int J Plant Sci</source><volume>172</volume>: <fpage>120</fpage>–<lpage>138</lpage></mixed-citation></ref><ref id="pone.0045537-Otto1"><label>20</label><mixed-citation publication-type="journal"><name><surname>Otto</surname><given-names>A</given-names></name>, <name><surname>Simoneit</surname><given-names>BRT</given-names></name>, <name><surname>Wilde</surname><given-names>V</given-names></name> (<year>2007</year>) <article-title>Terpenoids as chemosystematic markers in selected fossil and extant species of pine (<italic>Pinus</italic>, Pinaceae)</article-title>. <source>Bot J Linn Soc</source><volume>154</volume>: <fpage>129</fpage>–<lpage>140</lpage></mixed-citation></ref><ref id="pone.0045537-Hudgins1"><label>21</label><mixed-citation publication-type="journal"><name><surname>Hudgins</surname><given-names>JW</given-names></name>, <name><surname>Krekling</surname><given-names>T</given-names></name>, <name><surname>Franceschi</surname><given-names>VR</given-names></name> (<year>2003</year>) <article-title>Distribution of calcium oxalate crystals in the secondary phloem of conifers: a constitutive defense mechanism?</article-title><source>New Phytol</source><volume>159</volume>: <fpage>677</fpage>–<lpage>690</lpage></mixed-citation></ref><ref id="pone.0045537-Kavanagh1"><label>22</label><mixed-citation publication-type="journal"><name><surname>Kavanagh</surname><given-names>JL</given-names></name>, <name><surname>Sparks</surname><given-names>RS</given-names></name> (<year>2009</year>) <article-title>Temperature changes in ascending kimberlite magma</article-title>. <source>Earth Planet Sci Lett</source><volume>286</volume>: <fpage>404</fpage>–<lpage>413</lpage></mixed-citation></ref><ref id="pone.0045537-Stasiuk1"><label>23</label><mixed-citation publication-type="journal"><name><surname>Stasiuk</surname><given-names>LD</given-names></name>, <name><surname>Lockhart</surname><given-names>GD</given-names></name>, <name><surname>Nassichuk</surname><given-names>WW</given-names></name>, <name><surname>Carlson</surname><given-names>JA</given-names></name> (<year>1999</year>) <article-title>Thermal maturity evaluation of dispersed organic matter inclusions from kimberlite pipes, Lac de Gras, Northwest Territories, Canada</article-title>. <source>Int J Coal Geol</source><volume>40</volume>: <fpage>1</fpage>–<lpage>25</lpage></mixed-citation></ref><ref id="pone.0045537-Epstein1"><label>24</label><mixed-citation publication-type="journal"><name><surname>Epstein</surname><given-names>S</given-names></name>, <name><surname>Thompson</surname><given-names>P</given-names></name>, <name><surname>Yapp</surname><given-names>CJ</given-names></name> (<year>1977</year>) <article-title>Oxygen and hydrogen isotopic ratios in plant cellulose</article-title>. <source>Science</source><volume>198</volume>: <fpage>1209</fpage>–<lpage>1215</lpage><pub-id pub-id-type="pmid">17741685</pub-id></mixed-citation></ref><ref id="pone.0045537-West1"><label>25</label><mixed-citation publication-type="journal"><name><surname>West</surname><given-names>JB</given-names></name>, <name><surname>Sobek</surname><given-names>A</given-names></name>, <name><surname>Ehleringer</surname><given-names>JR</given-names></name> (<year>2008</year>) <article-title>A simplified GIS approach to modeling global leaf water isoscapes</article-title>. <source>PLoS ONE</source><volume>3</volume>: <fpage>e2447</fpage><pub-id pub-id-type="pmid">18560592</pub-id></mixed-citation></ref><ref id="pone.0045537-Pagani1"><label>26</label><mixed-citation publication-type="journal"><name><surname>Pagani</surname><given-names>M</given-names></name>, <name><surname>Pedentchouk</surname><given-names>N</given-names></name>, <name><surname>Huber</surname><given-names>M</given-names></name>, <name><surname>Sluijs</surname><given-names>A</given-names></name>, <name><surname>Schouten</surname><given-names>S</given-names></name>, <etal>et al</etal> (<year>2006</year>) <article-title>Arctic hydrology during global warming at the Palaeocene-Eocene thermal maximum</article-title>. <source>Nature</source><volume>442</volume>: <fpage>671</fpage>–<lpage>675</lpage><pub-id pub-id-type="pmid">16906647</pub-id></mixed-citation></ref><ref id="pone.0045537-Byrne1"><label>27</label><mixed-citation publication-type="other">Byrne MC (2005) A stable isotope stratigraphy for the Axel Heiberg fossil forest and its application to Eocene climate. MSc thesis, Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA. 184 p.</mixed-citation></ref><ref id="pone.0045537-McKellar1"><label>28</label><mixed-citation publication-type="journal"><name><surname>McKellar</surname><given-names>RC</given-names></name>, <name><surname>Wolfe</surname><given-names>AP</given-names></name>, <name><surname>Tappert</surname><given-names>R</given-names></name>, <name><surname>Muehlenbachs</surname><given-names>K</given-names></name> (<year>2008</year>) <article-title>Correlation of Grassy Lake and Cedar Lake ambers using infrared spectroscopy, stable isotopes, and palaeoentomology</article-title>. <source>Can J Earth Sci</source><volume>45</volume>: <fpage>1061</fpage>–<lpage>1082</lpage></mixed-citation></ref><ref id="pone.0045537-Chikaraishi1"><label>29</label><mixed-citation publication-type="journal"><name><surname>Chikaraishi</surname><given-names>Y</given-names></name>, <name><surname>Naraoka</surname><given-names>H</given-names></name>, <name><surname>Poulson</surname><given-names>SR</given-names></name> (<year>2004</year>) <article-title>Carbon and hydrogen isotopic fractionation during lipid biosynthesis in a higher plant (<italic>Cryptomeria japonica</italic>)</article-title>. <source>Phytochemistry</source><volume>65</volume>: <fpage>323</fpage>–<lpage>330</lpage><pub-id pub-id-type="pmid">14751303</pub-id></mixed-citation></ref><ref id="pone.0045537-Gonzalez1"><label>30</label><mixed-citation publication-type="journal"><name><surname>Gonzalez</surname><given-names>G</given-names></name>, <name><surname>Tappert</surname><given-names>R</given-names></name>, <name><surname>Wolfe</surname><given-names>AP</given-names></name>, <name><surname>Muehlenbachs</surname><given-names>K</given-names></name> (<year>2012</year>) <article-title>Deuterium isotopic exchangeability of resin and amber at low thermal stress under hydrous conditions</article-title>. <source>European Geophysical Union General Assembly, Vienna, Geophysical Research Abstracts</source><volume>14</volume>: <fpage>EGU2012</fpage>–<lpage>6836-2</lpage></mixed-citation></ref><ref id="pone.0045537-Jahren1"><label>31</label><mixed-citation publication-type="journal"><name><surname>Jahren</surname><given-names>AH</given-names></name>, <name><surname>Sternberg</surname><given-names>LSL</given-names></name> (<year>2002</year>) <article-title>Eocene meridional weather patterns reflected in the oxygen isotopes of Arctic fossil wood</article-title>. <source>GSA Today</source><volume>12</volume>: <fpage>4</fpage>–<lpage>9</lpage></mixed-citation></ref><ref id="pone.0045537-Lipp1"><label>32</label><mixed-citation publication-type="journal"><name><surname>Lipp</surname><given-names>J</given-names></name>, <name><surname>Trimborn</surname><given-names>P</given-names></name>, <name><surname>Fritz</surname><given-names>P</given-names></name>, <name><surname>Moser</surname><given-names>H</given-names></name>, <name><surname>Becker</surname><given-names>B</given-names></name>, <etal>et al</etal> (<year>1991</year>) <article-title>Stable isotopes in tree-ring cellulose and climatic change</article-title>. <source>Tellus</source><volume>43B</volume>: <fpage>322</fpage>–<lpage>330</lpage></mixed-citation></ref><ref id="pone.0045537-Jahren2"><label>33</label><mixed-citation publication-type="journal"><name><surname>Jahren</surname><given-names>AH</given-names></name>, <name><surname>Sternberg</surname><given-names>LSL</given-names></name> (<year>2003</year>) <article-title>Humidity estimates for the middle-Eocene Arctic rainforest</article-title>. <source>Geology</source><volume>31</volume>: <fpage>463</fpage>–<lpage>466</lpage></mixed-citation></ref><ref id="pone.0045537-Eberle1"><label>34</label><mixed-citation publication-type="journal"><name><surname>Eberle</surname><given-names>JJ</given-names></name>, <name><surname>Fricke</surname><given-names>HC</given-names></name>, <name><surname>Humphrey</surname><given-names>JD</given-names></name>, <name><surname>Hackett</surname><given-names>L</given-names></name>, <name><surname>Newbrey</surname><given-names>MG</given-names></name>, <etal>et al</etal> (<year>2010</year>) <article-title>Seasonal variability in Arctic temperatures during early Eocene time</article-title>. <source>Earth Planet Sci Lett</source><volume>296</volume>: <fpage>481</fpage>–<lpage>486</lpage></mixed-citation></ref><ref id="pone.0045537-Roden1"><label>35</label><mixed-citation publication-type="journal"><name><surname>Roden</surname><given-names>JS</given-names></name>, <name><surname>Lin</surname><given-names>G</given-names></name> (<year>2000</year>) <collab>Ehleringer</collab> (<year>2000</year>) <article-title>A mechanistic model for interpretation of hydrogen and oxygen isotope ratios in tree-ring cellulose</article-title>. <source>Geochim Cosmochim Acta</source><volume>64</volume>: <fpage>21</fpage>–<lpage>35</lpage></mixed-citation></ref><ref id="pone.0045537-Anderson2"><label>36</label><mixed-citation publication-type="journal"><name><surname>Anderson</surname><given-names>WT</given-names></name>, <name><surname>Bernasconi</surname><given-names>SM</given-names></name>, <name><surname>McKenzie</surname><given-names>JA</given-names></name>, <name><surname>Saurer</surname><given-names>M</given-names></name>, <name><surname>Schweingruber</surname><given-names>F</given-names></name> (<year>2002</year>) <article-title>Model evaluation for reconstructing the oxygen isotopic composition in precipitation from tree ring cellulose over the last century</article-title>. <source>Chem Geol</source><volume>182</volume>: <fpage>121</fpage>–<lpage>137</lpage></mixed-citation></ref><ref id="pone.0045537-Fricke1"><label>37</label><mixed-citation publication-type="journal"><name><surname>Fricke</surname><given-names>HC</given-names></name>, <name><surname>Wing</surname><given-names>SL</given-names></name> (<year>2004</year>) <article-title>Oxygen isotope and paleobotanical estimates of temperature and δ<sup>18</sup>O-latitude gradients over North America during the Early Eocene</article-title>. <source>Am J Sci</source><volume>304</volume>: <fpage>612</fpage>–<lpage>635</lpage></mixed-citation></ref><ref id="pone.0045537-Environment1"><label>38</label><mixed-citation publication-type="other">Environment Canada (2009) National Climate Data and Information Archive. Available: <ext-link ext-link-type="uri" xlink:href="http://www.climate.weatheroffice.ec.gc.ca">www.climate.weatheroffice.ec.gc.ca</ext-link> Accessed 2011 July 10.</mixed-citation></ref><ref id="pone.0045537-LePage1"><label>39</label><mixed-citation publication-type="other">LePage BA, Williams CJ, Yang H (2005) The geobiology and ecology of <italic>Metasequoia</italic> Topics in Geobiology 22. Dordrecht: Springer Verlag. 434 p.</mixed-citation></ref><ref id="pone.0045537-Sluijs1"><label>40</label><mixed-citation publication-type="journal"><name><surname>Sluijs</surname><given-names>A</given-names></name>, <name><surname>Schouten</surname><given-names>S</given-names></name>, <name><surname>Donders</surname><given-names>TH</given-names></name>, <name><surname>Schoon</surname><given-names>P</given-names></name>, <name><surname>Röhl</surname><given-names>U</given-names></name>, <etal>et al</etal> (<year>2009</year>) <article-title>Warm and wet conditions in the Arctic region during Eocene Thermal Maximum 2</article-title>. <source>Nat Geosci</source><volume>2</volume>: <fpage>777</fpage>–<lpage>780</lpage></mixed-citation></ref><ref id="pone.0045537-Birks1"><label>41</label><mixed-citation publication-type="other">Birks SJ, Edwards TWD, Gibson JJ, Michel FA, Drimmie RJ, <etal>et al</etal>. (2003) Canadian Network for Isotopes in Precipitation. University of Waterloo. Available: <ext-link ext-link-type="uri" xlink:href="http://science.uwaterloo.ca/~twdedwar/cnip/cniphome.html">http://science.uwaterloo.ca/~twdedwar/cnip/cniphome.html</ext-link> Accessed 2011 Nov 3.</mixed-citation></ref><ref id="pone.0045537-Ault1"><label>42</label><mixed-citation publication-type="journal"><name><surname>Ault</surname><given-names>AK</given-names></name>, <name><surname>Flowers</surname><given-names>RM</given-names></name>, <name><surname>Bowring</surname><given-names>SA</given-names></name> (<year>2009</year>) <article-title>Phanerozoic burial and unroofing history of the western Slave craton and Wopmay orogen from apatite (U-Th)/He thermochronometry</article-title>. <source>Earth Planet Sci Lett</source><volume>284</volume>: <fpage>1</fpage>–<lpage>11</lpage></mixed-citation></ref><ref id="pone.0045537-Zachos1"><label>43</label><mixed-citation publication-type="journal"><name><surname>Zachos</surname><given-names>J</given-names></name>, <name><surname>Pagani</surname><given-names>M</given-names></name>, <name><surname>Sloan</surname><given-names>L</given-names></name>, <name><surname>Thomas</surname><given-names>E</given-names></name>, <name><surname>Billups</surname><given-names>K</given-names></name> (<year>2001</year>) <article-title>Trends, rhythms, and aberrations in global climate 65 Ma to present</article-title>. <source>Science</source><volume>292</volume>: <fpage>686</fpage>–<lpage>693</lpage><pub-id pub-id-type="pmid">11326091</pub-id></mixed-citation></ref><ref id="pone.0045537-Gaudinski1"><label>44</label><mixed-citation publication-type="journal"><name><surname>Gaudinski</surname><given-names>JB</given-names></name>, <name><surname>Dawson</surname><given-names>TE</given-names></name>, <name><surname>Quideau</surname><given-names>S</given-names></name>, <name><surname>Schuur</surname><given-names>EAG</given-names></name>, <name><surname>Roden</surname><given-names>JS</given-names></name>, <etal>et al</etal> (<year>2005</year>) <article-title>Comparative analysis of cellulose preparation techniques for use with <sup>13</sup>C, <sup>14</sup>C, and <sup>18</sup>O isotopic measurements</article-title>. <source>Anal Chem</source><volume>77</volume>: <fpage>7212</fpage>–<lpage>7224</lpage><pub-id pub-id-type="pmid">16285668</pub-id></mixed-citation></ref><ref id="pone.0045537-Sternberg1"><label>45</label><mixed-citation publication-type="other">Sternberg L (1989) Oxygen and hydrogen isotope measurements in plant cellulose analysis. In: HF Linskens, JF Jackson, eds. Modern Methods of Plant Analysis, Vol. 10: Plant Fibers. Berlin: Springer Verlag. 89–99.</mixed-citation></ref></ref-list></back></pmc></record>Pour manipuler ce document sous Unix (Dilib)
EXPLOR_STEP=$WICRI_ROOT/Wicri/Terre/explor/CobaltMaghrebV1/Data/Pmc/Corpus
HfdSelect -h $EXPLOR_STEP/biblio.hfd -nk 000448 | SxmlIndent | more
Ou
HfdSelect -h $EXPLOR_AREA/Data/Pmc/Corpus/biblio.hfd -nk 000448 | SxmlIndent | more
Pour mettre un lien sur cette page dans le réseau Wicri
{{Explor lien
|wiki= Wicri/Terre
|area= CobaltMaghrebV1
|flux= Pmc
|étape= Corpus
|type= RBID
|clé=
|texte=
}}
| This area was generated with Dilib version V0.6.32. |  |