A stable isotope stratigraphy for the Axel Heiberg Fossil Forest and its application to Eocene climate

The Eocene era was a warm, climatically dynamic transitional period between the Paleocene greenhouse world and the Oligocene icehouse world. This study details carbon and hydrogen isotopic and biomarker analyses of samples of lignite (bulk fossil leaves), wood, paleosol, and resinite from the Middle to Late Eocene age fossil forest stratigraphy on Axel Heiberg Island, Nunavut, Canada. Bulk carbon isotopes show a record of frequent, large fluctuations on the scale of the Paleocene-Eocene Thermal Maximum benthic carbon excursion of [approx.] 2.6%₀ (Zachos 1999). However, terrestrial flora are less sensitive to CO₂ fluctuations given their capacity to regulate stomatal intake and the comparatively easy diffusion of CO₂ in air. Resinites (-22.8 +/- 1.7%₀) are enriched relative to bulk lignite (-24.7 +/- 0.75%₀), and wood (-21.66 +/- 0.45%₀) is also enriched relative to bulk lignite. Both 1) a scenario of periodic methane hydrate pulses and 2) a scenario of fluctuating forest stand LAI (leaf area index) are not inconsistent with our data. Either mechanism could be responsible for large carbon isotope shifts. Higher plant input dominated the n-alkane signature. Compound-specific hydrogen isotopes in n-alkanes show a record of marked secular change, with isotopes becoming generally lighter over the time span of the stratigraphy, though punctuated by singular fluctuations as large as 32%₀.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Earth, Atmospheric, and Planetary Sciences.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Byrne, Monica C. (Monica Catherine)

Advisor dc:contributor.advisor

• Roger Summons and Julian Sachs.

• Earth, Atmospheric, and Planetary Sciences.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/33941

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/33941