Oral Qualifying Exam: Katherine Flanders, PhD Candidate, Green Chemistry Track, Chemistry Department
University of Massachusetts Boston
Department of Chemistry
Oral Qualifying Exam
Biogeochemical insight into the cause(s) of the end Permian extinction: A proposed biomarker reconstruction of the Neo-Tethys ocean
Presented by Katherine Flanders
for the PhD in Chemistry, Green Chemistry Track
Advisor: Professors Timothy Dransfield & Robyn Hannigan
Friday, May 23, 2014 | 10 AM - 11 AM
School for the Environment Conference Room | Science S01-0012
Effects of climate change such as global temperature rise, ocean acidification, and sea level rise are reshaping our environment. Reconstructing past environments provides information about Earth's climate cycles and helps us understand how ecosystems respond to perturbations in global cycles. 250 million years ago the largest extinction event in Earth's history occurred. The end Permian extinction had devastating effects on both terrestrial and marine communities, with 90% of marine species and 70% of vertebrate families becoming extinct. Causes of the event are unknown, but suggested kill hypotheses include a bolide impact, massive volcanism, global warming, sea level rise, and widespread ocean anoxia. Samples were collected from five Permian-Triassic exposures located in Spiti Valley, India representing marine continental shelf. Bulk carbon (δ13Corg) and sulfur (δ34S) isotope excursions indicate perturbations in global cycling of these elements. Trace element proxies (Ce/Ce*, Th/U, and Mg/Al) and the presence of pyrite (FeS2) suggest that the Neo-Tethys was anoxic but a lack of biostratigraphic and lithostratigraphic change in Spiti Valley exposures makes identifying the extinction interval difficult. Timing is crucial in identifying relations between this section in the Neo-Tethys ocean and other PT sections in an effort to detangle global and local conditions leading up to and during the extinction. I propose a complementary biomarker analysis, including compound-specific isotope analysis (CSIA), to answer three questions 1) Does biomarker stratigraphy at Spiti Valley record terrestrial extinction and post-event recovery? 2) Does biomarker stratigraphy record evidence of a global perturbation of the carbon cycle? 3) Do biomarkers support evidence for anoxic waters? Biomarker analysis and accompanying CSIA will be used to develop a chemostratigraphic model to constrain timing in Spiti Valley PT sections and used in concert with other geochemical proxies to characterize past environmental conditions.
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