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J. Garrecht Metzger
Washington University in St. Louis
Earth and Planetary Sciences
Advisor: Assistant Professor David Fike
Abstract
The Ordovician contains the largest radiation (diversification) in marine animals as well as the Hirnantian extinction, the first of five mass extinctions of the Phanerozoic. Changes in the stable isotopic compositions of coeval sediments are central for reconstructing changes in paleoenvironmental chemistry that likely altered the course of Earth and animal history. Coeval trends in S and C isotopes will be used to understand the possible linkages between the biogeochemical C and S cycles as well as understanding the relationship between global environmental change and biological radiation. Two Lower Ordovician cores from west-central Texas (Ellenburger formation) are being processed for the stable isotopic composition of carbonate carbon (ς13Ccarb), organic carbon (ς13Corg), carbonate associated sulfate (ς34SCAS), and pyrite (ς34Spyr). Isotopic data sets will be coupled with stratigraphic information to be used as a correlative tool for the two cores. An increase in the offset between ς13Ccarb and ς13Corg over 180m from core C23 has been interpreted to possibly result from an increase in the partial pressure of atmospheric CO2 (pCO2), however further work must be done to test the robustness of this interpretation. Future work will utilize isotopic mass-balance models across both cores to develop plausible mechanisms for the observed isotopic trends. These data sets will be an essential tool for explaining the timing, duration, and nature of the Ordovician Radiation. Life on other planets may presumable produce similar geochemical changes and terrestrial elucidation of causal mechanisms will function as a useful biogeochemical reference.
David McKinnon is originally from Wright City MO, and is a junior in aerospace engineering at the Missouri University of Science and Technology. He is an active participant in the AAVG design team, which competes every year at NASA's USLI competition. He hopes to work on the next generation of space access vehicles.
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