Testing for high-frequency (104-105 yr) glacio-and thermo-eustasy in greenhouse and transtional climates using oxygen isotopes of conodont apatite

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Testing for high-frequency glacio- and/or thermo-eustasy during greenhouse and transitional climates using oxygen isotopes of conodont apatite.Maya Elrick and Zachary SharpUniversity of New MexicoEAR-0920830ABSTRACTHigh-frequency (104-105 years) upward-shallowing carbonate cycles are common sedimentary features and are generally attributed to orbitally driven glacio-eustasy (changes in ice volume). But in warm, greenhouse conditions, glacial ice is thought not to have been significant, making this interpretation for high frequency carbonate cycles less compelling. We will evaluate the possibility that glacio-eustasy did occur in warm climates by analyzing oxygen isotope ratios of conodonts, a common fossil composed of diagenetically-resistant phosphate. Glacial ice strongly incorporates the light stable isotope of oxygen. Therefore, when large ice volumes are present (low sea level), the oxygen isotope ratio of the ocean becomes measurably heavier. The diagenetically resistant conodonts will allow us to search for this signal and address the long-debated origin of temporally persistent and widespread meter-scale carbonate cycles/parasequences, specifically whether the controversial proposal that transient ice sheets can form even in warm climatic periods is reasonable and supported by geochemical evidence. Our study will center on three greenhouse (Late Silurian, Early Devonian and Early Triassic) and one transitional (Early Mississippian) climatic mode. We plan to incorporate local middle and high school science teachers into our research project to help bring scientific inquiry into the classroom. This will be accomplished through collaboration with the Science Education Institute of the Southwest (SEIS), and by conducting a series of week-long summer workshops for professional teacher development in the sciences.