Collaborative Research: Testing the Early Late Ordovician Cool Water Hypothesis

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Collaborative Research: Testing the Early Late Ordovician Cool Water Hypothesisby Achim Herrmann, Louisiana State UniversityKenneth MacLeod, University of MissouriStephen Leslie, James Madison UniversityEAR-1324954, -1323444, -1324577ABSTRACTThe Late Ordovician glaciation (LOG) is associated with the second largest mass extinction event of the Phanerozoic. It marks the end of the global warm conditions of the early Paleozoic that lasted ~150my and occurred under elevated pCO2 conditions. Considerable doubt has recently been raised with regard to the duration of the LOG, its potential driving mechanisms, and pre-glacial, long-term temperature variations. For instance approximately 15 Ma prior to LOG the North American continental plate was situated in tropical to subtropical latitudes, but sedimentological and paleontological evidence suggest a shift from deposition of warm water carbonates to deposition of cool water carbonates. It is not clear whether this sedimentological change reflects global cooling (indicating significant perturbation to the global climate system well before the Late Ordovician glaciation) or physical responses to tectonic activity with no requisite climatic implications. The projects will test competing hypotheses that try to explain this event through an extensive geochemical study. In particular, PIs will use the geochemical archive of conodont apatite (delta18O and epsilonNd) and carbonates (DELTA48, delta18O, and delta13C) to address questions about paleoceanographic conditions during the Early Late Ordovician. They expect that this research will lead 1) to clarification of potential causes for the paleontological/sedimentological changes during this interval, 2) to a better understanding of epicontinental sea circulation and an improved facies model for epicontinental low latitude carbonate platforms (for which no modern-day analogues exist), and 3) to better documentation of the temperature history of the Ordovician greenhouse interval.This research project will have active participation by undergraduate students, graduate students, and a secondary school science teacher. Therefore, the project will not only impact present university students and researchers, it will also impact future generations of students through enhancing an earth science secondary educations teacher¡¦s knowledge base and science curriculum. Data will be contributed to publicly accessible databases making them available for further research and general education in the fields of paleoclimate and paleoceanography.