Enhancing the Fidelity of Early Paleogene Planktic Foraminiferal Oxygen Isotope and Mg/Ca Records with the Use of In Situ Analytical Techniques

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Funds are provided for the continued development and testing of a new technique for acquiring reliable delta 18O data from slightly to moderately altered planktic shells preserved in deep-sea sediments. This technique uses a secondary ion mass spectrometer (SIMS) for in situ delta 18O analysis of domains within individual planktic shells recovered from Early Paleogene deep-sea records. Initial results confirm the veracity of this approach suggesting that it will be transformative for quantifying and circumventing the effects of diagenesis on 18O obtained from planktic shells. Paired delta 18O values with Mg/Ca ratios in the same planktic shell will be used to reconstruct Early Paleogene variation in SSTs and seawater delta 18O at tropical (Site 865) and subpolar (Site 690) latitudes. The basal areas of pustular outgrowths (muricae) on their chamber walls represent domains of enhanced biocalcification that contain no mural pores, making them less susceptible to diagenesis and ideal targets for SIMS. Objectives of this proposal are threefold: (1) Reassess tropical open-ocean SSTs during the Early Paleogene. (2) Quantify the effects of diagenesis on paleoceanographic proxies. (3) Compare low- and high-latitude records with emphasis on transient hyperthermal climate states.Broader Impacts: The method, when widely applicable, could transform the study of paleoclimates based of planktic foraminiferal delta 18O. The study of Early Paleogene greenhouse climate could be an analog for future climate change driven by fossil fuel emissions.