Calibrating Diatom Oxygen Isotopes for Paleoceanographic Applications Using a Novel Technique

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The oxygen isotopic composition (delta18O) of silicate in diatom tests has the potential to deliver key paleoceanographic information, but is underutilized because of the difficulty associated with isolating it for geochemical analysis. This work will refine and apply a new technique ("microfluorination") that has the potential to make d18O in diatoms a more routine measurement. A suite of experiments will be conducted to improve the efficiency of the technique and reduce the sample size required for analysis. The technique will then be applied to cultured marine and freshwater diatoms in order to calibrate the proxy relationship between diatom delta18O and temperature. Finally, diatoms from a sediment trap and boxcore collected in the Guaymas Basin will be analyzed to a) constrain biomineralization depth, b) compare oxygen isotope data between diatoms and foraminifera, and c) assess diagenetic effects on diatom delta18O data. Developing the microfluorination technique and the diatom delta18O-temperature proxy relationship will enable scientists to tap an important, underexploited source of information about ocean-climate dynamics. The project will support a PhD student and provide training opportunities in a state-of-the-art technique for undergraduate students and future post-doctoral researchers in the PI's lab. Project results will be incorporated into graduate coursework. This research will strengthen international ties via collaboration with investigators in the UK and Germany.