Using Mg-Paleothermometry to Deconvolute the Marine Oxygen Isotope Record

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This project will explore the utility of Mg/Ca in foraminiferal calcite as a tracer of water temperature. If Mg/Ca has a consistent correlation with water temperature and is not subject to complications such as physiologic fractionation or post-depositional diagenesis, it can be used in conjunction with 18 O/16 O to estimate sea surface temperature and mean ocean composition as a function of ice volume, allowing the determination of two important variables in the geologic past. Paired analyses of Mg/Ca and 18 O/16 O will be done on various sample sets to test for effects of (1) species-specific fractionation, (2) growth-rate, and (3) dissolution. Studies will incorporate analyses in at least two cores from the tropical Pacific over glacial/interglacial time scales to test applicaiton of the method. 13 C/12 C data generated by the same analyses will be used to evaluate the record of past ocean alkalinity and partial pressure of CO 2, using calibrations previously established in the laboratory.