Development of New Techniques: Sustaining and sharpening amino acid geochronology

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Determining the ages of geological materials (geochronology) is fundamental to understanding Earth's history. Amino acid racemization (AAR) geochronology is a dating method applicable to a wide range of fossils types, depositional environments, and time scales. It enables research in a broad range of geoscience topics such as archeology, historical ecology, paleontology, tectonic geomorphology, paleoceanography, glacial geology, and others. This award will support scientific infrastructure by sustaining the laboratory for AAR geochronology at Northern Arizona University. This project will sharpen one of the most outstanding untapped applications of AAR geochronology: as a dating method for marine sediment cores using foraminifera. Various procedures will be tested to reduce analytical variability, a major source of error for AAR geochronology when applied to foraminifera. Several widely occurring foraminifera taxa will be subjected to chemical pre-treatments to isolate a fraction of amino acids that is less prone to post-depositional environmental influences. Once optimized, the treatment will be applied to samples from a network of stratigraphic reference horizons from well-dated deep-sea cores. The data will be used to evaluate the reproducibility of AAR geochronology among the sites and to calibrate the rate of racemization for several reference species. Samples from other sites will be used to quantify the possible influence of different geothermal gradients on the extent of racemization in foraminifera. Recently developed data-analytical approaches will be employed to model the time-dependent rate of racemization and to characterize age uncertainties.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.