Aminostratigraphy and Ages of Pleistocene Limestones of Bermuda

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The Pleistocene stratigraphy of Bermuda offers important information for sea-level history. Corals are rare in Bermuda Pleistocene carbonates, and so many deposits are not appropriate for U-series dating. We have extended the geochronological base in Bermuda by determining the extent of isoleucine epimerization (A/I ratios) in (1) marine shells ("Glycymeris" and others) from deposits of sea-level high stands, (2) land snails ("Poecilozonites") from protosols associated with the eolianites that comprise the bulk of Bermuda, and (3) whole-rock samples of bioclastic calcarenites. The three distinct types of samples provide independent aminostratigraphies (Aminozones C, E, F, G, H, J, and K) that are mutually consistent and in agreement with the mapped lithostratigraphy. Correlation of the amino acid ratios with ages based on previously published U-series coral dates verifies the utility of the apparent parabolic kinetics model for estimation of amino acid racemization ages. Extrapolation of ages based on the model to deposits beyond the range of U-series dating reveals that a significant middle Pleistocene section is present in Bermuda.

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Geological Society of America Bulletin, v. 104, issue 4, p. 471-480

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