Resolution and Fidelity of Oxygen Isotopes as Paleotemperature Proxies in Bivalve Mollusk Shells: Models and Observations

Bivalve mollusks are biological chart recorders: their shells contain a record of environmental conditions in the form of geochemical variation. However, these records are often in-complete. Growth cessations and/or changing growth rates can reduce the range and resolution of the recorded environ-mental conditions. To investigate the effects of these variables on geochemical profiles, stable oxygen isotope (d18O) profiles were modeled using several growth parameters. Two sets of profiles were calculated: one with constant daily increment widths, the other based on the annual pattern of daily increment width variation observed in the northern Gulf of California bi-valve mollusk Chione cortezi. In both sets of models, multi-year d18O profiles were calculated assuming that the bivalve shell grows continuously throughout its life. Other profiles