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

Abstract

Other| April 01, 2003 Resolution and Fidelity of Oxygen Isotopes as Paleotemperature Proxies in Bivalve Mollusk Shells: Models and Observations DAVID H. GOODWIN; DAVID H. GOODWIN 1Department of Geosciences, University of Arizona, Tucson, AZ, 85721, [e-mail] Search for other works by this author on: GSW Google Scholar BERND R. SCHÖNE; BERND R. SCHÖNE 1Department of Geosciences, University of Arizona, Tucson, AZ, 85721, [e-mail] * Current address: Institute for Geology and Paleontology, Increments Group, Johann Wolfgang Goethe University, D-60054 Frankfurt, Germany Search for other works by this author on: GSW Google Scholar DAVID L. DETTMAN DAVID L. DETTMAN 1Department of Geosciences, University of Arizona, Tucson, AZ, 85721, [e-mail] Search for other works by this author on: GSW Google Scholar PALAIOS (2003) 18 (2): 110–125. https://doi.org/10.1669/0883-1351(2003)18<110:RAFOOI>2.0.CO;2 Article history accepted: 15 Oct 2002 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation DAVID H. GOODWIN, BERND R. SCHÖNE, DAVID L. DETTMAN; Resolution and Fidelity of Oxygen Isotopes as Paleotemperature Proxies in Bivalve Mollusk Shells: Models and Observations. PALAIOS 2003;; 18 (2): 110–125. doi: https://doi.org/10.1669/0883-1351(2003)18<110:RAFOOI>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyPALAIOS Search Advanced Search Abstract 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 incomplete. Growth cessations and/or changing growth rates can reduce the range and resolution of the recorded environmental conditions.To investigate the effects of these variables on geochemical profiles, stable oxygen isotope (δ18O) 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 bivalve mollusk Chione cortezi. In both sets of models, multi-year δ18O profiles were calculated assuming that the bivalve shell grows continuously throughout its life. Other profiles were calculated to simulate an ontogenetic decrease in growth rate by decreasing the growth period, daily growth rate, or both. Altering the growth period simulates the effects of thermal thresholds, above or below which no shell material is deposited. Decreasing the daily growth rate results in lower annual shell growth rates while keeping the growth period constant. Combining the two provides a more accurate representation of bivalve shell growth in many subtropical and temperate species.In addition to the modeling exercise, the shell of a Chione cortezi that lived in the northern Gulf of California was sampled in two ways. First, low-resolution (300 micron) samples were recovered from the entire growth profile along the axis of maximum shell height (umbo to the commissure). Second, high-resolution (50 micron) samples were taken from regions of the shell representing winter growth from late in the bivalve's life.Modeling results and observations indicate that the fullest range of environmental conditions only is reflected in the earliest years of growth; profiles from successive years have reduced amplitudes, sample resolutions, or both. Variation of intra-annual growth rate in models simulating continuous growth can produce cuspate δ18O profiles that mimic shutdowns. More detailed sampling in later stages of ontogeny can reconstruct a fuller range of environmental conditions. Finally, within-shell trends in isotopic amplitudes and averages may reflect decreases in growth rate rather than environmental fluctuations. Therefore, particular care should be taken when interpreting inter-annual isotope profiles from long-lived species. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.