Calibration of the phosphate δ18O thermometer with carbonate-water oxygen isotope fractionation equations

C. Lécuyer, R. Amiot, A. Touzeau, Julie Trotter

    Research output: Contribution to journalArticle

    62 Citations (Scopus)

    Abstract

    There are significant ambiguities concerning the accuracy of oxygen isotope fractionation equations commonly used to retrieve aquatic paleotemperatures from the δ18O value of phosphatic skeletal remains. This is mainly due to the lack of a certified phosphate standard value, discrepancies in measured standard values between laboratories, and differences in methodologies used to constrain phosphate-water fractionation. Depending on the equation used, differences in calculated isotopic water temperatures may range from 4 to 8°C, these sizable uncertainties significantly reducing the effectiveness of the phosphate 18O/16O ratio as a proxy for water temperature. To address this problem, several phosphate-water fractionation equations from the literature have been tested against the well constrained oxygen isotope fractionation between calcium carbonate and water. Temperatures derived from several pairs of present-day (brachiopods) and fossil (ammonites, brachiopods, belemnite) co-existing carbonate-secreting invertebrates and phosphate-secreting vertebrates (fish) are compared to elucidate the most accurate phosphate-water fractionation equation. These temperatures were obtained by considering using a δ18O value close to 21.7‰ (VSMOW) for the reference phosphorite SRM 120c. The temperature difference (δT) calculated from various carbonate-water and phosphate-water oxygen isotope fractionation equations consistently show that the proposed phosphate-water temperature scale established using both modern lingulids and sharks, T(°C)=117.4(±9.5)-4.50(±0.43)*(δ18OPO4-δ18OH2O), consistently yields temperatures from bioapatites equivalent to those from co-existing carbonates. Compared to other published phosphate-water fractionation equations, this new equation provides the most reliable estimates of aquatic paleotemperatures for bioapatites. © 2013 Elsevier B.V.
    Original languageEnglish
    Pages (from-to)217-226
    JournalChemical Geology
    Volume347
    DOIs
    Publication statusPublished - 2013

    Fingerprint

    Oxygen Isotopes
    Thermometers
    Carbonates
    Fractionation
    oxygen isotope
    fractionation
    Phosphates
    phosphate
    Calibration
    calibration
    carbonate
    Water
    water
    water temperature
    paleotemperature
    brachiopod
    Temperature
    temperature
    belemnite
    skeletal remains

    Cite this

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    abstract = "There are significant ambiguities concerning the accuracy of oxygen isotope fractionation equations commonly used to retrieve aquatic paleotemperatures from the δ18O value of phosphatic skeletal remains. This is mainly due to the lack of a certified phosphate standard value, discrepancies in measured standard values between laboratories, and differences in methodologies used to constrain phosphate-water fractionation. Depending on the equation used, differences in calculated isotopic water temperatures may range from 4 to 8°C, these sizable uncertainties significantly reducing the effectiveness of the phosphate 18O/16O ratio as a proxy for water temperature. To address this problem, several phosphate-water fractionation equations from the literature have been tested against the well constrained oxygen isotope fractionation between calcium carbonate and water. Temperatures derived from several pairs of present-day (brachiopods) and fossil (ammonites, brachiopods, belemnite) co-existing carbonate-secreting invertebrates and phosphate-secreting vertebrates (fish) are compared to elucidate the most accurate phosphate-water fractionation equation. These temperatures were obtained by considering using a δ18O value close to 21.7‰ (VSMOW) for the reference phosphorite SRM 120c. The temperature difference (δT) calculated from various carbonate-water and phosphate-water oxygen isotope fractionation equations consistently show that the proposed phosphate-water temperature scale established using both modern lingulids and sharks, T(°C)=117.4(±9.5)-4.50(±0.43)*(δ18OPO4-δ18OH2O), consistently yields temperatures from bioapatites equivalent to those from co-existing carbonates. Compared to other published phosphate-water fractionation equations, this new equation provides the most reliable estimates of aquatic paleotemperatures for bioapatites. {\circledC} 2013 Elsevier B.V.",
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    Calibration of the phosphate δ18O thermometer with carbonate-water oxygen isotope fractionation equations. / Lécuyer, C.; Amiot, R.; Touzeau, A.; Trotter, Julie.

    In: Chemical Geology, Vol. 347, 2013, p. 217-226.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - Calibration of the phosphate δ18O thermometer with carbonate-water oxygen isotope fractionation equations

    AU - Lécuyer, C.

    AU - Amiot, R.

    AU - Touzeau, A.

    AU - Trotter, Julie

    PY - 2013

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    N2 - There are significant ambiguities concerning the accuracy of oxygen isotope fractionation equations commonly used to retrieve aquatic paleotemperatures from the δ18O value of phosphatic skeletal remains. This is mainly due to the lack of a certified phosphate standard value, discrepancies in measured standard values between laboratories, and differences in methodologies used to constrain phosphate-water fractionation. Depending on the equation used, differences in calculated isotopic water temperatures may range from 4 to 8°C, these sizable uncertainties significantly reducing the effectiveness of the phosphate 18O/16O ratio as a proxy for water temperature. To address this problem, several phosphate-water fractionation equations from the literature have been tested against the well constrained oxygen isotope fractionation between calcium carbonate and water. Temperatures derived from several pairs of present-day (brachiopods) and fossil (ammonites, brachiopods, belemnite) co-existing carbonate-secreting invertebrates and phosphate-secreting vertebrates (fish) are compared to elucidate the most accurate phosphate-water fractionation equation. These temperatures were obtained by considering using a δ18O value close to 21.7‰ (VSMOW) for the reference phosphorite SRM 120c. The temperature difference (δT) calculated from various carbonate-water and phosphate-water oxygen isotope fractionation equations consistently show that the proposed phosphate-water temperature scale established using both modern lingulids and sharks, T(°C)=117.4(±9.5)-4.50(±0.43)*(δ18OPO4-δ18OH2O), consistently yields temperatures from bioapatites equivalent to those from co-existing carbonates. Compared to other published phosphate-water fractionation equations, this new equation provides the most reliable estimates of aquatic paleotemperatures for bioapatites. © 2013 Elsevier B.V.

    AB - There are significant ambiguities concerning the accuracy of oxygen isotope fractionation equations commonly used to retrieve aquatic paleotemperatures from the δ18O value of phosphatic skeletal remains. This is mainly due to the lack of a certified phosphate standard value, discrepancies in measured standard values between laboratories, and differences in methodologies used to constrain phosphate-water fractionation. Depending on the equation used, differences in calculated isotopic water temperatures may range from 4 to 8°C, these sizable uncertainties significantly reducing the effectiveness of the phosphate 18O/16O ratio as a proxy for water temperature. To address this problem, several phosphate-water fractionation equations from the literature have been tested against the well constrained oxygen isotope fractionation between calcium carbonate and water. Temperatures derived from several pairs of present-day (brachiopods) and fossil (ammonites, brachiopods, belemnite) co-existing carbonate-secreting invertebrates and phosphate-secreting vertebrates (fish) are compared to elucidate the most accurate phosphate-water fractionation equation. These temperatures were obtained by considering using a δ18O value close to 21.7‰ (VSMOW) for the reference phosphorite SRM 120c. The temperature difference (δT) calculated from various carbonate-water and phosphate-water oxygen isotope fractionation equations consistently show that the proposed phosphate-water temperature scale established using both modern lingulids and sharks, T(°C)=117.4(±9.5)-4.50(±0.43)*(δ18OPO4-δ18OH2O), consistently yields temperatures from bioapatites equivalent to those from co-existing carbonates. Compared to other published phosphate-water fractionation equations, this new equation provides the most reliable estimates of aquatic paleotemperatures for bioapatites. © 2013 Elsevier B.V.

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    DO - 10.1016/j.chemgeo.2013.03.008

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