Cited by 28Paleontology and Stratigraphy of FossilsGeology and Paleoclimatology ResearchCalcium Carbonate Crystallization and Inhibition

Multi-proxy assessment of brachiopod shell calcite as a potential archive of seawater temperature and oxygen isotope composition

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Letulle, Thomas, Gaspard, Danièle, Daëron, Mathieu, Arnaud-Godet, Florent, Vinçon-Laugier, Arnauld, Suan, Guillaume, Lécuyer, Christophe·2023·Biogeosciences

Published version of a preprint

Abstract

Abstract. Most of our knowledge of past seawater temperature history is based on δ18O values of calcium carbonate fossil shells. However, the determination of past temperatures using this proxy requires the knowledge of past seawater δ18O values, which is generally poorly constrained. Other paleothermometers using carbonate archives, such as Mg/Ca ratios and clumped isotopes (Δ47), have been developed to allow for paleotemperatures to be estimated independently and to allow past ocean δ18O values to be calculated using various groups of calcifying organisms. Articulated brachiopod shells are some of the most commonly used archives in studies of past oceanic geochemistry and temperature. They are abundant in the fossil record since the Cambrian, and for decades, their low Mg–calcite mineralogy has been considered relatively resistant to diagenetic alteration. Here, we investigate the potential of brachiopod shells as recorders of seawater temperatures and seawater δ18O values using new brachiopod shell geochemical data by testing multiple well-established or suggested paleothermometers applied to carbonate archives. Modern articulated brachiopod shells covering a wide range of temperatures (−1.9 to 25.5 ∘C), depths (5 to 3431 m) and salinities (33.4 to 37.0 PSU) were analysed for their stable isotope compositions (δ13C, δ18O and Δ47) and their elemental ratios (Mg/Ca, Sr/Ca, Na/Ca and Li/Ca). Our data allowed us to propose a revised oxygen isotope fractionation equation between modern-brachiopod shell calcite and seawater: (1) T = - 5.0 ( ± 0.2 ) ( δ 18 O c - δ 18 O sw ) + 19.4 ( ± 0.4 ) , where δ18Oc is in ‰ VPDB, δ18Osw is in ‰ VSMOW, and T is in ∘C. Our results strongly support the use of clumped isotopes as an alternative temperature proxy but confirm significant offsets relative to the canonical relationship established for other biogenic and abiogenic calcium carbonate minerals. Brachiopod shell Mg/Ca ratios show no relationship with seawater temperatures, indicating that this ratio is a poor recorder of past changes in temperatures, an observation at variance with several previous studies. Despite significant correlations with brachiopod living temperature, brachiopod shell Sr/Ca, Na/Ca and Li/Ca values indicate the influence of environmental and biological factors unrelated to temperature, which undermines their potential as alternative temperature proxies. Kinetic effects (growth rates) could explain most of the deviation of brachiopod shell calcite from expected isotopic equilibrium with seawater and part of the distribution of Sr/Ca, Na/Ca and Li/Ca ratios.

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Authors
Letulle, T., Gaspard, D., Daëron, M., Arnaud-Godet, F., Vinçon-Laugier, A., Suan, G., & Lécuyer, C.
Affiliations
  • Lyon 1 Université (FR)
  • Centre National de la Recherche Scientifique (FR)
Corresponding author
Letulle, Thomas
Venue
Biogeosciences
Published
2023-04-12
Volume
20
Issue
7
Pages
1381-1403
ISSN
  • 1726-4170 (ISSN-L)
  • 1726-4189
OpenAlex
W4367667821
Cited by
28
References
115
Citations by year
2026: 8 · 2025: 6 · 2024: 10 · 2023: 4
FWCI
5.66
Type
journal article
Language
en
Open access
Locations
  • Biogeosciences (publishedVersion, cc-by)
  • HAL (submittedVersion, other-oa)
  • Institutional Archive of Ifremer (French Research Institute for Exploitation of the Sea) (submittedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
Agence Nationale de la Recherche (ANR-18-CE31-0020)
Topics
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Stratigraphy of Fossils
  • Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Geology and Paleoclimatology Research
  • Physical Sciences › Materials Science › Biomaterials › Calcium Carbonate Crystallization and Inhibition
Keywords
shells, seawater temperature, oxygen isotope fractionation, clumped isotopes, paleothermometry, Mg/Ca ratio, Sr/Ca ratio, Na/Ca ratio, diagenetic alteration, carbonate geochemistry, paleoclimate proxies

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