Brachiopod taxa and shell portions reliably recording past ocean environments: Toward establishing a robust paleoceanographic proxy

Kazuyuki Yamamoto, Ryuji Asami, Yasufumi Iryu

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

Fossils of rhynchonelliform brachiopods (marine invertebrates) constitute ∼70% of the samples used for delineating a well-known Phanerozoic trend in oxygen isotope composition (δ18O) of low-Mg calcite shells. The trend represents secular variations in temperature and/or δ18O of ancient seawater. However, the use of brachiopods as a paleoceanographic proxy is based on the presupposition that the shell calcite is precipitated in isotopic equilibrium with ambient seawater. Here, we show that high-resolution time series of the shell δ18O values along the maximum growth axes of two long-lived cool-water brachiopods are identical to, greater than, or less than those of calcite precipitated in isotopic equilibrium with ambient seawater, depending on the difference in shell growth rates. Coupled with δ18O data from subtropical and warm-temperate brachiopod species examined in our previous studies, we provide a sound framework illustrating which taxa and shell portions reliably recorded past ocean environments.

Original languageEnglish
Article numberL13601
JournalGeophysical Research Letters
Volume38
Issue number13
DOIs
Publication statusPublished - 2011 Jul 1

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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