Isotopic compositions of brachiopod shells. Toward a definitive understanding ofδ^<13> C andδ^<18> O evolution of Phanerozoic seawater

这项研究考察了现代腕足类贝壳碳和氧同位素组成的种间和种内变化，为利用腕足化石的碳和氧同位素组成(^&lt；13&gt；C和/或^&lt；18&gt；O值)替代溶解无机碳和海水温度和/或^&lt；18&gt；O值奠定了可靠的基础。采自亚热带和寒温带环境的6种现代腕足动物的~(13)&gt；C和~(18)&gt；O值的种间差异表明，生命效应的程度在不同物种之间有很大的差异。两种现代腕足类(9号和8号)腕足类的13&gt；C和18&gt；O值的种内变异表明，部分贝壳的13&gt；C和18&gt；O值变化较小，与周围海水处于同位素平衡状态的方解石相一致或接近。这些部分对于可靠地重建古代海洋环境是有用的。

This study examines inter-and intraspecific variations in carbon-and oxygen-isotope compositions(.^<13> C and.^<18> O) of modern brachiopod shells to establish sound basis to use the.^<13> C and.^<18> O values of fossil brachiopods as proxies for.^<13> C values of dissolved inorganic carbon and seawater temperature and/or.^<18> O values(.^<18> OSW). Interspecific variations in.^<13> C and.^<18> O values of six modern-brachiopod species collected from a subtropical to cool-temperate environments showed that the degree of the vital effect is highly variable among species. Intraspecific variation in.^<13> C and.^<18> O values of two modern-brachiopod species(9 and 8 specimens of Basiliola lucida and Terebratulina crossei, respectively) demonstrated that.^<13> C and.^<18> O values of some shell portions show small variations and are identical or close to those of calcite precipitated in isotopic equilibrium with the surrounding seawater. Such portions are useful to reliably reconstruct ancient ocean environments.