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Spatial variability in modern brachiopod assemblages: Paleoecological and geochemical implications.

机译：现代腕足动物群落的空间变异性：古生态和地球化学意义。

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摘要

An accurate understanding of global patterns through geologic time depends upon multiscale analyses of spatial variation within narrow temporal intervals. This work investigates geochemical and paleoecological patterns in modern brachiopod faunas which may serve as analogues for ancient brachiopod assemblages. The paleoclimatic utility of delta18O in the phosphatic phase of lingulid brachiopod shells requires valve secretion in equilibrium with seawater, an assumption tested (and rejected) when analyzed at scales ranging from millimeters to kilometers. By contrast, biological encrustation of the brachiopod fauna of the Southeast Brazilian Bight shows strong sensitivity to microenvironmental conditions such as host identity, shape, and size, and may prove useful for studies of ancient planktonic productivity. Comparison of encrustation patterns on naturally occurring brachiopods and bivalves collected from the same sites, and occupying the same size range, demonstrates that the results of encrustation studies on modern bivalves cannot be directly applied to ancient brachiopods. However, careful comparisons may reveal patterns of epibiont selectivity and the impact of changes in the relative abundance of host shells through geologic time. Finally, neither epibiont abundance nor diversity increase with host age as indicated by dated brachiopod shells from the past 1000 years. These results suggest that the temporal resolution of epibiont assemblages matches their spatial resolution, and strengthen evidence for competition among encrusting taxa. By documenting geochemical and paleoecological variation within shells and across a continental shelf, this work demonstrates the importance of understanding spatial variation across all scales before interpreting trends through time.
机译：通过地质时间准确了解全球格局取决于对狭窄时间间隔内空间变化的多尺度分析。这项工作调查了现代腕足动物的地球化学和古生态模式，它们可以作为古代腕足动物的类似物。 delta18O在舌腕臂足壳磷酸盐相中的古气候效用要求阀门分泌物与海水保持平衡，这是在毫米到千米范围内进行分析时被测试（和拒绝）的假设。相比之下，巴西东南部腕足动物区系的生物结壳显示出对微环境条件（例如寄主身份，形状和大小）的高度敏感性，并且可能被证明对古代浮游生物生产力的研究有用。比较从相同地点采集的自然腕足类和双壳类动物的结壳模式，并且它们占据相同的大小范围，这表明现代双壳类动物的结壳研究结果不能直接应用于古代腕足类动物。但是，仔细的比较可能会揭示表观生物选择性的模式以及通过地质时间变化的宿主壳相对丰度的影响。最后，近千年来腕足动物壳表明，外生生物的丰度或多样性均不会随宿主年龄的增加而增加。这些结果表明，外生体组合的时间分辨率与其空间分辨率相匹配，并加强了壳类之间竞争的证据。通过记录壳内和整个大陆架的地球化学和古生态变化，这项工作证明了在解释随时间变化的趋势之前了解所有尺度的空间变化的重要性。

著录项

  • 作者

    Rodland, David L.;

  • 作者单位

    Virginia Polytechnic Institute and State University.;

  • 授予单位 Virginia Polytechnic Institute and State University.;
  • 学科 Paleontology.; Paleoecology.; Geochemistry.
  • 学位 Ph.D.
  • 年度 2003
  • 页码 132 p.
  • 总页数 132
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 古生物学;古生物学;地质学;
  • 关键词

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