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Geochemical evidence for widespread euxinia in the Later Cambrian ocean

机译：地球化学证据表明晚寒武世海洋中存在广泛的游动游

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摘要

Widespread anoxia in the ocean is frequently invoked as a primary driver of mass extinction as well as a long-term inhibitor of evolu-tionary radiation on early Earth. In recent biogeochemical studies it has been hypothesized that oxygen deficiency was widespread in subsurface water masses of later Cambrian oceans, possibly influ-encing evolutionary events during this time. Physical evidence of widespread anoxia in Cambrian oceans has remained elusive and thus its potential relationship to the palaeontological record remains largely unexplored. Here we present sulphur isotope records from six globally distributed stratigraphic sections of later Cambrian marine rocks (about 499 million years old). We find a positive sul-phur isotope excursion in phase with the Steptoean Positive Carbon Isotope Excursion (SPICE), a large and rapid excursion in the marine carbon isotope record, which is thought to be indicative of a global carbon cycle perturbation. Numerical box modelling of the paired carbon sulphur isotope data indicates that these isotope shifts reflect transient increases in the burial of organic carbon and pyrite sulphur in sediments deposited under large-scale anoxic and sulphidic (euxinic) conditions. Independently, molybdenum abun-dances in a coeval black shale point convincingly to the transient spread of anoxia. These results identify the SPICE interval as the best characterized ocean anoxic event in the pre-Mesozoic ocean and an extreme example of oxygen deficiency in the later Cambrian ocean. Thus, a redox structure similar to those in Proterozoic oceans may have persisted or returned in the oceans of the early Phanerozoic eon. Indeed, the environmental challenges presented by widespread anoxia may have been a prevalent if not dominant influence on animal evolution in Cambrian oceans.
机译：海洋中普遍存在的缺氧症经常被认为是导致生物大灭绝的主要驱动力，也是长期以来地球早期演化辐射的抑制剂。在最近的生物地球化学研究中，有假设认为缺氧现象在后来的寒武纪海洋的地下水体中普遍存在，可能影响这段时期的演化事件。寒武纪海洋中普遍存在的缺氧的物理证据仍然难以捉摸，因此其与古生物学记录的潜在关系仍未得到充分探索。在这里，我们介绍了晚寒武纪海相岩石（约4.99亿年的历史）的六个全球分布的地层剖面中的硫同位素记录。我们发现与正阶跃正碳同位素偏移（SPICE）同相的南苏丹同位素正偏移，这是海洋碳同位素记录中的大而快速偏移，这被认为是全球碳循环扰动的指示。配对的碳硫同位素数据的数字箱模型表明，这些同位素位移反映了在大规模缺氧和硫化（富氧）条件下沉积的沉积物中有机碳和黄铁矿硫埋藏的瞬时增加。独立地，在一个中世纪的黑色页岩中，钼的丰度明显地证明了缺氧的瞬时扩散。这些结果表明，SPICE间隔是中生代前海洋中最典型的海洋缺氧事件，也是后来寒武纪海洋中缺氧的极端例子。因此，类似于早生代海洋中的元古代海洋中的氧化还原结构可能一直存在或返回。的确，广泛的缺氧所带来的环境挑战可能对寒武纪海洋动物的进化具有普遍的影响，甚至不是主要的影响。

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  • 来源
    《Nature》 |2011年第7328期|p.80-83|共4页
  • 作者

    Benjamin C. Gill; Timothy W. Lyons; Seth A. Young; Lee R. Kump; Andrew H. Knoll; Matthew R. Saltzman;

  • 作者单位

    Department of Earth Sciences, University of California, 900 University Avenue, Riverside, California 92521, USA,Department of Earth and Planetary Sciences Harvard University, 20 Oxford Street, Cambridge, Massachusetts 02138, USA;

    Department of Earth Sciences, University of California, 900 University Avenue, Riverside, California 92521, USA;

    Department of Geological Sciences, Indiana University-Bloomington, 1001 East 10th Street, Bloomington, Indiana 47405-1405, USA;

    Department of Geosciences, Penn State University, 503 Deike Building, University Park, Pennsylvania 16802, USA;

    Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, Massachusetts 02138, USA;

    School of Earth Science, The Ohio State University, 275 Mendenhall Laboratory, 125 South Oval Mall, Columbus, Ohio 43210, USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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