Asynchronous trilobite extinctions at the early to middle Cambrian transition
Asynchronous trilobite extinctions at the early to middle Cambrian transition
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DOI：
10.1130/g46913.1
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发表时间：
2020-05
期刊：
影响因子：
5.8
通讯作者：
F. Sundberg;K. Karlstrom;G. Geyer;J. R. Foster;J. Hagadorn;M. T. Mohr;M. Schmitz;C. Dehler;L. Crossey
中科院分区：
文献类型：
--
作者：
F. Sundberg;K. Karlstrom;G. Geyer;J. R. Foster;J. Hagadorn;M. T. Mohr;M. Schmitz;C. Dehler;L. Crossey
三叶虫在寒武纪出现并迅速多样化，但其辐射和扩散是全球同步的还是地理限制和穿时的，一直存在争议。早寒武世的结束是一个典型的例子--它传统上被定义为olenellid和redlichiid三叶虫的灭绝和paradoxidid三叶虫的出现。在这里，我们将这三个三叶虫群的全球生物地层学与高精度凝灰岩和串联碎屑锆石U-Pb年龄的限制，以伪造这些事件的全球同步性先前的模型。首次，我们证明了在Laurentia的olenellid三叶虫在阿瓦隆尼亚和西冈瓦纳的paradoxidids首次出现后至少3 Ma灭绝。509 Ma）。它们也消失在雷德利基类灭绝之前和大约在苗岭阶基底之前。506 Ma，华南地区。这表明这三个三叶虫群（paradoxidids，olenellids和redlichiids）及其相关的biobacteria在时间上重叠了近40%的寒武纪2世，年龄4。这种时间重叠的含义是：（1）三叶虫的过渡是渐进的，地理介导的，而不是全球同步的;（2）古生物数据库低估了早期寒武纪的多样性。这103马的穿时性，在动物早期进化的关键时刻，也影响化学地层和古气候数据集，与三叶虫生物地层学，共同巩固我们的理解寒武纪地球系统。
Trilobites appeared and diversified rapidly in the Cambrian, but it is debated as to whether their radiations and extinctions were globally synchronous or geographically restricted and diachronous. The end of the early Cambrian is a classic example—it has traditionally been defined by the extinction of olenellid and redlichiid trilobites and the appearance of paradoxidid trilobites. Here we integrate the global biostratigraphy of these three trilobite groups with high-precision tuff and tandem detrital zircon U-Pb age constraints to falsify prior models for global synchronicity of these events. For the first time, we demonstrate that olenellid trilobites in Laurentia went extinct at least 3 Ma after the first appearance of paradoxidids in Avalonia and West Gondwana (ca. 509 Ma). They also disappeared before the extinction of redlichiids and prior to the base of the Miaolingian at ca. 506 Ma in South China. This indicates that these three trilobite groups (paradoxidids, olenellids, and redlichiids) and their associated biotas overlapped in time for nearly 40% of Cambrian Epoch 2, Age 4. Implications of this chronological overlap are: (1) trilobite transitions were progressive and geographically mediated rather than globally synchronous; and (2) paleontological databases underestimate the diversity of the early Cambrian. This ∼3 Ma diachroneity, at a critical time in the early evolution of animals, also impacts chemostratigraphic and paleoclimatic data sets that are tied to trilobite biostratigraphy and that collectively underpin our understanding of the Cambrian Earth system.