Variable redox conditions as an evolutionary driver? A multi-basin comparison of redox in the middle and later Cambrian oceans (Drumian-Paibian)
Variable redox conditions as an evolutionary driver? A multi-basin comparison of redox in the middle and later Cambrian oceans (Drumian-Paibian)
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DOI：
10.1016/j.palaeo.2020.110209
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发表时间：
2021-02-02
影响因子：
3
通讯作者：
Park, Tae-Yoon S.
中科院分区：
文献类型：
--
作者：
LeRoy, Matthew A.;Gill, Benjamin C.;Park, Tae-Yoon S.
中晚寒武世（Drumian-Jiangshanian年龄，505-490 Ma）是一个独特的演化动力学仍然是一个谜。这段时间记录了异常高的动物区系周转率，在寒武纪大爆发和奥陶纪生物多样性大事件（GOBE）中看到的生物多样性迅速增加的更广泛轨迹内产生了“高原”。这一时期的海洋通常被认为比晚古生代的海洋氧化程度更低，但对海洋氧化还原结构及其对生物圈的影响的了解仍然有限。重要的是，这段时间还包括两个大的碳循环扰动-DICE和SPICE事件-这被认为涉及海洋中缺氧区域的扩张，更具体地说，涉及海洋中缺氧区域的扩张。尽管有这种假设，但在这段时间内氧化还原条件的直接表征仍然有限。在这里，我们探索这些条件下使用新的和以前发表的Fespecation数据分布在五个古大陆的七个盆地，代表了一系列的沉积条件。我们的分析表明，缺氧是深水环境的一个常见和持久的特征，在这段时间内，浅水环境中通常不存在缺氧。在SPICE期间，当这些深水缺氧条件扩展到浅水环境时，可以看到这种广泛模式的一个例外。这些缺氧条件下，占主导地位的含铁和罕见的情况下，euxinia时空局限于环境的高生产力，低碎屑沉积和高硫酸盐的可用性一般低硫酸盐的海洋。有趣的是，在这些事件中，动物的营业额集中在内陆架地区，这表明这些环境的特点的可变氧化还原条件的机械联系。更广泛地说，这种不稳定的近岸环境似乎是整个寒武纪晚期和早奥陶世的动物群周转率高的可能原因，但需要进一步详细的古生物和氧化还原这些环境的调查，以充分评估这一观点。
The middle to later Cambrian (Drumian-Jiangshanian Ages, 505-490 Ma) was a time of unique evolutionary dynamics that remain enigmatic. This interval records unusually high rates of faunal turnover that produced a "plateau" within the broader trajectory of rapidly increasing biodiversity seen across the Cambrian Explosion and Great Ordovician Biodiversification Event (GOBE). The oceans during this time are generally thought to have been less oxygenated than later in the Phanerozoic, yet knowledge of oceanic redox structure and the influence this exerted upon the biosphere remains limited. Importantly, this interval also encompasses two large carbon cycle perturbations-the DICE and SPICE events-that are thought to involve the expansion of anoxic and, more specifically euxinic regions in the ocean. Despite this supposition, direct characterization of redox conditions across this time remains limited. Here we explore these conditions using new and previously published Fespeciation data from seven basins distributed across five paleocontinents representing a range of depositional conditions. Our analysis reveals anoxia was a common and persistent feature of deeper-water environments and that it was generally absent from shallower-waters across this timespan. An exception to this broad pattern is seen during the SPICE when these deeper-water anoxic conditions expanded into shallower-water environments. These anoxic conditions were dominantly ferruginous and rare instances of euxinia were spatiotemporally limited to environments of high productivity, low clastic sedimentation and high sulfate availability within a generally low-sulfate ocean. Intriguingly, during these events faunal turnover was concentrated in inner-shelf areas suggesting a mechanistic link to the variable redox conditions characteristic of these environments. More broadly this instability in nearshore environments appears a likely cause of the high rates of faunal turnover seen across the later Cambrian and into the Early Ordovician, but further detailed paleontological and redox investigation of these environments are needed to adequately evaluate this view.