The early Paleozoic was marked by several carbon-cycle perturbations and associated carbon-isotope excursions (CIEs). Whether these CIEs are connected to significant (external) triggers, as is commonly considered to be the case for CIEs in the Mesozoic and Cenozoic, or result from small carbon-cycle imbalances that became amplified through lack of efficient silicate weathering or other feedbacks remains unclear. We present concentration and isotope data for sedimentary mercury (Hg) and osmium (Os) to assess the impact of subaerial and submarine volcanism and weathering during the late Cambrian and early Ordovician. Data from the Alum Shale Formation (Sweden) cover the Steptoean positive carbon-isotope excursion (SPICE; ca. 497–494 Ma), a period marked by marine anoxia and biotic overturning, and several smaller CIEs extending into the early Ordovician. Our Hg and Os data offer no strong evidence that the CIEs present in our record were driven by (globally) elevated volcanism or continental weathering. Organic-carbon and Hg concentrations covary cyclically, providing further evidence of an unperturbed Hg cycle. Mesozoic and Cenozoic CIEs are commonly linked to enhanced volcanic activity and weathering, but similar late Cambrian–early Ordovician events cannot easily be connected to such external triggers. Our results are more consistent with reduced early Paleozoic carbon-cycle resilience that allowed small imbalances to develop into large CIEs.

中文翻译：

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没有证据表明火山引发晚寒武世碳循环扰动

早古生代的特点是几次碳循环扰动和相关的碳同位素漂移（CIE）。这些 CIE 是否与重要的（外部）触发因素有关（通常被认为是中生代和新生代的 CIE 的情况），还是由于缺乏有效的硅酸盐风化或其他反馈而放大​​的小型碳循环失衡所致，目前尚不清楚。我们提供沉积物汞 (Hg) 和锇 (Os) 的浓度和同位素数据，以评估寒武纪晚期和奥陶纪早期陆地和海底火山活动和风化的影响。来自 Alum 页岩地层（瑞典）的数据涵盖了 Steptoean 碳同位素正偏移（SPICE；约 497-494 Ma），这是一个以海洋缺氧和生物翻转为标志的时期，以及几个延伸至奥陶纪早期的较小 CIE。我们的汞和锇数据没有提供强有力的证据表明我们记录中出现的 CIE 是由（全球）火山活动加剧或大陆风化引起的。有机碳和汞浓度周期性共变，进一步证明汞循环不受干扰。中生代和新生代 CIE 通常与火山活动和风化作用增强有关，但类似的晚寒武世 - 早奥陶世事件很难与此类外部触发因素联系起来。我们的结果与早期古生代碳循环弹性的降低更加一致，这种弹性使得小的不平衡发展成大型的 CIE。