The sedimentological and geochemical expression of Mesozoic ocean anoxic events (OAEs) in the geologic record is reasonably well-characterized and the causal mechanisms driving these events are generally agreed upon. By contrast, OAE-type intervals in the Paleozoic are relatively understudied and less well constrained. Here, we review literature published on three intervals that may be termed OAEs in the Paleozoic: the Late Cambrian Steptoean Positive Carbon Isotope Excursion (SPICE) event, the Late Ordovician – Early Silurian Hirnantian Ocean Anoxic Event (HOAE), and the Late Devonian Frasnian-Famennian, or Kellwasser events. Comparing them to Mesozoic OAEs reveals that Paleozoic OAEs are typically longer in duration than Mesozoic OAEs, and it is also likely that anoxic waters were more areally extensive during these Paleozoic events. With the traditional framework for OAEs the potential for a very extended timeframe of anoxia is problematic, given that more extensive bottom-water anoxia should accelerate reoxygenation of the atmosphere-ocean by promoting more efficient phosphorous recycling in the ocean and therefore boosting primary productivity. However, benthic phosphorous retention could have been enhanced under anoxic and iron-rich (ferruginous) marine conditions. Therefore, we propose a role for ferruginous conditions with more widespread anoxia in driving longer OAEs. Ultimately, a protracted increase in atmospheric oxygen concentrations through the Phanerozoic may have been a key factor controlling the expression of OAEs through time.

地质记录中中生代海洋缺氧事件 (OAE) 的沉积学和地球化学表现得到了合理的表征，并且普遍同意驱动这些事件的因果机制。相比之下，古生界的 OAE 型层段研究相对较少，限制也较少。在这里，我们回顾了在古生代可能被称为 OAE 的三个区间发表的文献：晚寒武纪 Steptoean 正碳同位素偏移 (SPICE) 事件、晚奥陶世 - 早志留世 Hirnantian 海洋缺氧事件 (HOAE) 和晚泥盆世弗拉斯-Famennian 或 Kellwasser 事件。将它们与中生代 OAE 进行比较表明，古生代 OAE 的持续时间通常比中生代 OAE 更长，而且在这些古生代事件期间，缺氧水域的面积也可能更大。考虑到更广泛的底水缺氧应该通过促进海洋中更有效的磷循环从而提高初级生产力，从而加速大气-海洋的再氧化，对于 OAE 的传统框架来说，很长一段时间缺氧的可能性是有问题的。然而，在缺氧和富含铁（铁质）的海洋条件下，底栖磷的保留可能会得到增强。因此，我们建议缺氧更广泛的铁质条件在驱动更长的 OAE 中发挥作用。最终，通过显生宙大气氧浓度的长期增加可能是控制 OAE 随时间表达的关键因素。鉴于更广泛的底水缺氧应通过促进海洋中更有效的磷循环从而提高初级生产力来加速大气-海洋的再氧化。然而，在缺氧和富含铁（铁质）的海洋条件下，底栖磷的保留可能会得到增强。因此，我们建议缺氧更广泛的铁质条件在驱动更长的 OAE 中发挥作用。最终，通过显生宙大气氧浓度的长期增加可能是控制 OAE 随时间表达的关键因素。鉴于更广泛的底水缺氧应通过促进海洋中更有效的磷循环从而提高初级生产力来加速大气-海洋的再氧化。然而，在缺氧和富含铁（铁质）的海洋条件下，底栖磷的保留可能会得到增强。因此，我们建议缺氧更广泛的铁质条件在驱动更长的 OAE 中发挥作用。最终，通过显生宙大气氧浓度的长期增加可能是控制 OAE 随时间表达的关键因素。在缺氧和富含铁（铁质）的海洋条件下，底栖磷的保留可能会增加。因此，我们建议缺氧更广泛的铁质条件在驱动更长的 OAE 中发挥作用。最终，通过显生宙大气氧浓度的长期增加可能是控制 OAE 随时间表达的关键因素。在缺氧和富含铁（铁质）的海洋条件下，底栖磷的保留可能会增加。因此，我们建议缺氧更广泛的铁质条件在驱动更长的 OAE 中发挥作用。最终，通过显生宙大气氧浓度的长期增加可能是控制 OAE 随时间表达的关键因素。