Abstract The latest Triassic was an interval of prolonged biotic extinction culminating in the end-Triassic Extinction (ETE). The ETE is now associated with a perturbation of the global carbon cycle just before the end of the Triassic that has been attributed to the extensive volcanism of the Circum-Atlantic Magmatic Province (CAMP). However, we attribute the onset of declining latest Triassic diversity to an older perturbation of the carbon cycle (δ13Corg) of global extent at or very close to the Norian/Rhaetian boundary (NRB). The NRB appears to be the culmination of stepwise biotic turnovers that characterize the latest Triassic and includes global extinctions of significant marine and terrestrial fossil groups. These biotic events across the NRB have been largely under-appreciated, yet together with a coeval disturbance of the carbon cycle were pivotal in the history of the Late Triassic. Here, we present new and published δ13Corg data from widespread sections (Italy, Greece, ODP, Australia, New Zealand, USA, Canada). These sections document a previously unknown perturbation in the carbon cycle of global extent that spanned the NRB. The disturbance extended across the Panthalassa Ocean to both sides of the Pangaean supercontinent and is recorded in both the Northern and Southern Hemispheres. The onset of stepwise Late Triassic extinctions coincides with carbon perturbation (δ13Corg) at the NRB, indicating that a combination of climatic and environmental changes impacted the biota at a global scale. The NRB event may have been triggered either by gas emissions from the eruption of a large igneous province pre-dating the NRB, by a bolide impact of significant size or by some alternative source of greenhouse gas emissions. As yet, it has not been possible to clearly determine which of these trigger scenarios was responsible; the evidence is insufficient to decisively identify the causal mechanism and merits further study.

中文翻译：

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Norian/Rhaetian 边界的晚三叠世灭绝：生物证据和地球化学分析

摘要 最新的三叠纪是一段长期的生物灭绝期，最终达到三叠纪末期灭绝（ETE）。ETE 现在与三叠纪结束前全球碳循环的扰动有关，这归因于环大西洋岩浆区 (CAMP) 的广泛火山活动。然而，我们将最近三叠纪多样性下降的开始归因于全球范围内或非常接近诺里安/雷蒂安边界（NRB）的碳循环（δ13Corg）的较旧扰动。NRB 似乎是最近三叠纪特征的逐步生物更替的顶点，包括重要的海洋和陆地化石群的全球灭绝。整个 NRB 的这些生物事件在很大程度上被低估了，然而，与碳循环的同时期扰动一起，在晚三叠世的历史中起到了关键作用。在这里，我们展示了来自广泛地区（意大利、希腊、ODP、澳大利亚、新西兰、美国、加拿大）的新的和已发布的 δ13Corg 数据。这些部分记录了跨越 NRB 的全球范围碳循环中以前未知的扰动。扰动横跨泛塔拉萨洋延伸到盘古超大陆的两侧，并在北半球和南半球都有记录。晚三叠世逐步灭绝的开始与 NRB 的碳扰动 (δ13Corg) 一致，表明气候和环境变化的结合在全球范围内影响了生物群。NRB 事件可能是由 NRB 之前的大型火成岩省喷发的气体排放引发的，由巨大的火流星撞击或某些温室气体排放的替代来源造成的。到目前为止，还无法明确确定哪些触发场景是负责任的；证据不足以决定性地确定因果机制，值得进一步研究。