Late Ordovician mass extinction caused by volcanism, warming, and anoxia, not cooling and glaciation
Late Ordovician mass extinction caused by volcanism, warming, and anoxia, not cooling and glaciation
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DOI：
10.1130/g47377.1
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发表时间：
2020-08-01
期刊：
影响因子：
5.8
通讯作者：
Grasby, Stephen E.
中科院分区：
文献类型：
--
作者：
Bond, David P. G.;Grasby, Stephen E.
奥陶纪海洋生物的主要多样化因晚奥陶世大规模灭绝（LOME）而突然终止。大约 85% 的物种在 1 m.y. 的两次脉冲中被消灭。分开。第一个脉冲发生在赫南特基底，与变冷和冈瓦南冰川作用有关。第二次脉冲发生在赫南蒂安后期，归因于变暖和缺氧。此前报道的美国内华达州、华南地区和波兰的汞 (Hg) 峰值表明危机中存在一个未知的大型火成岩省 (LIP)，但汞加载的时间导致了对 LIP 灭绝情景的不同解释，即火山活动导致变冷、变暖或两者兼而有之。我们报告了汞、钼和铀异常、生产力指标富集因子的下降以及奥陶纪-志留纪边界层型（苏格兰 Dob's Linn）的两个 LOME 脉冲之间的密切对应关系。这些支持了一种灭绝情景，即火山产生的温室气体导致卡蒂安-赫南蒂安边界周围变暖，导致先前存在的深水含氧最低区扩大、生产力崩溃和第一个洛美脉冲。赫南蒂安火山活动的重新爆发刺激了进一步的变暖和缺氧以及第二次洛美脉冲。洛美灭绝事件并不是“五大”灭绝事件中的奇特事件，其起因是变冷，而是与其他灭绝事件相似，都是由火山作用、变暖和缺氧引起的。
The Ordovician saw major diversification in marine life abruptly terminated by the Late Ordovician mass extinction (LOME). Around 85% of species were eliminated in two pulses 1 m.y. apart. The first pulse, in the basal Hirnantian, has been linked to cooling and Gond-wanan glaciation. The second pulse, later in the Hirnantian, is attributed to warming and anoxia. Previously reported mercury (Hg) spikes in Nevada (USA), South China, and Poland implicate an unknown large igneous province (LIP) in the crisis, but the timing of Hg load-ing has led to different interpretations of the LIP-extinction scenario in which volcanism causes cooling, warming, or both. We report close correspondence between Hg, Mo, and U anomalies, declines in enrichment factors of productivity proxies, and the two LOME pulses at the Ordovician-Silurian boundary stratotype (Dob's Linn, Scotland). These sup-port an extinction scenario in which volcanogenic greenhouse gases caused warming around the Katian-Hirnantian boundary that led to expansion of a preexisting deepwater oxygen minimum zone, productivity collapse, and the first LOME pulse. Renewed volcanism in the Hirnantian stimulated further warming and anoxia and the second LOME pulse. Rather than being the odd-one-out of the "Big Five" extinctions with origins in cooling, the LOME is similar to the others in being caused by volcanism, warming, and anoxia.