What caused Earth's largest mass extinction event? New evidence from the Permian-Triassic boundary in northeastern Utah

The discovery of a Permian-Triassic boundary section in northeastern Utah reveals a detailed record of events that led to one of the greatest mass extinctions on the planet. From 83% to 97% of the species living on the planet went extinct during this relatively short interval of geological time, which defines the major geological boundary between the Paleozoic and Mesozoic Eras. The cause and resulting sequence of events that led to this extinction have puzzled geologists for years. A new stratigraphic section in Utah provides details enabling the reconstruction of the events that led to this mass extinction. Geochemical analysis of the section demonstrates a significant drop in carbonate and total organic carbon, and a delayed occurrence of pyrite framboids. Carbon isotope ratios (δ13C) show a negative excursion in carbonate with ratios dropping from 2.585‰ to -3.627‰. Elevated mercury is present at the boundary with a 4-fold increase from background levels. The boundary layer shows elevated zinc, lead, strontium, and nickel, but not at high enough levels to indicate a volcanic ash source. There is no evidence in concentrations of siderophile and chalcophile elements for an extraterrestrial impact. The stratigraphic section in Utah supports the theory of a massive release of carbon dioxide, resulting in the acidification of the oceans. High levels of mercury, as well as elevated levels of zinc and lead, implicate a coal source triggered by the contemporary Siberian Traps sill complex. The delay of enriched sulfur and barium content in the stratigraphic record indicates an anoxic ocean and upwelling of methane hydrates from depth. Further study of this stratigraphic section will aid our understanding of the global impact these catastrophic events had on life and hopefully prevent it from happening again.

犹他州东北部发现的二叠纪-三叠纪边界层揭示了导致地球上最大规模灭绝事件之一的一系列事件的详细记录。在此相对短暂的地质时期内，地球上83%至97%的物种灭绝，这定义了古生代和中生代之间的主要地质界限。导致此次灭绝的原因及其引发的系列事件多年来一直困扰着地质学家。犹他州新发现的层序剖面提供了重建导致此次大规模灭绝事件的详细信息的依据。对该剖面的地球化学分析显示，碳酸盐和总有机碳含量显著下降，以及黄铁矿球粒的延迟出现。碳同位素比率（δ13C）显示碳酸盐中的负偏离，比率从2.585‰降至-3.627‰。边界处汞含量升高，背景水平增加4倍。边界层显示出锌、铅、锶和镍含量升高，但不足以表明火山灰来源。在亲铁元素和亲硫元素浓度中没有发现外星撞击的证据。犹他州的层序剖面支持了大规模二氧化碳释放的理论，导致海洋酸化。汞含量以及锌和铅含量升高暗示了由同时期的西伯利亚 traps 熔岩穹窿触发的煤源。层序记录中富含硫和钡含量的延迟表明缺氧海洋和深海甲烷水合物上涌。进一步研究这一层序剖面将有助于我们理解这些灾难性事件对生命的全球影响，并有望防止其再次发生。