State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, 430074, China.
Geological Survey of Canada, Natural Resources Canada, 3303 33rd Street N.W., Calgary, Alberta, T2L 2A7, Canada.
Sci Rep. 2017 Jul 13;7(1):5304. doi: 10.1038/s41598-017-05524-5.
The second largest Phanerozoic mass extinction occurred at the Ordovician-Silurian (O-S) boundary. However, unlike the other major mass extinction events, the driver for the O-S extinction remains uncertain. The abundance of mercury (Hg) and total organic carbon (TOC) of Ordovician and early Silurian marine sediments were analyzed from four sections (Huanghuachang, Chenjiahe, Wangjiawan and Dingjiapo) in the Yichang area, South China, as a test for evidence of massive volcanism associated with the O-S event. Our results indicate the Hg concentrations generally vary in parallel with TOC, and that the Hg/TOC ratios remain low and steady state through the Early and Middle Ordovician. However, Hg concentrations and the Hg/TOC ratio increased rapidly in the Late Katian, and have a second peak during the Late Hirnantian (Late Ordovician) that was temporally coincident with two main pulses of mass extinction. Hg isotope data display little to no variation associated with the Hg spikes during the extinction intervals, indicating that the observed Hg spikes are from a volcanic source. These results suggest intense volcanism occurred during the Late Ordovician, and as in other Phanerozoic extinctions, likely played an important role in the O-S event.
华南宜昌地区黄华昌、陈家河、王家湾和丁家坡四个剖面奥陶纪-志留纪（O-S）界线附近海洋沉积物的汞（Hg）和总有机碳（TOC）含量分析，以检验与 O-S 事件相关的大规模火山活动的证据。我们的结果表明，Hg 浓度通常与 TOC 平行变化，并且在早奥陶世和中奥陶世期间 Hg/TOC 比值保持在低且稳定的状态。然而，在晚凯迪阶，Hg 浓度和 Hg/TOC 比值迅速增加，在晚赫南特期（晚奥陶世）再次达到峰值，与两次主要的大灭绝脉冲同时发生。Hg 同位素数据显示在灭绝期间与 Hg spikes 没有关联的变化，表明观察到的 Hg spikes 来自火山源。这些结果表明，晚奥陶世发生了强烈的火山活动，与其他显生宙灭绝事件一样，可能在 O-S 事件中发挥了重要作用。
