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. 2017 Jul 13;7(1):5304.
doi: 10.1038/s41598-017-05524-5.

Mercury spikes suggest volcanic driver of the Ordovician-Silurian mass extinction

Qing Gong  1 , Xiangdong Wang  1 , Laishi Zhao  2 , Stephen E Grasby  3 , Zhong-Qiang Chen  1   4 , Lei Zhang  1 , Yang Li  1 , Ling Cao  1 , Zhihong Li  5
Affiliations

Mercury spikes suggest volcanic driver of the Ordovician-Silurian mass extinction

Qing Gong et al. Sci Rep. .

Abstract

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.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Figure 1
Figure 1
Palaeogeographic map of Yangtze block area during the Late Ordovician. Modified from Zhou et al.. The study sections are at Yichang, South China.
Figure 2
Figure 2
Geochemical plots of trends in Hg, TOC (total organic carbon) and Hg/TOC for Yichang sections through Ordovician and Lower Silurian. Yichang sections include Huanghuachang, Chenjiahe and Wangjiawan. Abbreviation: S = Series, St = Stage, Fm. = Formation, Wf. = Wufeng, Kyc. = Kuanyinchiao, Lmc = Lungmachi, Hrn. = Hirnantian, Rh. = Rhuddanian.
Figure 3
Figure 3
Geochemical plots for Wangjiawan (A) and Dingjiapo (B) sections across the Ordovician-Silurian boundary. Plots show variation of δ13Corg for Wangjiawan and Hg, TOC, Hg/TOC, Hg/Mo, δ202Hg and Δ199Hg for Wangjiawan and Dingjiapo. Graptolitic zone is from Chen et al. and δ13Corg data are from Yan et al.. Abbreviation: Fm. = Formation, Kyc. = Kuanyinchiao.
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