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. 2017 Jul 25;114(30):7929-7934.
doi: 10.1073/pnas.1705378114. Epub 2017 Jun 19.

Mercury evidence for pulsed volcanism during the end-Triassic mass extinction

Lawrence M E Percival  1 , Micha Ruhl  2 , Stephen P Hesselbo  3 , Hugh C Jenkyns  2 , Tamsin A Mather  2 , Jessica H Whiteside  4
Affiliations

Mercury evidence for pulsed volcanism during the end-Triassic mass extinction

Lawrence M E Percival et al. Proc Natl Acad Sci U S A. .

Abstract

The Central Atlantic Magmatic Province (CAMP) has long been proposed as having a causal relationship with the end-Triassic extinction event (∼201.5 Ma). In North America and northern Africa, CAMP is preserved as multiple basaltic units interbedded with uppermost Triassic to lowermost Jurassic sediments. However, it has been unclear whether this apparent pulsing was a local feature, or if pulses in the intensity of CAMP volcanism characterized the emplacement of the province as a whole. Here, six geographically widespread Triassic-Jurassic records, representing varied paleoenvironments, are analyzed for mercury (Hg) concentrations and Hg/total organic carbon (Hg/TOC) ratios. Volcanism is a major source of mercury to the modern environment. Clear increases in Hg and Hg/TOC are observed at the end-Triassic extinction horizon, confirming that a volcanically induced global Hg cycle perturbation occurred at that time. The established correlation between the extinction horizon and lowest CAMP basalts allows this sedimentary Hg excursion to be stratigraphically tied to a specific flood basalt unit, strengthening the case for volcanic Hg as the driver of sedimentary Hg/TOC spikes. Additional Hg/TOC peaks are also documented between the extinction horizon and the Triassic-Jurassic boundary (separated by ∼200 ky), supporting pulsatory intensity of CAMP volcanism across the entire province and providing direct evidence for episodic volatile release during the initial stages of CAMP emplacement. Pulsatory volcanism, and associated perturbations in the ocean-atmosphere system, likely had profound implications for the rate and magnitude of the end-Triassic mass extinction and subsequent biotic recovery.

Keywords: Central Atlantic Magmatic Province; end-Triassic extinction; mercury.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
(A) Stratigraphic correlation of the end-Triassic extinction with the Moroccan Lower Formation CAMP basalt. Argana lithology, carbon isotope, and paleomagnetic data are from ref. . Newark lithology and pCO2 data are from ref. ; paleomagnetic and astrochronological data are from ref. ; carbon isotope data are from ref. ; and trilete spore data are from ref. . St Audries Bay lithology and astrochronology are from refs. and ; biostratigraphy and carbon isotope data are from refs. and ; trilete spore data are from ref. ; and paleomagnetic data are from refs. and . Stratigraphic correlation of CAMP units between Argana, Newark, and St Audries Bay is based on refs. and . Kuhjoch biostratigraphy, lithology, and carbon isotope data are from ref. . The end-Triassic extinction horizon (marked as ETE) and Triassic–Jurassic boundary (marked as TJB) are also shown. (B) Example of Hg/TOC dataset from this study (Kuhjoch, Fig. 3) is shown to stratigraphically correlate with the lowest CAMP basalt unit that intersects the end-Triassic extinction horizon at Argana. See SI Appendix, Fig. S2 for a full stratigraphic correlation of end-Triassic records.
Fig. 2.
Fig. 2.
(A) Paleogeographic reconstruction of the end-Triassic world, with the modern continents overlain. The locations of the six studied sections are indicated (A, St Audries Bay, United Kingdom; B, Kuhjoch, Austria; C, Arroyo Malo, Argentina; D, Astartekløft, Greenland; E, Partridge Island, Canada; and F, Igounane, Morocco). The New York Canyon section in Nevada (G; note different color) studied by ref. , and CAMP are also shown (based on figure 1 from refs. and 12). (B) Summarized composite stratigraphy of Moroccan and North American CAMP basalts, following the stratigraphic relationships and ages (in million years) from refs. and . The Hickory Grove Basalt is included with the Preakness, due to their geochemical similarity. The age of the end-Triassic extinction (ETE) is also indicated.
Fig. 3.
Fig. 3.
Comparison of Hg/TOC data from St Audries Bay, Kuhjoch, Arroyo Malo, Astartekløft, and New York Canyon (35), and Hg data from Partridge Island and Iguonane (where TOC contents were below error). Letters next to locations refer to letters on the map in Fig. 2A. Carbon isotope data, biostratigraphy (ammonite first appearance), lithology, and magnetostratigraphy are also shown to allow stratigraphic correlation of the end-Triassic extinction (ETE) horizon and Triassic–Jurassic boundary (TJB). Lithological data are from St Audries Bay (10), Kuhjoch (11), Arroyo Malo (54), Astartekløft (10), Partridge Island (this study; shown in figure), Argana (14), Igouane (this study; shown in figure), and New York Canyon (35). Carbon isotope and biostratigraphic data are from St Audries Bay (10, 50), Kuhjoch (11), Arroyo Malo (ref. and this study), Astartekløft (10), Partridge Island (this study), Argana (14), and New York Canyon (35). Line M indicates the magnetostratigraphic correlation, below the extinction horizon, between St Audries Bay, Partridge Island, Argana, and Igounane. The gray shading illustrates the stratigraphic gap between line M and line ETE. Magnetostratigraphic data are from St Audries Bay (52, 53), Partridge Island (55), and Argana (14). Note, for Astartekløft, the expanded horizontal scale, and the gaps in data due to sand beds with negligible TOC. Full δ13Corg, Hg, TOC, and Hg/TOC data for each individual section are reported in SI Appendix, Table S3 and Fig. S4.
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Comment in

  • Mercury, volcanism, and mass extinctions.
    Bergquist BA. Bergquist BA. Proc Natl Acad Sci U S A. 2017 Aug 15;114(33):8675-8677. doi: 10.1073/pnas.1709070114. Epub 2017 Aug 1. Proc Natl Acad Sci U S A. 2017. PMID: 28765366 Free PMC article. No abstract available.

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