EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Mercury (Hg) anomalies and carbon isotope excursions as a stratigraphic marker for the Permian – Triassic mass extinction

Oluwaseun Edward1, André N. Paul2, Hugo Bucher3, Thierry Adatte4, Urs Schaltegger2, and Torsten Vennemann1
Oluwaseun Edward et al.
  • 1University of Lausanne, Institute of Earth Surface Dynamics, Géopolis, 1015 Lausanne, Switzerland (
  • 2Department of Earth Sciences, Université de Genève, Rue des Maraîchers 13, CH-1205 Genève
  • 3Paläontologisches Institut der Universität Zürich, Karl Schmid-Strasse 4, 8006 Zürich, Switzerland
  • 4Institute of Earth Sciences, University of Lausanne, Géopolis, 1015 Lausanne, Switzerland

Mercury concentration anomalies in sedimentary successions are widely considered as proxies for volcanism and together with negative carbon isotope (δ13C) excursions, are a common feature of many Permian-Triassic boundary (PTB) sections 1,2. On the basis of a temporal overlap of these geochemical excursions with the Permian-Triassic mass extinction (PTME) interval and PTB at the stratigraphically condensed Meishan PTB Global Stratotype Section and Point (GSSP), Hg and/or C- isotope excursions occurring stratigraphically close to the PTB are often used as chemostratigraphic markers for the extinction interval 2. However, several studies indicate that near-PTB Hg anomalies vary in their stratigraphic occurrence and expression 3; a point also noted for PTB δ13C records 4. Permian – Triassic sedimentary successions are also frequently characterized by an unconformity straddling the PTB and/or by stratigraphic condensation, questioning the robustness of PTME correlations based on these geochemical markers. This study investigates the terminal Permian to earliest Triassic Hg and δ13C record, coupled with U-Pb zircon geochronology, for two stratigraphically continuous deep-water marine sections in the Nanpanjiang Basin, South China. The results show an interval of significant Hg enrichment stratigraphically close to the PTB, which is coeval with the nadir of a negative δ13C excursion spanning the Changhsingian to Induan. U-Pb zircon geochronology of volcanic ash beds interbedded with sediments in the studied sections indicate that the onset of this Hg anomaly postdates 251.82 ± 0.060 Ma, and that the peak of the Hg anomaly (and nadir of the negative δ13C excursion) is of Griesbachian age (between 251.59 ± 0.052 Ma and 251.67 ± 0.079 Ma). The peak of the Hg anomaly and nadir of the δ13C excursion in these stratigraphically continuous marine successions post-date both the PTB (251.90 ± 0.024 Ma) and mass extinction interval (251.94 ± 0.037 Ma – 251.88 ± 0.031 Ma) as determined from the Meishan GSSP 5. Our results indicate that stratigraphical correlation of the extinction interval based on Hg anomalies and/or δ13C excursions occurring stratigraphically close to the litho- or bio-stratigraphically determined PTB should be interpreted with caution. Furthermore, this study emphasizes the importance of precise and accurate U-Pb zircon ages for stratigraphic correlation between spatially disparate localities, especially during periods of notable environmental perturbations and biotic turnover such as the Permian-Triassic transition.


1             Korte, C. & Kozur, H. W. Carbon-isotope stratigraphy across the Permian-Triassic boundary: A review. J Asian Earth Sci 39, 215-235 (2010).

2             Shen, J. et al. Evidence for a prolonged Permian-Triassic extinction interval from global marine mercury records. Nat Commun 10, 1563 (2019).

3             Sial, A. N. et al. Globally enhanced Hg deposition and Hg isotopes in sections straddling the Permian-Triassic boundary: Link to volcanism. Palaeogeogr Palaeocl 540, 109537 (2020).

4             Shen, S.-Z. et al. A sudden end-Permian mass extinction in South China. GSA Bulletin 131, 205-223 (2019).

5             Burgess, S. D., Bowring, S. & Shen, S. Z. High-precision timeline for Earth's most severe extinction. Proc Natl Acad Sci U S A 111, 3316-3321 (2014).

How to cite: Edward, O., Paul, A. N., Bucher, H., Adatte, T., Schaltegger, U., and Vennemann, T.: Mercury (Hg) anomalies and carbon isotope excursions as a stratigraphic marker for the Permian – Triassic mass extinction, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11420,, 2023.

Supplementary materials

Supplementary material file