Global impact of the Siberian Traps
Earth’s most severe mass extinction occurred 252 million years ago and is believed to have been caused by volcanic eruptions from the Siberian Traps in the northern hemisphere. Among the large amounts of gas and material released during these eruptions was the chemical element Mercury (Hg), which was transported through the atmosphere and deposited in sedimentary basins. While this Hg signature is well studied in stratigraphic sections and particularly marine sections from the northern hemisphere and equatorial regions, data from southern terrestrial sites are lacking.
Jun Shen at the China University of Geosciences and colleagues analyse Hg concentration and isotope data in stratigraphic sections taken from two terrestrial sites in the southern hemisphere: the Karoo Basin in South Africa and the Sydney Basin in Australia – the farthest terrestrial sites from the Siberian Traps to have been studied for volcanic Hg content. The team observe spikes in the Hg concentration profiles of these sections around the Permian-Triassic boundary. Additionally, analysis of the mass-independent fractionation values of Mercury’s stable isotope Hg-199 implies that the Hg contained in the sediments was atmospherically sourced following long-distance transportation and is, therefore, likely volcanic in origin.
The Hg profiles that were derived from the Karoo Basin sections support growing evidence that the end-Permian mass extinction occurred in phases over 10,000 to 100,000 years. The results also enable a more accurate placement of the extinction interval in the Karoo Basin, which has long been a topic of discussion.
In addition to providing greater insight into the global effects of the Siberian eruptions, this study secures Mercury as a reliable chemical tracker of past volcanic activity in both marine and terrestrial successions.
Nat. Comm. 14, 6 (2023); doi.org/10.1038/s41467-022-35272-8