Rapid enhancement of chemical weathering recorded by extremely light seawater lithium isotopes at the Permian-Triassic boundary

Abstract

Lithium (Li) isotope analyses of sedimentary rocks from the Meishan section in South China reveal extremely light seawater Li isotopic signatures at the Permian-Triassic boundary (PTB), which coincide with the most severe mass extinction in the history of animal life. Using a dynamic seawater lithium box model, we show that the light seawater Li isotopic signatures can be best explained by a significant influx of riverine [Li] with light δ⁷Li to the ocean realm. The seawater Li isotope excursion started ≥300 Ky before and persisted up to the main extinction event, which is consistent with the eruption time of the Siberian Traps. The eruption of the Siberian Traps exposed an enormous amount of fresh basalt and triggered CO₂ release, rapid global warming, and acid rains, which in turn led to a rapid enhancement of continental weathering. The enhanced continental weathering delivered excessive nutrients to the oceans that could lead to marine eutrophication, anoxia, acidification, and ecological perturbation, ultimately resulting in the end-Permian mass extinction.

Keywords: Li isotopes; Meishan section; Permian–Triassic boundary; continental weathering; end-Permian mass extinction.