Two episodes of Gzhelian (latest Carboniferous) volcanism immediately predate Asselian (early Permian) cooling and glaciation

The Skagerrak-Centered large igneous province (SCLIP) was active 299 million years ago when Earth's climate transitioned into an interval of intensified glaciation. A link between the SCLIP and global climate change has been hypothesized but there is little direct evidence of concurrent volcanism and climate change in coeval sedimentary layers from the late Carboniferous to the early Permian. We combined carbon isotopes, mercury contents and isotopes, and elemental geochemistry of the Taiyuan Formation in the Hedong Coalfield, North China to identify two episodes of volcanism during the early and late Gzhelian (latest Carboniferous). Both episodes are marked by Hg enrichments, positive Δ 199 Hg excursions and negative δ 13 C org excursions; only late Gzhelian volcanism was associated with reduced rates of continental weathering and was followed by global cooling. We hypothesize that the late Gzhelian volcanic episode had a greater environmental impact than that in the early Gzhelian because late Gzhelian volcanism was likely more intense and of longer duration. The SCLIP may have contributed to global cooling via the release of sulfate aerosols that results in atmospheric cooling and/or from ocean fertilization and increased removal of organic carbon via the biological pump. • Hg enrichment and isotopes reveal late Carboniferous volcanic pulses in North China. • Weaker early Ghzelian and stronger late Ghzelian volcanic pulses. • Negative δ 13 C org excursions coincide with each volcanic pulse. • Asselian (early Permian) post-volcanism cooling and continental weathering decrease. • Different environmental responses to two pulses of Gzhelian volcanism.