Two LIPs and two Earth system crises: the impact of the North Atlantic Igneous Province and the Siberian Traps on the Earth-surface carbon cycle

The links between the Siberian Traps and the end- Permian mass extinction, and between the North Atlantic Igneous Province (NA IP) and the Palaeocene-Eocene Thermal Maximum (PETM), demonstrate a critical role for large-igneous provinces (LIPs) in the disruption of the Earth-system carbon cycle (ESCC). High-precision age dates for both volcanic provinces and the associate d environmental crises show that in both cases, the crisis was contemporaneous with the volcanism. The NAIP comprises two phases: the earlier Phase 1 (~61 Ma), and the m uch more voluminous Phase 2, ~56 Ma, linked to the opening of the NE Atlantic. The l atter triggered the PETM, the largest Cenozoic hyperthermal. The Siberian Traps are sign ificantly more voluminous than the NAIP, and triggered the end-Permian mass extinction . The masses of volcanic CO 2 emitted from these provinces may have been much gre ater than previously suggested, because substantial gas may come from intrusive bod ies deep within the crust (cryptic degassing: Armstrong McKay et al., 2014). Precurso ry warming due to the accumulation of volcanic CO 2 in the atmosphere likely triggered the release of low- δ 13 C methane hydrate, although the masses of methane hyd rate alone may have been insufficient to account for the observed temperatur e rises; the organic C was likely strongly supplemented by magmatically-derived carbo n and thermogenic carbon released during emplacement of sills and dykes into C-rich sedimentary units. More data are required on the volcanic flux rates in ord er to refine the cause-effect relationships between LIPs and the ESCC.