Volcanism of the Central Atlantic magmatic province as the trigger of environmental and biotic changes around the Triassic-Jurassic boundary

Abstract

In the last decade, major advances have been made in our understanding of the end-Triassic mass extinction, related environmental changes, and volcanism of the Central Atlantic magmatic province. Studies of various fossil groups and synoptic analyses of global diversity document the extinction and subsequent recovery. The concomitant environmental changes are manifested in a series of carbon isotope excursions (CIE), suggesting perturbations in the global carbon cycle. Besides the earlier-recognized initial and main negative anomalies, a more complex picture is emerging with other CIEs, both negative and positive, prior to and following the Triassic-Jurassic boundary. The source of isotopically light carbon remains debated (methane from hydrate dissociation vs. thermogenic methane), but either process is capable of amplifying an initial warming, resulting in runaway greenhouse conditions. Excess CO2 entering the ocean causes acidifi cation, an effective killing mechanism for heavily calcifi ed marine biota that appears implicated in the reef crisis. The spatial and temporal extent of Central Atlantic magmatic province volcanism is established through a growing data set of radiometric ages. Since the Central Atlantic magmatic province is one of the largest Phanerozoic large igneous provinces, volcanic CO2-driven warming is plausible as a key factor in the chain of Triassic-Jurassic boundary events. Greenhouse warming may have been punctuated by short-term cooling episodes due to H2S emission and production of sulfate aerosols, a process more diffi cult to trace in the stratigraphic record. Taken together, recently generated data signifi cantly increase the support for Central Atlantic magmatic province volcanism as a viable trigger for the environmental and biotic changes around the Triassic-Jurassic boundary.