2026/05/03 by Grzegorz Racki, Agnieszka Pisarzowska
Earth and Planetary Sciences · #Paleontology and Stratigraphy of Fossils #Geological and Geochemical Analysis #Geological Studies and Exploration
paper · doi:10.1016/j.palaeo.2026.113832
Time intervals near the Frasnan–Famennian (F F) and Devonian–Carboniferous (D C) boundaries are marked by stepwise extinction events (termed the Kellwasser and Hangenberg crises, respectively), accompanied by evidence of volcanic eruptions and anomalous geochemical signatures, including mercury (Hg) spikes. In this review paper, independent global datasets are interpreted in a conceptual framework to evaluate two competing hypotheses to explain the cause of these biocrises: (1) a volcanism-triggered cataclysm versus or (2) a range of single proximate killing factors, such as anoxia or cooling, with either no specified trigger, or as a response to orbital forcing or a bioevolutionary scenario. In our earlier works published in 2020, we favoured an extended (press-pulse) scenario of cataclysmic volcanism as the primary cause of these mass extinctions; however, while our hypothesis has been widely discussed, particularly with regard to supporting Hg-data, and it has been criticized as being applicable at a regional scale only. In our updated model, presented here, we discuss in detail the complex Hg signatures of the two crises. We highlight that Hg enrichment levels have been reported at least at 26 Kellwasser and 16 Hangenberg sites across three continents (including several domains of Euroamerica, Gondwana and adjacent terranes, as well as in South China) and our new dataset includes the first continental records from Greenland for both crises. Thus, the existence of a global Hg signals is confirmed. Mutually correlated volcanic proxies include Hg-based indicators, negative carbon isotope excursions, coronenes and other biomarkers, and charcoal. If the concept of a giant Siberian-East European mantle superplume is accepted, the geographic extent of Large Igneous Province (LIP) volcanism would be distinctly greater than commonly assumed. Along with evolving radiometric ages, biostratigraphic dates confirm that LIP volcanism was a significant stressor. This continuous cataclysmic factor preconditioned the global ecosystem for collapse, especially since LIPs also contribute prolonged non-eruptive degassing. Nevertheless, arc magmatism and hydrothermal activity likely played a more important role in the D C transition. We also note that Hg enrichment in the Holy Cross Mts reference succession for the Annulata and Dasberg events provides the first geochemical confirmation of the well-known Late Famennian LIP eruption phase. The origin of the final pulse(s) that led to biosphere upheaval remains unclear. In addition to orbitally forced climate changes, other factors include paroxysmal sill intrusions and non-basaltic LIP components, especially Siberian kimberlite bursts. The most speculative proposal for the F F catastrophe involves an oceanic bolide mega-impact or unusual tectonic-seismic episode. Despite the possible involvement of these other causes, a volcanic trigger for Late Devonian mass extinctions is comprehensively confirmed.