Upper Devonian mercury record from North America and its implications for the Frasnian–Famennian mass extinction

The Frasnian–Famennian biotic crisis (~372 Ma) was one of the “big five” mass extinction events in the Phanerozoic. This event was associated with dramatic climatic and oceanographic perturbations, including oceanic anoxia, global cooling, sea-level fluctuations. Large-scale volcanic activity is one of several possible triggers that have been suggested as the ultimate cause of this crisis, based on Hg enrichment data from widespread sections. However, there are also sections that do not show a Hg enrichment across the Frasnian–Famennian boundary. To further investigate the hypothesis of a volcanic trigger for the Frasnian–Famennian mass extinction event, mercury (Hg) analyses were performed on six North American records (five from the Appalachian Basin and one in the Illinois Basin) that include the Frasnian–Famennian boundary. There is no uniformly observed Hg enrichment at or below the Frasnian–Famennian boundary across the six sites. A potentially volcanically driven Hg anomaly is found in the Illinois Basin; however, the Hg enrichment occurs stratigraphically above the Frasnian–Famennian boundary. Mercury records from the studied sites question the timing of the volcanism that may be responsible for the mass extinction event. Further studies are needed to fully understand the geographic distribution and eruption history of the large igneous provinces, as well as the link between Hg and volcanism during the Frasnian–Famennian interval.