Evidence for shallow-water ‘Upper Kellwasser’ anoxia in the Frasnian–Famennian reefs of Alberta, Canada

The Frasnian–Famennian extinction witnessed the global devastation of both level-bottom and reef communities in low latitudes. Marine extinctions in offshore level-bottom communities are associated with two widespread, transgressive, anoxic ‘Kellwasser Events’ that support an anoxia–extinction link. Typical Kellwasser facies of bituminous limestones and shales are not obviously recorded in shallow-water settings, and thus, it is unclear whether...