Stratigraphic controls on the Serpukhovian (Upper Mississippian, Carboniferous) mass extinction at the mid-Carboniferous global boundary type locality

Global diversity patterns delineate the Serpukhovian (Upper Mississippian, Carboniferous) mass extinction as the seventh-largest of the Phanerozoic, with 26–28% of genera extinct. Studies of Serpukhovian marine assemblages from North America, however, exhibit stable diversity patterns across the Serpukhovian–Bashkirian boundary. These studies provide evidence against an extinction event during the Serpukhovian, with observed taxonomic turnover attributable to extirpation and facies preservation rather than true extinction. Here, we provide further insight into the Serpukhovian extinction at the mid-Carboniferous Global Boundary Stratotype Section and Point (GSSP) in Arrow Canyon, southern Nevada, USA. Assessing brachiopod assemblages within their facies context, we test for evidence of the Serpukhovian mass extinction. Results reveal that 39% of Serpukhovian genera are absent from the Bashkirian at Arrow Canyon. However, global stratigraphic ranges reveal that all but two Serpukhovian taxa persisted into the Bashkirian. Multivariate analysis reveals similar taxonomic composition between the Serpukhovian and Bashkirian assemblages, with a notable lithological gradient driving local variation between geologic units. These results further suggest the absence of a late Serpukhovian extinction event in North America and highlight how working with the structure of the stratigraphic record can separate biological signals from stratigraphic patterns.