256-6 Stratigraphic Controls on the Late Serpukhovian (Mississippian, Carboniferous) Mass Extinction Event in the Global Type Section

Session: Life and Environments Through Time and Space: Multi-Record Approaches to Stratigraphic Paleobiology, Part I

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Abstract:

Clusters of fossil last occurrences are used to delineate extinction horizons. These clusters, however, are controlled by the structure of the stratigraphic record, such that clusters are typically found below stratigraphic horizons that mark major changes in facies (relative water depth), such as flooding surfaces and subaerial unconformities. As such, the structure of the stratigraphic record could potentially influence how extinction events are interpreted from field observations. The late Serpukhovian (late Mississippian) mass extinction event is the seventh largest of the Phanerozoic with 26-28% generic extinction and occurred during the onset of the Late Paleozoic Ice Age during a time of high-frequency and high-amplitude glacioeustasy. Field-based studies from the North America craton demonstrate that uppermost Serpukhovian marine invertebrates track their preferred habitats, with overall richness patterns remaining stable across the Serpukhovian-Bashkirian boundary (uppermost Mississippian–lowermost Pennsylvanian). These studies reveal evidence against an extinction event during the upper Serpukhovian, with observed taxonomic turnover principally attributed to extirpation and facies preservation, but not true extinction. Here, we provide further insight into the late Serpukhovian extinction event by documenting brachiopod assemblages across the mid-Carboniferous global boundary stratotype section and point (GSSP) at Arrow Canyon in southern Nevada. A combination of facies analysis and multivariate quantitative methods from field observations and previously collected, unpublished material was used to document taxonomic composition between the upper Serpukhovian Indian Springs Formation and the uppermost Serpukhovian to lowermost Bashkirian section of the Bird Spring Formation. Results show an overall increase in generic richness throughout the uppermost Serpukhovian and across the boundary into the lowermost Bashkirian, where richness peaks. Additionally, 19% of Serpukhovian genera are not present in the Bashkirian of Arrow Canyon. However, global stratigraphic ranges reveal that all but two Serpukhovian taxa persisted into the Bashkirian, with some taxa even occurring higher in the unstudied section at Arrow Canyon. Multivariate analysis reveals similar taxonomic composition between Serpukhovian and Bashkirian assemblages, with a notable gradient driven by differences in lithology and water depth. These results further suggest a lack of a late Serpukhovian extinction event in North America and highlight how working with the structure of the stratigraphic record can untangle biological signals from stratigraphic patterns.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8513

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