ECOLOGICAL GRADIENT ANALYSIS OF BRACHIOPODS THROUGH THE FRASNIAN-FAMENNIAN MASS EXTINCTION INTERVAL (LATE DEVONIAN) OF TIOGA, PENNSYLVANIA

The Frasnian-Famennian mass extinction event of the Late Devonian occurred in two pulses, the Lower and Upper Kellwasser events. Upper Devonian rocks of Tioga in north-central Pennsylvania preserve shallow marine facies of the Appalachian Foreland Basin spanning the Frasnian-Fammenian boundary interval. Prior investigations of the paleontology of this region have focused on the fates of rhynchonelliform brachiopods across the Lower Kellwasser event; in this study, we expand our database to post-Upper Kellwasser strata and analyze changes in the fossil record through the entirety of the extinction interval. Using fossil abundance counts from bulk samples, we compare faunal assemblages before and after both extinction events, noting both faunal turnover as well as changes in relative abundances of taxa. Using non-metric multidimensional scaling (nMDS), we construct paleoecological gradients before the Lower Kellwasser event, between the two events, and after the Upper Kellwasser event. These analyses show how brachiopod species responded to paleoenvironmental changes through this stratigraphic interval, including mass extinction triggers and changes in water depth. We also compare the nMDS results to a previously conducted facies analysis (Beard et al. 2017, Palaeogeography, Palaeoclimatology, Palaeoecology, v. 478, p. 67-79). By examining changes within shallow marine ecosystems through past mass extinction events, we may better understand potential future effects of environmental and ecological perturbations associated with climate change.