PALEOECOLOGY AND DIVERSITY OF BRACHIOPODS THROUGH THE UPPER KELLWASSER EXTINCTION EVENT (LATE DEVONIAN) AT 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-Famennian boundary interval, including both extinction pulses. We present an updated facies analysis of two outcrops in this area, one crossing the Pipe Creek Formation (the temporal equivalent of the Lower Kellwasser event) and including the latest Frasnian, and the other encompassing the early Famennian, lying just above the F-F boundary. Using fossil abundance counts from bulk samples, we analyze changes in faunal assemblages of rhynchonelliform brachiopods through the extinction interval, noting both faunal turnover and changes in relative abundances of taxa. Using non-metric multidimensional scaling (nMDS), we reconstruct paleoecological gradients before and after the Upper Kellwasser event. Using these results, we examine changes in sample-level species richness (alpha diversity) along the onshore-offshore paleoenvironmental gradient as well as through time (across the extinction event). These analyses help reveal how the brachiopod faunal assemblage structure was affected by environmental perturbations in the Late Devonian in this region. Hopefully, studying changes within shallow-marine ecosystems during past mass extinction events may help us to better understand potential effects of anthropogenic climate change on modern environments and ecosystems.