PALEOENVIRONMENTAL SELECTIVITY OF THE LOWER KELLWASSER MASS EXTINCTION EVENT (LATE DEVONIAN) IN NEW YORK AND PENNSYLVANIA

Within the last 500 million years, five major mass extinction events have tested the adaptability and survivability of organisms. Assessing the selectivity of such events—which types of organisms survived versus died out—can help pinpoint the environmental changes that drove extinction including ocean anoxia, ocean acidification, and climate change. The aim here was to test the paleoenvironmental selectivity from the Lower Kellwasser event, the first pulse of the Frasnian-Famennian mass extinction in the Late Devonian. A thick package of siliclastic sediments was deposited in the Appalachian Foreland Basin in New York and Pennsylvania during the Late Devonian, representing a shallowing paleoenvironmental gradient from west to east. Previous studies have shown that brachiopod species composition varies significantly along this gradient, the Lower and Upper Kellwasser events can be traced along the gradient thanks to recent stratigraphic revisions. More specifically, the Wiscoy Formation was targeted for this study as it immediately predates the first extinction pulse and brachiopod environmental preferences can therefore be determined prior to Lower Kellwasser disturbances. Bulk samples were collected from numerous localities along this water-depth gradient. We have identified 8,485 brachiopod fossils from 22 genera and over 27 species. Non-metric multidimensional scaling was used to tease apart variation among species in water depth preference. Preliminary analysis shows a clear separation of shallow and deep-water taxa along one axis. Ambocoelia gregaria, which we believe to be an opportunistic and rapidly blooming species separates from the other taxa along a second axis. We examined whether species known to disappear after the first extinction pulse tend to live preferentially in shallow or deep water, which can help constrain possible kill mechanisms associated with the Kellwasser events.