ORGANIC-WALLED MICROFOSSIL ASSEMBLAGE VARIATION THROUGH THE LATE DEVONIAN KELLWASSER EVENTS IN NEW YORK STATE

The Kellwasser Events are globally expressed as two black shale horizons associated with the Late Devonian Extinction and the Frasnian/Famennian transition and have been interpreted as a signal of widespread marine anoxia correlated with the extinction interval. In Western New York, the Kellwasser horizons were deposited in the epeiric sea of the eastward-shallowing Appalachian Basin. While larger body fossils are mainly absent within the Kellwasser horizons, organic-walled microfossils, classified as acritarchs, are abundant and provide a nearly continuous record throughout the events.

Here we assess microfossil morphology, diversity, and abundance through the Kellwasser Events at two main localities in New York State. In all localities, microfossil diversity is very low relative to surveys of Devonian palynoflora, a trend indicative of ecological stress. The Upper Kellwasser horizon assemblages included only simple smooth-walled leiosphere fossils, and there was were no significant differences between assemblage morphologies and abundance trends between the Kellwasser horizon and the overlying Dunkirk formation, indicating that the environmental conditions of the Upper Kellwasser Event persisted after the event.

In contrast, we find that the microfossil assemblages of the Lower Kellwasser Event show significant variation. This indicates that the Lower Kellwasser Event was more biologically significant than the Upper Kellwasser Event, adding support to similar findings in the Appalachian Basin, yet conflicting with the biological pattern in Europe. Additionally, the palynological record may show evidence of algal bloom events, and associated eutrophication, co-occurring at the sea level maximum and the peak in preserved organic carbon. These findings contribute to a better understanding of environmental conditions during their Kellwasser Events and their possible role in the Late Devonian Extinction.