A COMPREHENSIVE EXAMINATION OF ABSOLUTE AND RELATIVE MICROFOSSIL ABUNDANCE DURING THE LATE DEVONIAN KELLWASSER EVENTS IN THE APPALACHIAN BASIN

The cause or causes of the End-Devonian mass extinction are still poorly understood despite decades of research. One challenge is that a scarcity of macrofossils during the extinction interval itself makes it difficult to study coeval environmental changes and their potential impacts on biota. In the Appalachian Basin, the End-Devonian extinction is expressed in the Lower and Upper Kellwasser Event black shale horizons. In these strata, microfossils are present before, during, and after the extinction horizons and provide a rare glimpse into the ecological changes that took place during the extinction itself. Here, we synthesize absolute and relative fossil abundance data of acritarchs, chitinozoans, miospores, terrestrial plant matter, filaments, and arthropod cuticles from seven sites across the Appalachian Basin.

We examine trends between the Upper and Lower Kellwasser events and between proximal and distal areas of the Basin. We also interrogate the hypothesis that certain taxa of organic-walled microfossils may be “disaster taxa” that flourished during extinction events and may be related to algal blooms that could have contributed to low-oxygen conditions. In addition, preliminary results show that acanthomorphs and non-acritarch microfossils are more abundant in proximal and presumably shallower locations. This microfossil analysis, taken together with other geochemical and paleontological proxies, including Hg, total organic carbon, and microfossil morphology, provides a complex picture of ecology during the End-Devonian extinction events in the Appalachian Basin.