This project focuses on the minor extinctions that restructure ecosystems on regional to continent-wide scales and commonly punctuate intervals of relative ecological stability. These geologically frequent extinction events may have a cumulative effect on the biosphere that exceeds the impact of the better-known, relatively rare global mass extinctions. Such minor extinctions are also of interest because they may be closer in scale to many of the processes of anthropogenic habitat alteration that threaten the modern biota. PIs will study two episodes of biotic turnover in the Late Ordovician trilobite faunas of eastern North America that are responses to profound environmental changes associated with the development of the Appalachian Foreland Basin during the Taconic Orogeny. They will use a comparative approach to discover features common to both events. The younger event, in the late Edenian-Maysvillian is characterized by incursions of trilobite biofacies dominated by the oleniodean, Triarthrus that may be the biotic signatures of regional paleoceanographic shifts associated with tectonically-related changes in basin configuration and/or eustasy. Other environmental changes are expressed at the older event (Turinian?Chatfieldian boundary interval) by the appearance in shallow water settings of cryptolithine trilobites, a group that typically occurs in deeper environments. Two transects into the foreland basin, Kentucky?Tennessee?Virginia and central New York?southern Ontario, will be included in the study. South-central Oklahoma, a region outside of the Appalachian foreland basin, will be used as a ?control? to help isolate faunal patterns that are unique to the basin. The environments will be reconstructed by combining data from the sedimentary rock succession with carbon isotope curves. The project includes a full treatment of the systematics, biostratigraphy and paleoecology of the trilobite faunas. The broader impact of the proposed activity lies in education and training; four graduate students and at least four undergraduates will participate in the study. PIs will also bring the broader implications of the study of extinctions to the public by developing a ?virtual exhibit? and other web-based educational resources in collaboration with the Education Department at the Oklahoma Museum of Natural History. They will consider not only extinctions in ?deep time?, but also the recent past (Quaternary extinctions) and the challenges currently facing the biosphere (such issues as global climate change, ocean acidification, and habitat destruction).
