Extinction and Recovery of Crinoids Resulting from Climatic Change during the Ordovician-Silurian Biotic Crisis

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Crinoids (Phylum Echinodermata) were among the most important marine organisms throughout the Paleozoic (ca 570 to 265 million years ago). They were dominant in maintaining the ecological structure Paleozoic communities, in diversity and abundance among echinoderms, and in importance as sediment contributors that ultimately led to the limestones of today. However, end-Ordovician global environmental change resulted in a mass extinction of crinoids and, ultimately, a macroevolutionary reorganization of crinoids as they diversified during the Early Silurian. End-Ordovician environmental change was caused by global cooling and sea level lowering resulting from a continental glaciation on the southern paleocontinents. A thorough understanding of the end-Ordovician biotic crisis will provide an important example of the consequences of global environmental change in deep time against which to compare global environmental changes that have occurred in the most recent past and for predicting future oceanic impacts of global environmental change. The objectives of this proposal are the following. 1) Field collection and study of crinoids in strata immediately surrounding the Ordovician-Silurian boundary, i.e. the Ellis Bay and Becscie formations. 2) Collection of samples for isotopic analysis will be coordinated with work by our Canadian colleagues in order to develop as thorough an understanding as possible of these stratigraphic sections. The plan is to sample the Ashgillian Vaureal Formation, for which isotopes are not known, and to take samples in formations that span the O-S boundary in unsampled sections in the eastern part of the island. 3) Within the time available, integrate the two data sets to further develop an understanding of whether the Anticosti Island Ordovician-Silurian succession is complete or whether there are paraconformities present that would affect the objectives of the study being proposed. and 4) provide a research learning experience for undergraduate and graduate students through field studies, laboratory research, and preparation of theses (undergraduate and graduate).