Abstract: An Integrated, Multidisciplinary Stratigraphic Research Project on the Late Ordovician Mass Extinction

FINNEY, STANLEY C.

The Late Ordovician mass extinction reduced species diversity more than 50% and eliminated 20% of marine families. It has been linked to Gondwanan ice sheets, global cooling and the restriction of climatic belts, a prominent sea level fall and subsequent rise, and changes in oceanic upwelling, nutrient abundance, and water chemistry. The Late Ordovician extinction has not generated the same widespread publicity as the K/T and Permian-Triassic events, yet it has much to offer as an example of a climatically driven event. Study of the extinction has been hindered by the lack of stratigraphic sections spanning the extinction interval; most sections are marked by a major hiatus. Those few that are not are in facies with limited fossil control and are not amenable to sequence stratigraphic, chemostratigraphic and magnetostratigraphic analyses.

Recently discovered sections in central Nevada, however, have the potential to overcome these problems. They provide a unique opportunity to precisely correlate: 1 ) the biostratigraphic distributions of graptolites, conodonts, organic-walled microfossils, and shelly fossils, 2) carbon-isotope stratigraphy, 3) magnetostratigraphy, and 4) the sedimentological record of glacioeustasy. The sections have been studied and sampled by a multidisciplinary team of scientists and students, whose goal is to determine with high resolution the temporal interrelationships of biotic, oceanic, and atmospheric events as a means of understanding the mechanistic linkages between them. The integrated, multidisciplinary approach is the key to successfully analyzing and integrating the various data sets.

Search and Discovery Article #90945©1997 AAPG Pacific Section Meeting, Bakersfield, California