BIOSTRATIGRAPHY, LITHOSTRATIGRAPHY, AND SEQUENCE STRATIGRAPHY ACROSS THE FRASNIAN/FAMENNIAN EXTINCTION IN THE SOUTH-CENTRAL APPALACHIAN BASIN

Integration of high resolution data sets of biostratigraphy, lithostrartigraqphy, and sequence stratigraphic analyses offers a detailed look at the Late Devonian biotic events. The data set is based on the compilation of biostratigraphic ranges defined by 30,000 macrofossils and detailed measured sections from eight different geographic locations from the Upper Devonian of Virginia. The high resolution data offers a detailed examination of the geologic record surrounding the Frasnian/Famennian extinction. Two separate pulses cause approximately 50% of the brachiopods go extinct while bivalves do not show a decline in number of species. Correlations of this data and the Johnson, Klapper, and Sandberg sea-level curve indicates a realtively high sea-level just before the extinction and a significant drop in sea-level at or near the extinction. Ideally, conodonts and brachiopods would be found together in the same rock for absolute correlations. This is with out a doubt not the case in Virginia. Further correlations were made with sequence stratigraphy in an attempt to correlate 16 local brachiopod biozones with the established conodont biozonation. If the correlation proves to be relatively correct than the 16 brachiopod zones could be used as time indicators in near shore clastic environments and other strata that do not yield many or any conodonts. There is still a great deal of information to glean from the near shore sediments of Appalachian basin if there was a framework that did not rely on conodonts. This new tool will be useful in determining accurate placement of the Frasnian/Famennian boundary in locations that do not have key indicator species or conodonts. Continued work along the Appalachians towards Pennsylvania will hopefully yield more high resolution data that can be used to better understand the Late Devonian events.