Paper No. 10-12
Presentation Time: 11:05 AM
PRELIMINARY CONODONT BIODIVERSITY DATA FROM THE GIVETIAN-FRASNIAN “FRASNES EVENT” INTERVAL IN THE NORTHERN ANTELOPE RANGE NEVADA, USA
The Devonian includes large-scale, short-lived changes reflected in the rock record as coeval black shales, carbon isotope events, and extinction events. Middle-Upper Devonian strata exposed in the northern Antelope Range in Nevada include the Denay Limestone, which contains the “Frasnes Event”, a second-order global mass extinction and black shale episode occurring around the Givetian-Frasnian boundary. It is also stratigraphically close to the falsiovalis positive carbon isotope excursion. Studies on the extinction event have mainly focused on macrofossil groups and the possible effects on conodonts are understudied. More data on conodont species ranges relative to the timing of the Frasnes event and falsiovalis excursion are needed from diverse global sections in order to assess any possible relationship between the Frasnes and biodiversity changes. Nine large (5 kg) conodont samples through the approximately 20-meter-thick event interval within the Denay Limestone were taken for processing, specimen identification, and assignment to the global conodont zonation. Richness and evenness were evaluated for each sample and compared between samples, using rarefaction curves to standardize sample size. Species ranges were plotted to identify possible turnover or extinction events in the section. Future work will incorporate results from carbonate carbon isotope samples that were taken from the same section at the time of the conodont sampling to compare conodont biodiversity dynamics to the carbon isotope signal.