CONODONT BIOSTRATIGRAPHY AND NEW ZIRCON DATES OF THE UPPER DEVONIAN BELPRE ASHES, CHATTANOOGA SHALE, TENNESSEE, AND LOWER RHINESTREET SHALE, NEW YORK, EASTERN NORTH AMERICA

The Frasnian (Upper Devonian) Belpre Ash Suite consists of numerous discrete ash beds in the Dowelltown Member of the Chattanooga Shale. At Little War Gap, Tennessee, conodonts between the ash horizons in a 1 m thick interval include Palmatolepis punctata, P. housei, P. ljaschenkoae, Ancyrognathus barba, and Ancyrodella nodosa, which indicate placement in MN Zone 8. Ash “6” yielded a single-crystal U-Pb date of 375.40 +/- 0.13 Ma from euhedral zircon phenocrysts using the chemical abrasion (CA-TIMS) method at Boise State University. A 1 cm thick pyrite-rich ash horizon in the Rhinestreet Shale on Eighteenmile Creek – the uppermost and thickest of three ash horizons in the upper Cashequa and lower Rhinetreet in western New York - yielded a statistically identical U-Pb zircon date of 375.32 +/- 0.14 Ma. Conodonts within a 4 meter thick interval from the adjacent shale and concretions above the ash horizons include Palmatolepis ljaschenkoae, Polygnathus dubius, and A. nodosa. The conodonts and absolute dates indicate the middle Frasnian ashes in New York State are Belpre and provide a precise date for MN Zone 8. The Rhinestreet ashes underlie the Naplesites iynx epibole horizon which has been correlated with MN Zone 7.