THE DEPOSITIONAL ENVIRONMENT AND FAUNAL DIVERSITY OF THE THREE LICK BED OF THE OHIO SHALE (LATE DEVONIAN), EAST-CENTRAL KENTUCKY

This study examined the fauna contained in the type section of the Three Lick Bed of the Ohio Shale (Late Devonian), which is located in Rowan County, Kentucky, along I-64. The Three Lick Bed (a well known marker bed, especially for subsurface correlations) separates the underlying Huron Member from the overlying Cleveland Member of the Ohio Shale. The unit is 3.42 meters thick and is composed of three greenish-gray shale beds separated by two intervening black shale beds. The three greenish-gray shale units are hypothesized to have been deposited under dysaerobic conditions. The focus of this study was to examine the depositional environment and faunal diversity of the Three Lick Bed.

To date 300 kilograms of sample have been processed for macrofossils and 90 kilograms for microfossils. The samples were broken down using the kerosene technique and washed through a nested set of U. S. standard sieves, a #20 for macrofossils and a #100 for microfossils. The residue caught on the #100 sieve under went heavy liquid separation and both the heavy and the light fractions were examined for microfossils. All picking, sorting, and identification of fossils were conducted under a binocular microscope.

The results of this study support the hypothesis that the greenish-gray shale units of the Three Lick Bed were deposited in a dysaerobic environment. Evidence supporting this conclusion includes the following: 1) a low diversity macro invertebrate fauna of 18 species, 2) of the 607 specimens identified all (except Lingula) were juveniles, 3) the fauna was dominated by mollusks, 14 out of 18 species, and 4) all macro invertebrates except Lingula were preserved as pyretic internal molds. Overall, benthic foraminifera dominate the microfossil fauna in both diversity and abundance, followed by ostracodes in terms of abundance. The macrofossil fauna is dominated by cephalopods being the most diverse (with 7 species) and a low-spired gastropod being the most abundant (296/607).