A PREVIOUSLY UNDESCRIBED MIDDLE DEVONIAN BONE BED WITHIN THE BOYLE FORMATION NEAR MINA, KENTUCKY

A paleontologically important, well preserved macro- and micro-vertebrate fauna was obtained from a previously undescribed site within the Middle Devonian (Givetian) Boyle Formation.  The exposure consists of a series of road-cuts located on the west side of KY Rt. 89, approximately two miles south of the town of Mina. The outcrop exposes approximately 6 meters of the Boyle Formation, which is unconformably underlain by Middle Silurian Crab Orchard Formation, and overlain by 3 meters of the Late Devonian New Albany Shale.

The previously undescribed bone rich bed occurs within a distinct, 10 cm layer that spans portions of the exposure. The lithology of the layer consists of an olive-gray to brownish-gray, fine to medium-crystalline dolomitic limestone. Copious well preserved macro- and micro-vertebrate remains and phosphatic nodules are scattered primarily on the upper surface and within the upper two -to- three centimeters of the layer.

Macro-vertebrate remains include disarticulated arthrodire plates and isolated skeletal elements, as well as sarcopterygian tooth plates and teeth. Micro-vertebrate material consists of abundant conodont elements, acanthodian and paleonisciform actinopterygians scales, chondrichthyan dermal denticles and teeth. Chondrichthyans are represented by the cladoselachids Stethacanthus and Symmorium, by the phoebodontids Phoebodus and Thrinacodus?, by members of the genus Protacrodus, as well as several undescribed species.

Stratigraphically, the Mina bone bed layer occurs within the Kiddville Member of the Boyle Formation (Conkin et al., 1973), yet does not appear to correspond to any bone beds described therein. Surprisingly, the vertebrate fauna appears to be similar to Middle- to- Late Devonian faunas described within the Ohio Shales and the uppermost Delaware Limestone of Central and Northeastern Ohio (Wells 1944). Given this discrepancy, future work will focus on careful lithostratigraphic, sequence stratigraphic, and biostratigraphic analysis, as well as faunal correlation with other Late Devonian faunas in the Midwest.