DESCRIPTION OF A LATE MISSISSIPPIAN (CHESTERIAN) VERTEBRATE BEARING LIMESTONE UNIT WITHIN THE LEITCHFIELD FORMATION

During a recent small-scale excavation a geologic unit, within the Mississippian Leitchfield Formation (Chesterian), was exposed along State Route 259 in Grayson County, Kentucky, south of the city of Leitchfield. The lithology of the unit is composed of shales, mudstones, sandstones, and limestones. Within this unit, there is a fossiliferous limestone which upon weathering turns yellowish in color due to the oxidation of its iron content. The unweathered unit is light to medium grey in color. The layer is 1.5 centimeters thick at its thinnest, and 28 centimeters in thickness at its maximum. In addition, a 6 centimeter thick shale layer sits atop the thickest part of the limestone layer and is also fossiliferous in content. These two units, within the Leitchfield formation, contain both terrestrial and marine vertebrate remains, including chondrichthyan teeth, denticles, and scales; osteichthyan jaws, teeth, scales and boney elements; sarcopterygian remains including teeth and bones, and amphibian remains consisting of boney elements. Furthermore, these two units appear to be a vertebrate bone-bed layer. Currently, analysis of the lithology, depositional environment, and taxonomic identification and description of the vertebrate material contained within the unit is underway. Additional research will help define the lateral extent of this bone-bed layer at other Leitchfield Formation exposures in Grayson County.