ACULEATUS ZONE AGE OF THREE LICK BED TYPE LOCALITY, OHIO SHALE, UPPER DEVONIAN, EASTERN KENTUCKY

The Three Lick Bed separates the Huron Shale Member of the Ohio Shale from the overlying Cleveland Shale Member, which are part of the Upper Devonian fine-grained marine siliciclastic strata in the Appalachian Basin. At the type locality in Rowan County, Kentucky, the Three Lick Bed consists of three distinct greenish-gray shales in a 3.5 m interval within the upper third of the 55 m thick black shale dominated Ohio Shale; the interval is relatively easy to identify on gamma-ray logs and in the field. The Three Lick Bed is interpreted as the distal edge of the Chagrin Shale, representing a dysoxic substrate in contrast to the typically anoxic substrate of the black Huron and Cleveland shales. Conodonts and a mollusk-dominated dysaerobic fauna preserved as pyritized internal molds were recovered from all three beds. The lower bed yielded Bisptahodus stabilis, Branmehla inornata, Palmatolepis expansa, Pa. grossi, Pa. gracilis, Pa. schindewolfi, and Polygnathus perplexus. The middle bed yielded Bi. anteposicornis, Bi. stabilis, Br. disparalis, and Pa. aff. Pa. rugosa, Pa. sigmoidalis, Po. perplexus, and Po. cf. Po. subirregularis. The upper bed yielded Bi. stabilis, Mehlina sp., Pa. gracilis, and Pa. sigmoidalis. In an earlier study the Three Lick Bed was considered no higher than the expansa Zone (= former Lower expansa Zone) based on the occurrence of Pa. maxima in the black shale between the middle and upper green-gray shale beds and the interpretation of its range at that time. The recovery of Bi. anteposicornis, which first occurs in the aculeatus Zone (= former lower portion of Middle expansa Zone, from the middle Three Lick Bed and the range of Pa. maxima into the aculeatus Zone indicates the middle and upper Three Lick Beds are within the aculeatus Zone and possibly restricted to the lower portion of the zone due to the narrow overlap in the ranges of these two taxa.