Recognition of Four Distinct Limestone Beds in the Lead Creek Limestone Member of the Tradewater Formation (Atokan, Middle Pennsylvanian) in Western Kentucky and Southwestern Indiana

Early workers recognized that the Lead Creek Limestone in Hancock County, Kentucky, includes up to four beds of limestone separated by shale and sandstone, but developed no criteria for their recognition. Later, two limestone beds were named from a southern Indiana exposure, where the upper Ferdinand Bed contains chert and the lower Fulda Bed lacks chert. This fostered the misconception that the Lead Creek Limestone contains only two limestone beds. Subsequent geologic mapping readily recognized the cherty Ferdinand Bed and assumed that the underlying limestone was Fulda. Our investigation of Lead Creek outcrops and deep drill cores in Indiana and Kentucky showed that the second bed down is limestone, and the third bed down is largely dolomitic. Each of these three limestone beds yielded similar conodont faunas dominated by Idiognathodus sp. Q, accompanied by lesser numbers of Idiognathoides and Neognathodus. The KGS Gil-23 core from Butler County, Kentucky, contains three limestone beds, which we identified elsewhere based on lithologic features or by the conodont faunas above. The core also has a lower dark calcareous shale bed that yielded the Fulda conodont fauna, which contains the only appearance of Declinognathodus accompanying Idiognathoides. We correlate this lower bed with the Fulda Limestone Bed. Therefore, the names of the upper “Ferdinand” and lowermost “Fulda” beds are retained and new formal names are proposed for the two middle limestone beds. In descending order, the Lead Creek Limestone Member comprises the Ferdinand, Hilldale, Little Sandy, and Fulda limestone beds.