Abstract

The Kinkaid Formation is the uppermost formation in the standard section of the Chester Series for the Mississippian System in North America. The type section of the formation and 2 additional long sections in southern Illinois were chosen for study to show the nature of the youngest Chester conodonts of the area and to determine vertical variations in the fauna. The formation is divisible into 4 lithologic units, here referred to in ascending order as A, B, C, and D. The fauna of the lower 3 lithologic units is typically Chester in aspect but is definitive of the Kinkaid. Genera present are Cavusgnathus, Cladognathodus, Elsonella?, Falcodus?, Gnathodus, Hibbardella, Hindeodella, Lambdagnathus, Ligonodina, Neoprioniodus, Ozarkodina, and Spathognathodus. Some elements in unit C are interpreted as migrants, and these serve to distinguish the unit. Unit B differs from the other 2 units in the sparsity of conodonts found in it. The fauna of unit D is strikingly different from that of the lower 3 units and includes the additional genus Streptognathodus which composes over one-third of the fauna. Cladognathodus, Elsonella?, Gnathodus, and Lambdagnathus were not found in unit D. Other differences between the lower 3 units and unit D are related to differences in species and relative abundances of species. The unit D conodonts have affinities with both the Mississippian and the Pennsylvanian, and its stratigraphic placement must remain an open question. As an adjunct to the stratigraphic studies, the new species Streptognathodus unicornis and Falcodus? alatoides are named.

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