Conodont zones recognized in the Brassfield Limestone and the Salamonie Dolomite (includes the Osgood and Laurel as members) in southeastern Indiana and adjacent Kentucky generally are comparable with Zone-I, the celloni- and amorphognathoides-Zones, and probably the patula-Zone established by Otto Walliser in the Carnic Alps. Differences in generic composition of the European and Midwestern faunas and apparent range extensions suggest a more complex zonation than that established by Walliser.

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Although the conodont fauna of the Brassfield Limestone conforms in general with that of Zone-I, it appears to be transitional with the celloni-Zone fauna in southeastern Indiana, where the formation is younger than in its type area in east-central Kentucky. Correlation with the European sections is made more difficult because specimens assigned by Walliser to Icriodina irregularis and considered by him to be indicative of the upper part of Zone-I may in fact belong to Scyphiodus, a genus that is present in beds as young as the lower part of the Clinton Group in Ontario. A new platform-type genus derived from Spathognathodus is first recorded in the upper part of the Brassfield.

Above the Brassfield Limestone in its classic concept is another lithologic unit, tentatively assigned to the Brassfield, that has a mixed conodont fauna. The conodonts considered indigenous include Icriodina irregularis, Hadrognathus staurognathoides, Carniodus spp., Spathognathodus celloni, Pterospathodus amorphognathoides, and new species thought to belong high in the celloni-Zone. Overlap of S. celloni and P. amorphognathoides shows extension of the known range of one or both species. The conodonts of this zone are morphologically unstable, but the thinness of the unit and admixed material, including Ordovician specimens, do not allow recognition as yet of precise evolutionary development and zonation.

The conodonts in the basal part of the overlying Salamonie Dolomite belong in the amorphognathoides-Zone and include Pterospathodus amorphognathoides and Ozarkodina gaertneri. In Europe the upper terminations of these two species and Carniodus coincide, whereas in the Cincinnati arch area the two extend considerably above the highest level of Carniodus. These facts suggest that an unconformity is present in the Carnic Alps between the amorphognathoides- and patula-Zones. If so, most of the Salamonie above the lower beds that contain Pterospathodus may represent an unrecorded time interval, but it is possible that the absence of Kockella patula reflects provincialism.

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