The graptolite correlation of the North American Upper Ordovician Standard

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Abstract
The North American Upper Ordovician reference standard, the Cincinnatian Series, contains rich shelly and microfossil faunas in its type area in the Cincinnati Region but graptolites are uncommon in most of its shallow-water calcareous sediments. Consequently, the graptolite correlation of this key sequence has remained uncertain and, it part, even controversial. A review of both previously published and recently discovered graptolite occurrences in the type Cincinnatian, combined with data from the important graptolite successions in Oklahoma [USA] and New York-Quebec [Canada], has not only clarified the graptolite correlation of the Cincinnatian but also added new data on the morphology and taxonomy, and the vertical and horizontal distribution, of several taxa. The information now at hand indicates that the Edenian Stage correlates with the Climacograptus spiniferus Zone, the Maysvillian Stage with the C. pygmaeus and lower and middle Amplexograptus manitoulinensis Zone, and the Richmondian Stage with the upper A. manitoulinensis, the Dicellograptus complanatus; and possibly part of the C. inuiti Zone. Comparison between graptolite and conodonot biostratigraphic evidence reveals no apparent conflict. Correlations are proposed between Upper Ordovician North American stages, graptolite and conodont zones, successions in Texas, Oklahoma, and Sweden, European graptolite zones, and British series.