The biostratigraphy of the Nicolet River Formation in Quebec and intra-North American correlations in Middle and Upper Ordovician strata

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Abstract
At the present time, graptolites provide the only satisfactory biostratigraphical zonation of the Nicolet River Formation in Quebec. Five detailed sections of this formation show that it ranges in age from the Corynoides americanus or Orthograptus ruedemanni Zone to post-Climacograptus manitoulinensis Zone. Correlation of these strata with others in North America indicates that the bases of the Cobourgian (classical uppermost Champlainian) and Edenian (basal Cincinnatian) are not correlative, although these stages must be partially time equivalents; however, we have refrained from suggesting a new stadial term for these post-Shermanian but pre-Edenian strata. Our graptolite-based correlation of Berry's Zone 13 (Marathon region, Texas) with the eastern North American and western European successions differs from conodont-based correlations.