The optimal number of carboniferous series and stages

Reflexions on Frasnian and Famennian stage boundary decisions as a guide to future deliberations

The pros and cons of the three conodont-based boundaries of the Frasnian and Famennian Stages and their corresponding GSSPs (Global Stratotype Section and Point) are evaluated in terms of current taxonomic, biostratigraphic, and sedimentologic knowledge. Two of these boundaries are based on easily identified pelagic species, which provide excellent bases for global correlation. The third, for the base of the Frasnian, is based on a neritic species, whose taxonomy has been heatedly debated. The GSSPs for these three levels are all located in the Montagne Noire of southern France, partly because of political motivation to balance GSSPs selected in other regions. All three GSSPs are at levels from which global correlations cannot be effectively accomplished without aid from other, more complete sections or without making correlations strictly on the basis of taxonomic concepts - i.e., the entry of the definitive conodont species. Future deliberating bodies may want to reconsider the species chosen to delimit the base of the Frasnian and to select better GSSPs for all three boundaries.