Biostratigraphy, Taxonomy, and Paleogeography of Conodont Sequences in the Middle and Late Devonian (Frasnian) Tropics

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Frasnian conodont sequences in the Montagne Noire and Alberta are superbly developed in their biostratigraphic continuity and excellent preservation of faunas representative of the Palmatolepis biofacies. Through graphic correlation, the sequence composited from these two areas will become a standard of reference for this biofacies, characteristic of outer shelf to basinal sequences throughout the inferred Devonian tropics. There has been great inconsistency in published identifications of species of Palmatolepis and Ancyrognathus resulting in erroneous understanding of ranges of the two principal groups on which the Frasnian "standard" zonation is based. Furthermore, there has been little study of the Polygnathus biofacies, characteristic of inner shelf Frasnian sequences. My research based on multielement taxonomy and shape analysis of platform elements has drastically revised discrimination of species of Palmatolepis and Ancyrognathus and consequently their stratigraphic ranges. The result is a near doubling in number of zones within the Palmatolepis biofacies, but their resolution is far exceeded by that obtainable through graphic correlation. Correlation between the Palmatolepis and Polygnathus biofacies remains difficult, but is probably resolvable through graphic methods. Proposed research will rigorously test these new biostratigraphic and taxonomic results in widely scattered localities throughout the Devonian tropics, with the additional long-range purpose of developing a comprehensive analysis of Frasnian conodont paleogeography.