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2 Geological Quarterly

2 2007

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Limitations on the application of the Devonian standard conodont zonation

Bultynck P.

Geological Quarterly

2007

Vol. 51, No 4

339-344

The most commonly used Lower and Middle Devonian conodont zonations that some times have been presented as standard zonations are evaluated. The author questions whether the Frasnian standard conodont zonation based on a phylogenetic succession of species belonging to the pelagicgenera Mesotaxis, Palmatolepis and Siphonodella can be used for world wide correlation. He fa vours the idea of an in ter national cono dont ref er ence scale based on a syn the sis of well established and documented conodont successions (with figured specimens of first and last occurrences of index-species) from key areas representing a variety of facies. Graphic correlation is likely to be the most objective and precise method to provide such a synthesis represented by the composite standard. Such standards have been allready elaborated for the Frasnian and the Middle Devonian. This point of view does not imply that classical biozonations should be abandoned.

Conodont-based graphic correlation of upper Givetian-Frasnian sections of the Eastern Anti-Atlas (Morocco)

Gouwy S., Haydukiewicz J., Bultynck P.

Geological Quarterly

2007

Vol. 51, No 4

375-392

A high-resolution correlation of ten upper Givetian-Frasnian sections spread over the differ ent facies environments of the Eastern Anti-Atlas (Morocco) is established using graphic correlation. The mea sured strati graphic ranges of eighty-five cono dont taxa have been as sem bled into a chronostratigraphic framework. The developed regional composite subdivides the Frasnian into 501 composite standard units (CSU) based on the original thickness of the reference section (Bou Tchrafine). This is a higher resolution than obtained by the classic biozone correlation. Based on the conodont data available for this correlation project, the jamieae and Lower rhenana zones could not be recognised in the sections.