Evaluation of Possible Diachroneity in Homotaxial Mid-Carboniferous Ammoid and Conodont Successions, North American midcontinent, Western Europe, Russia

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9910456MangerBiostratigraphy of the Middle Carboniferous on a worldwide basis has relied on the well-documented successions of ammonoids and conodonts from the North American mid-continent, Western Europe, the southern Urals, Russia and the Donets Basin, Ukrainia. Based on the British ammonoid orthochronology established in the early part of this century, the North American midcontinent must be regarded as possessing a significant break at the Mississippian-Pennsylvanian boundary representing the missing Homoceras interval as it has been interpreted for nearly a century. Significant breaks in the succeeding Morrowan interval of North America are also necessitated by the missing representation of index species of the ammonoid genus Reticuloceras. If correlations between Great Britain and the North American midcontinent are based on a standard utilizing the first appearances of index conodont taxa, then the problem of a diachronous, yet homotaxial, succession is transferred to ammonoid occurrences. Acceptance of an isochronous conodont biostratigraphy also necessitates the presence of a significant, yet unrecognized, gap in the Pennine section of Great Britain. This gap would be filled by the lower Morrowan succession from the North American midcontinent based on conodont correlations. Resolution of the apparent diachroneity of the ammonoid and conodont successions is critical to the stated goals of the SCCS and IUGS in establishing a precise chronostratigraphy for the Carboniferous. Thus, evaluation of this problem with ammonoid/conodont diachroneity lies at the foundation of the entire chronostratigraphic framework for the Carboniferous (Mississippian/Pennsylvanian) System. This SGER will attempt to evaluate and resolve these critical correlations.