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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 53 (1969)

Issue: 3. (March)

First Page: 723

Last Page: 724

Title: Significance of Provincialism in Richmond (Upper Ordovician) Correlations: ABSTRACT

Author(s): Herbert J. Howe

Article Type: Meeting abstract

Abstract:

Richmondian strata have been recognized in large areas of North America. Study of brachiopod faunas provides a basis for evaluating Richmondian correlations and the extent to which provincialism characterizes separate but supposedly time-equivalent sedimentary basins.

A comparison of the brachiopod faunas of the standard Richmond section with the nearby Maquoketa Shale shows a marked dissimilarity between the two. Of 14 diagnostic species common to the type Richmond (Ohio Valley), only three are found in the Maquoketa sections in Iowa. Of 13 diagnostic species common to the Maquoketa, only two are found in the

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type Richmond, whereas 12 species are shared by the Aleman and Cutter Formations (Texas and New Mexico) and six with the Arnheim and Fernvale Formations (Central basin of Tennessee). The evidence demonstrates a strong provincial aspect for the type Richmond fauna. The Maquoketa fauna is more widespread and provides a better standard for comparison.

The absence or scarcity of certain genera and species in one area is difficult to explain in view of their abundance in supposedly equivalent beds in the other. New studies show that the apparent absence of a species possibly can be explained by subspecific variation from one sedimentary basin to another, e.g., Plaesiomys subquadrata Hall.

The Arnheim and Fernvale faunas of Tennessee apparently occupy an intermediate position between those of the Maquoketa Shale and the Ohio Valley as they contain both unequivocal Maquoketa elements and diagnostic type Richmond forms.

Additional work is needed before the succession and lateral distribution of Upper Ordovician brachiopod faunas are clearly established.

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Copyright 1997 American Association of Petroleum Geologists