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15 - Middle Devonian Arkona Shale of Ontario, Canada, and Silica Shale of Ohio, USA

Published online by Cambridge University Press:  10 November 2010

Hans Hess
Affiliation:
Basel Natural History Museum, Switzerland
William I. Ausich
Affiliation:
Ohio State University
Carlton E. Brett
Affiliation:
University of Cincinnati
Michael J. Simms
Affiliation:
Ulster Museum, Belfast
Carlton E. Brett
Affiliation:
University of Cincinnati, Ohio
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Summary

The two related fossil assemblages discussed in this chapter occur in possibly age-equivalent Middle Devonian mudstones in southern Ontario and Ohio (Fig. 137). The Arkona Shale is exposed along the banks of the Ausable River and in its tributary streams in the vicinity of Arkona, Lambton County, Ontario, Canada. The Silica Shale is exposed in the quarries of the Medusa Cement Company and the New Genstar Cement Company, both north and south of Centennial Road in the town of Silica, Lucas County, Ohio. These mudstones are considered to be in the lower part of the Hamilton or Traverse Group and are of Early Givetian age, approximately 385 million years before present.

LIMESTONE LENSES WITH BRYOZOANS, BRACHIOPODS, TRILOBITES AND COMPLETE CRINOIDS

The thin skeletal limestone lenses within the Arkona and Silica Shales carry a moderately diverse fauna of bryozoans, brachiopods, gastropods, bivalves and trilobites, as well as crinoids and blastoids. Approximately 40–50 species can be found with considerable effort. The Silica fossils are described in a richly illustrated volume compiled by Kesling and Chilman (1975). Among the most common fossils are the stick-like bryozoans, Sulcoretepora, as well as Fenestella. Brachiopods include abundant, small, concavo-convex chonetids and Mucrospirifer. The trilobite Phacops is also commonly associated and has been found in clumps of articulated individuals in the Silica Shale of Ohio; it has become the landmark of these strata and is a highly valued collector's item. The surrounding mudstones are quite sparsely fossiliferous, but do occasionally contain isolated specimens of chonetids, Mucrospirifer and other brachiopods. Scattered, pyritized specimens of small bivalves (nuculids), goniatites and bactritids also occur.

Type
Chapter
Information
Fossil Crinoids , pp. 129 - 134
Publisher: Cambridge University Press
Print publication year: 1999

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