CHAPTER 6. DEVONIAN FOSSILS 



Collecting Localities 



In the curving band of Devonian exposures that runs from south-central to northeastern 

 Ohio (see map, fig. 8), collecting localities are so numerous that specific discussion of them 

 is not necessary. Numerous quarries have been opened in this area and many of them are 

 still good collecting grounds. The same is true of the creeks and runs that flow into the 

 Scioto and Olentangy Rivers. 



Over most of the state the Devonian rocks comprise four formations; the Columbus and 

 Delaware limestones below, and the Olentangy and Ohio shales above. Several thin "Bone Beds" 

 (Wells, 1944) occur in the limestones. These interesting layers are packed with tiny scales, 

 spines, and teeth of fish. They also contain abundant foraminifera, scolecodonts, ostracodes, 

 and plant spores. Such concentrations of fossil material have been explained as marking times 

 of pause in deposition and a slight erosion of the sea bottom, washing away the mud by gentle 

 wave action and leaving the fossils behind. Although bone beds are more or less local phenom- 

 ena, the stratigraphic positions of several of the major ones are well established and they have 

 been mapped over considerable areas. One of the best known bone beds is that at the top of the 

 Columbus limestone in central Ohio. Another is about 25 feet above the base of the Delaware 

 limestone in a layer containing abundant specimens of the "button coral," Hadrophyllum 

 d'orbignyi . " Another bone bed is exposed in the quarries at East Liberty, Logan County, in the 

 top of the Columbus limestone where this formation is overlain dis conformably by the Ohio shale. 



Devonian rocks are exposed in several northwestern Ohio counties. The Dundee limestone 

 throughout this area yields abundant fossils; an example is the Whitehouse quarry, near White - 

 house, Lucas County, and there are several others. 



The most attractive locality, from the paleontologist's standpoint, is Silica, Sylvania Town- 

 ship, Lucas County, where the Silica formation (named for the village) crops out. The quarries 

 are north of the village of Silica and have yielded beautifully preserved and abundant fossils for 

 many years. Permission of the quarry owners MUST be obtained before entering them. Some 

 of the best collecting is to be found in the older parts of the quarry, where the rock has been 

 weathering for a long time and loose specimens can be picked up. The fauna of the Silica forma- 

 tion has been described by Stewart (1927, 1930, 1940) and her works should be consulted for 

 further details. The lower part of the Silica formation is called the "Blue limestone" in older 

 publications. Detailed descriptions of the localities in this area will be found in Ehlers, Stumm, 

 and Kesling (1951). 



The Commoner Fossils 



PLANTS. Plant remains are extremely rare in our Devonian marine limestone and limy 

 shales. They are found occasionally but are too poorly preserved for identification. 



In the Devonian black shales, tree trunks, branches, twigs and spore -like fossils are abun- 

 dant in places. The tree trunks usually can be identified with the genus Callixylon and specimens 

 2 to 3 feet in diameter have been found. Branches and twigs of smaller size, 3 to 4 inches in 

 diameter, squashed flat but still recognizable, are common in parts of the Ohio shale. The nu- 

 merous ridges across the branches are characteristic. See Berry (1932); Hoskins and Blickk 

 (1940). 



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