22 NEW YORK STATE MUSEUM 



discontinuous deposits laid down on a broken coast line. The con- 

 tinuation of these sands westward into Erie county is striking evi- 

 dence of the increasing transgression of the early Devonic deposits 

 over the Siluric lands. 



In a number of places there is a mingling of the Oriskany sand 

 and phosphatic nodules through the bottom part of the overlying 

 Onondaga limestone, and in some places there are fragments of 

 the underlying Helderbergian limestones embedded in the Oriskany 

 or with the Oriskany sand embedded in the Onondaga limestone. 



The Oriskany sandstone has no commercial value in the Syracuse 

 area, since the bed is too thin and the rock too friable for building 

 stone and it contains too much iron for glass sand. In the Juniata 

 valley in central Pennsylvania it is used in large quantities for glass 

 sand. There it is several hundred feet thick and almost free from 

 iron. In some localities in Pennsylvania it is used in limited quan- 

 tities for the phosphate content for fertilizer. 



ONONDAGA LIMESTONE 



The term Onondaga limestone includes that great mass of lime- 

 stone about ioo feet thick between the Oriskany sandstone below 

 and the Marcellus black shale above. It now embraces all the terms 

 formerly designated by the names Onondaga, Corniferous and 

 Seneca. The name was improperly applied by Dana and by some 

 of the older writers to the salt and waterlime groups of the Salina 

 period. 



The lower portion of the limestone mass is known among the local 

 quarrymen as the " gray limestone." It has a pronounced crystalline 

 texture and, if it were white or bright colored, would pass in the 

 market as marble. It has a thickness varying in this vicinity from 

 10 to 30 feet, and occurs in fairly heavy beds from 1 to 4 feet or 

 more in thickness. It is quite fossiliferous throughout the area, con- 

 taining many well-preserved corals, crinoid stems, brachiopods, gas- 

 tropods, bryozoans and trilobites. The corals are especially abundant 

 so that in many places it suggests a coral plantation. The fossils 

 are calcite like that of the inclosing rock and are difficult to separate 

 from the matrix without fracturing them. They are a little more 

 resistant to the agents of disintegration than the matrix, become 

 easily affected by secondary silicification and hence stand out in 

 relief on the weathered surfaces. 



The Onondaga limestone is the most durable rock in the section 

 and hence stands out in bolder relief on the surface than any of the 



