geologic formations of new yoke 163 



Hamilton Shale 



The Marcellus shales change gradually at their higher part 

 into the Hamilton shale which is a harder, lighter colored mass, 

 often containing sandstones, and, in central New York and as 

 far east as the Catskill range, is 1,000 feet or more in thickness. 

 Like the Marcellus shale, many parts of it show few marks of 

 stratification; but it is divided vertically by joints, which, 

 where it is excavated, are often as upright and smooth as the 

 walls of a plastered building. In the more eastern part 

 of the state, it is generally coarse-grained and sandy; in western 

 New York, it is fine-grained, soft and more calcareous, forming 

 by its decomposition a rich soil. 



In the survey of the fourth district Hall divided the Hamilton 

 into three parts; at the base the Ludlowville shale, overlaid by the 

 Encrinal limestone and at the summit the Moscow shale. The 

 Ludlowville and Moscow horizons take their name from localities 

 in western New York. The Encrinal limestone is named from its 

 prevailing fossil. 



TULLY LIMESTONE 



The Hamilton group terminates in central New York with a 

 very impure dark limestone, about 10 feet thick, which received 

 its name from the village of Tully in Onondaga county. In the 

 eastern and western parts of the state this rock does not exist, 

 as it extends only from Ontario county to Madison, and beyond 

 these limits the Genesee slate lies directly on the Hamilton group. 

 The Tully limestone contains some fossils which are common to 

 it and the lower shales. 



Genesee 



The next rock in upward order is the Genesee, a series of layers 

 of thin-bedded, fissile, black slate, in some places 150 feet thick, 

 but diminishing westward so that it is only about 25 feet on 

 Lake Erie. It is, however, distinctly recognized in Pennsylvania, 

 where it is some 300 feet thick. It derives its name from one of 

 its best localities in this state, the gorge of the Genesee river 



