572 NEW YORK STATE MUSEUM 



GEOLOGIC DISTRIBUTIO]^ 



Olajs or shales occur in every geologic formation even in tlie 

 arcliean. It can be said in general that all those which are older 

 than the Cretaceous are shale, while those of Cretaceous and Ter- 

 tiary age are sometimes soft plastic clays, as those of ISTew Jersey 

 and Long Island, or at times shales, as exampled by the fire clays of 

 Colorado. 



The Quaternary deposits of clay are all unconsolidated, . so far 

 as known, no shales occurring in this formation. 



The geologic age of a claj- or shale is no indication of its com- 

 mercial value, except at most for the comparison of two deposits 

 in closely adjoining areas, but even here it is not safe to rely on 

 . such a guide. 



Those deposits which are of marine origin are commonly much 

 more extensive than those formed in inland waters. 



Occurrence of clay in New York state 



Deposits of clay or shale are to be found in nearly every county 

 of the state. They are divisible into the following classes. 



1 Residual clays Soft plastic clays 



2 Sedimentary clays Shales or consolidated clays 



1 Residual clays. Deposits of this type are rare in glaciated 

 regions ; still several small kaolin veins have been found to the 

 east and southeast of Sharon Station on the New York & Harlem 

 railroad, but it is doubtful if they will ever become of commercial 

 importance. They are also found in the adjoining portion of Con- 

 necticut, one being worked 4 miles east of Sharon. Residual 

 clays also occur in association with the limonite deposits at 

 Amenia, and in the vicinity of IsTew York city the dolomitic lime- 

 stones have by their decomposition sometimes given rise to clays 

 of a residual nature. 



