LIME AND CEMENT INDUSTBIES 753 



GEOLOGY OF NEW YOKK LIMESTONES 



Limestones are found in New York from the oldest to the 

 youngest formations. Some, like those of the pre-Cambrian, are 

 often local in their extent; while others, like those of the Helder- 

 berg, extend from one end of the state to the other. 



The formations containing limestone in New York state are 

 the pre-Cambrian, Calcif erous, Chazy, Trenton, Clinton, Niagara, 

 Onondaga, Lower Helderberg, Upper Helderberg, Goniatite, 

 Tully, Quaternary marls. 



The most important of these are the Calciferous, Trenton, 

 Niagara, Lower Helderberg and Upper Helderberg. The Calcif- 

 erous and Niagara sometimes contain sufficient magnesia to be 

 called true dolomites, and this fact, together with the freedom 

 from impurities which they exhibit at some localities, gives them 

 a special usefulness. 



Calciferous 



The rock of this formation is frequently highly magnesian, 

 and a high percentage of silica is likewise not uncommon in it. 

 On this account it is sometimes called Calciferous sandrock. 



The Calciferous limestones occur as isolated patches or belts 

 in several parts of the state, and show considerable variation in 

 character. With few exceptions they are magnesian and indeed 

 may pass into true dolomites. On the other hand, they are often 

 highly silicious, so much so as to render them practically worth- 

 less for any of the uses considered in this report. Again they 

 may run very low in silica, as near Glens Falls. 



Cambro-Silurian limestones appear in the southeastern portion 

 of the state in Orange county, extending northeastward across 

 the county to the Hudson river, and across it through Dutchess 

 into Columbia county. 



Another series of belts begins in Westchester county and ex- 

 tends from New York city northward to the county line and 

 through Putnam and Dutchess counties to Pawling and beyond. 



