12. 



NEW YORK STATE MUSEUM 



Phelps, 4 feet, 2 inches of sandstone. In the central and eastern 

 part of the State this formation is an interrupted deposit having 

 at^some exposures the character of an arenaceous limestone 1 to 3 

 feet thick while at Union Springs, Onondaga Valley, Oriskany 

 Falls and other localities it is a friable, light colored and rather 

 coarse sandstone containing an abundance of fossils. It attains 

 a thickness of more than 20 feet in, a lentil in the northeast corner 

 of the town of Skaneateles, Onondaga co. 1 



Onondaga limestone 



This important deposit is a compact, dark bluish gray lime- 

 stone bedded in layers from 3 inches to 2 feet thick and carrying 

 interbedded nodules and nodular layers of chert. 



The limestone contains a large amount of carbonaceous matter, 

 which appears in the shaly partings and on the surface of the 

 layers discoloring and giving them a black appearance. This 

 carbonaceous admixture is removed by slow decomposition on 

 exposure and the rock then assumes a very light bluish gray color. 



The chert, as a rule, is nearly black and slightly translucent, but 

 sometimes lighter colored and bluish. It is very unevenly dis- 

 tributed in the beds; in some it largely predominates and in others 

 it is entirely absent. It forms nodular layers which are frequently 

 continuous for long distances. Outcrops of these and boulders 

 of the cherty limestone that have been long exposed present a 

 peculiarly ragged and scraggly appearance, owing to the superior 

 resistance to decomposing agencies that the chert possesses over 

 the limestone. 



At some outcrops a very small portion of the formation is shaly, 

 but all of the remainder wherever the amount of chert is not too 

 large, is somewhat compact and durable and exceedingly valuable 

 as building stone and for the production of quicklime. 



At the base of the formation, filling the depressions in the Coble- 

 skill waterlime and varying greatly in thickness, there occurs a 

 stratum of limestone almost entirely free of chert, and embracing 

 lenses of considerable extent wholly composed of corals. 



The latter stratum is but 5 inches thick in the bed of Scaja- 

 quada creek at the Main street bridge; 7 feet in an old quarry in 

 Forest Lawn cemetery; 5 feet, 6 inches in the park quarry; 5 feet 

 in the southern part of the Buffalo Cement Co.'s quarry and less 

 than 2 feet in the northern. It is a veritable coral reef, 35 feet 



1 The9e lentils of sandstone in the strike of the Oriskany formation have been described by 

 Clarke. Amer. Ass'n: Adv. Sci. Proc. iooo; Science. Dec. a8, 1900. 



