214 



Report of the State Geologist. 



In the Livonia shaft it formed a green and brownish nodular layer four 

 and one half feet thick and carried fossils which indicated that it represented 

 also the arenaceous sedimentation of the lower part of the Onondaga or Upper 

 Helderberg formation. At the other shafts there is only a trace of it in the 

 condition of a greenish nodular parting in the limestones. 



Owing to the difficulty encountered in drilling it, this rock is readily 

 recognized by well drillers whenever present. in any appreciable thickness, as 

 it usually is in the eastern part of the salt district. 



At Tully it is fifteen to eighteen feet thick, and in the Ithaca test 

 well thirteen feet. 



Onondaga limestone. This formation is composed of layers from one inch 

 to three feet thick of light, bluish grey, compact limestone, separated by thin 

 partings of carbonaceous shale. In the eastern part of the salt district it has 

 a total thickness of sixty to seventy feet, which is gradually increased to about 

 145 feet in Genesee county. 



It is abundantly exposed along the rocky east and west ridge known as 

 the Helderberg escarpment, of which it usually forms the crest, and the Lower 

 Helderberir or Water-lime rocks the base. 



In the reports of the Geological Survey of the Third and Fourth Districts, 

 this mass of limestones was separated into two divisions, the lower being 

 designated the Onondaga limestone, on account of its abundant exposure in 

 Onondaga county, and the upper called the Corniferous limestone because 

 of the presence of hornstone or chert in layers and nodules throughout the 

 beds. This division has not of late years been generally recognized nor is it 

 practicable except locally, and the entire formation has been more commonly 

 known as the Corniferous or Upper Helderberg limestone. 



The chert is quite unevenly distributed through the limestones, and at 

 nearly every exposure, some layers are almost entirely free from it and are 

 quarried largely for building and ornamental purposes. When dressed it has 

 a semi-crystalline appearance, is handsome and durable. Large quantities of 

 quick-lime are also made from it. 



The extensive quarries on the Indian Reservation south of Syracuse are 

 in this rock. It is also extensively quarried at Auburn and at Le Roy, and less 

 extensively at Caledonia, Honeoye Falls, Phelps and other places. 



To the drillers of salt wells the "top of the hard limestone " is an easily 

 recognize*! bench-mark throughout the entire district, by which they know 

 that the bottom of the soft shales has been reached, and that there remains 

 500 to 550 feet of rock to be penetrated before the salt bed is reached, nearly 



