GEOLOGY OF THE AUBURN-GENOA QUADRANGLES 1 5 



but the number of species is quite limited. The more prominent and 

 persistent forms occurring in this rock in the central part of New 

 York are : 



Spirifer arenosus (Conrad) Hipparionyx proximus Vanuxem 



S. murchisoni Castelnau Chonostrophia complanata Hall 



Rensselaeria ovoides (Eaton) Meristella lata Hall 



Onondaga limestone 



The heavy beds of bluish gray limestone with embedded nodules 

 and nodular layers of chert or hornstone overlying the Oriskany sand- 

 stone and succeeded by the black Marcellus shales, was designated 

 " Cornitiferous limestone " by Prof. Amos Eaton in 1839, and in the 

 early reports of the Geological Survey was considered in two di- 

 visions. The basal member, which is usually free from chert and but 

 a few feet thick is the " grey sparry limestone " of the annual reports. 

 In his report on the Fourth Geological District (1839) James Hall 

 first used the term Onondaga limestone, applying it to this basal di- 

 vision of the formation. The overlying cherty beds composed the 

 " Seneca limestone " of the early reports and the '*'Corniferous lime- 

 stone " of the final reports of Hall and Vanuxem in 1842. 



The name " Onondaga Salt Group," applied to the Vernon and 

 Camillus shales, was used in the annual and final reports of the 

 Geological Survey but discontinued some years after. In Clarke 

 and Schuchert's revised '' Classification of the New York Geologic 

 Formations " the term Onondaga limestone is expanded to include 

 all of the strata between the Oriskany horizon and the Marcellus 

 black shales.^ 



The limestone is usually separated by thin partings of shale or 

 bituminous mud into even compact layers or tiers from 6 inches to 

 3 feet thick, some of which are nearly or quite free from chert and are 

 valuable as building stone, while others contain a considerable pro- 

 portion of the flint or hornstone and are utilized extensively when 

 crushed as road material. Shaly tiers occur at some localities but the 

 beds are mostly compact. The hundreds of quarries in the Onondaga 

 limestone along its line of outcrops from the Hudson valley to 

 the Niagara river attest its importance among the economic resources 

 of the State and show the enormous amount of this rock that has 

 been and is still being utilized. 



1 For a more detailed history of the names applied to this formation see 

 State Museum Bulletin 128. 



