BUFFALO SOCIETY OF NATURAL SCIENCES 11 



Cobleskill Limestone. 



The Cobleskill limestone is a layer of limestone lying 

 beneath the thin, shaly stratum representing the Oriskany 

 horizon and separated by this shale from the overlying lower 

 layers of the Onondaga limestone. It is the uppermost member 

 of the Siluric system. Its contact with the overlying beds of the 

 Devonic system is unconformable. 



This limestone is the upper portion of the Waterlime group 

 of Vanuxem and Hall. It was called the Coralline limestone by 

 Gebhard and Hall. It was referred by Clarke and Grabau to the 

 Manlius limestone. In 1902 Hartnagel considered it a western 

 extension of the Cobleskill limestone, named from Cobleskill 

 creek, Schoharie county. Amongst quarry owners and workers 

 it is known as "bull-head rock." 



In Ohio this formation is included in the Columbus 

 (Onondaga) limestone (Stauffer, Geol. Sur. Ohio, 4th series, 

 Bulletin 10)- The eroded surface that marks the junction of the 

 Cobleskill and the overlying Onondaga in Erie county does not 

 exist in Ohio. Instead there is an eroded surface in all ways 

 similar at the base of the Columbus limestone This disconformity 

 is regarded as marking the junction of the Siluric and Devonic 

 systems. Therefore the Cobleskill of Erie county which is below 

 this inconformity has been placed in the Siluric, although the 

 similar beds in Ohio are placed in the Devonic. This inconsistency 

 makes our present classification of these beds unsatisfactory. 



The Cobleskill limestone in the exposures in Erie county is 

 dark when freshly exposed and presents in a cross section a 

 distinctly banded effect, its light surface being crossed by darker 

 bands. It becomes lighter under the weather and after long 

 exposure turns to a buff or even light yellow. It is saccharoidal 

 and porous, and contains numerous, small, irregular cavities lined 

 or partly filled with calcite crystals. These cavities seem to be in 

 most cases molds of small corals, Cyathophyllum, hydraulicum, 

 which have been dissolved out. The rock burns to a natural 

 cement and has been quarried and burned in Buffalo for this 

 purpose since 1850 and in Erie county at Williamsville since 1825. 



The Cobleskill limestone may be seen to advantage in 

 quarries at many points along the " Ledge." Its best exposures 

 f 1913) are in the Barber Asphalt Company's quarry on Fillmore 

 Avenue, Buffalo, and at the Lockwood quarries east of Akron. 



