GEOLOGY OF THE GENEVA-OVID QUADRANGLES 13 



It is 75 to 80 feet thick on this quadrangle and is composed of a 

 series of even layers 6 inches to 3 feet in thickness separated by 

 thin partings of shale or chert, these layers being usually divided by 

 vertical joints into large rectangular blocks. At the base a few 

 layers having usually a total thickness of 5 to 8 feet are composed 

 largely of corals and are specially desirable for house trimmings. 



Chert or hornstone, varying in color from black to light blue is 

 unevenly distributed through a considerable part of the higher beds, 

 occurring in nodular layers or rows of separate nodules, on the sur- 

 face of the strata or compactly imbedded within them. Fragments 

 of these cherty beds are scattered over the country south of the line 

 of outcrop to which the protruding flinty nodes give a peculiarly 

 scraggy appearance. 



While the layers that contain a considerable proportion of chert 

 are less valuable for building purposes, they afiford in unlimited 

 quantities the best quality of road metal found in western New 

 York. 



The area over which the Onondaga limestone is the surface rock 

 in the Geneva quadrangde is divided by the Seneca river about 

 equally, that part on the north side being mainly in a low flat region 

 in which the rock is entirely covered by drift or alluvium. 



A small outcrop of shaly limestone 2 miles north of Geneva 

 and west of the Auburn branch of the New York Central Railroad 

 is the only exposure of the Onondaga limestone on this quadrangle 

 north of the river and lake. In the region adjacent to the river on 

 the south side there is an average northward slope of 50 to 60 feet 

 per mile on the surface and the drift mantle being but a few feet 

 thick the rock appears in the fields and along the streams in many 

 places. 



The best exposures are afiforded by the extensive quarries of 

 which there are 10 or more in an irregular row beginning on the 

 river bank a mile west of Waterloo and extending toward tne 

 southeast to the vicinity of Canoga. The basal layer is exposed 

 slightly in AlcOuan's quarry and the cherty strata next above it at 

 the Waterloo dam. 



In the old quarry near the Lehigh Valley Railroad a mile west 

 of South W^aterloo, 25 feet of the beds just above the middle of 

 the formation may be seen and the same horizon is now exploited 

 in the Thomas Brothers quarry half a mile south of Waterloo; also 



