14 NEW YORK STATE MUSEUM 



rock was formerly quarried both for building stone and for burn- 

 ing. In the ledges of the creek above the quarry are some of the 

 higher cherty layers. 



For the most part however the formation is buried under the 

 drift and from this point to the western limit of the sheet no 

 other outcrop has been found. 



The higher layers of the limestone, lying with glaciated surface 

 beneath the soil cap, are seen in the old Giddings quarry, now 

 known as the Bacon quarry just to the east of the edge of the 

 map. 



In general it may be said that this formation forms the most 

 important repository of valuable building material within the 

 region covered by the map, and furthermore in the harder chert 

 layers is a convenient and inexhaustible source of road material 

 not inferior in quality to the field stone that has been generally 

 utilized in the county in recently constructed roads. 



Marcellus shale 



The term Marcellus shale has been generally applied in New 

 York geology to a black and dark blue shale formation lying im- 

 mediately on the Onondaga limestone. The lower boundary of 

 the formation is always perfectly clear but not so with the upper, 

 for the mass passes gradually into the lighter gray shales of the 

 Hamilton group above. At Marcellus village, Onondaga co., 

 from which place the name is derived, only the lower layers of 

 this black shale are well exposed and our observations both in 

 that region and thence westward indicate the desirability of re- 

 stricting the term Marcellus to these lower shales, which are 

 typically exemplified in the original locality but are better 

 delimited upward in Ontario county by the presence here of a 

 limestone cap — the Stafford limestone. Using the term in this 

 restricted sense the Onondaga limestone is overlain everywhere 

 by black slaty shale with a few thin calcareous layers and rows 

 of spheric calcareous concretions. The shales are highly im- 

 pervious and argillaceous and withstand exposure so well that 

 their outcrops are usually vertical or overhanging cliffs in a 



