r32 NEW YORK STATE MUSEUM 



The details of local geology were taken from the state map of 

 1S91. Till the topographic sheets from the U. S. geological survey 

 are available, it will hardly be feasible to perform more detailed 

 work, but with proper maps some slight rearrangement of bound- 

 aries may be possible. Meantime, the above notes will serve to 

 give some idea of the character of the gneisses. 



Mayfield 



Mayfield lies east of Bleecker and is a long, narrow town, 

 of which about half is gneiss and half paleozoics. The great 

 fault scarp, which begins at the " Xoses " on the Mohawk, passes 

 across the town in a northeast direction. On the southeast the 

 paleozoics have been dropped and preserved by the fault, while 

 on the northwest the gneisses have alone survived. Specimens 

 20 and 21 from the central part of the township are hard, dark 

 gray gneisses. When studied in their section they are not so 

 basic as they appear to the eye. Quartz is much the most abun- 

 dant mineral, biotite is next, and the remainder of the slide is 

 garnet and a little orthoclase. In the ridge along the eastern 

 border of the town the gneiss is lighter colored and is very finely 

 laminated. It has been very greatly crushed and rubbed out 

 into laminae, with much biotite along the surfaces of move- 

 ment. It apparently contains more feldspar than no. 21, but both 

 give a strong impression of being derived from altered sediments. 



Montgomery and Fulton counties 



The " Nose* " 



The exposures of the old crystalline rocks which are brought 

 to the surface by the combined anticline and fault at the 

 " Noses," on the Mohawk river, are of great scientific interest, be- 

 cause, except for the similar exposures at Littlefalls, they are the 

 last opportunities that we have to observe this formation, before 

 it dips beneath the great area of paleozoics. The " Xoses n is 

 the name given to the bold headlands which are situated between 

 Fonda and Canajoharie, and which rise from the Mohawk with 

 almost precipitous escarpments to a level of 500 feet above the 



