﻿264 NEW YORK STATE MUSEUM 



oped along the margins of the granodiorite masses where they cut 

 into the banded Fordham gneiss. 



The essential feature of the rock is its fresh and sound char- 

 acter. This rock is not decayed. 

 5 Interpretation 

 a Drift 



The glacial drift and soil cover the bed rock at this point for a 

 depth of at least 195 feet. 

 b Residuary soil 



Decayed residuary matter of local derivation is detected at 212 

 feet. 

 c Bed rock 



The decayed matter still preserves the bed rock structures in a 

 sample taken at 347 feet. From this point downward there 

 is decayed rock ledge gradually becoming more substantial 

 d Formations represented 



After bed rock is reached the first 100 feet is so altered that 

 identification is not certain. At 350 feet, however, the cal- 

 careous nature of some of the material is observed, and on 

 this ground largely it is believed that an interbedded lime- 

 stone layer is penetrated down to about 377 feet. 

 From that point (377 feet) the material is very silicious and 

 not at all calcareous and the core when obtained is distinctly 

 gneissoid. This lower portion below (377 feet) is therefore 

 judged to be typical Fordham gneiss. 

 The bottom material is sound but a very rare variety for this 

 formation. 

 e Character of contact 



Normally the interbedded limestone lies conformable to the 

 structures and beds of Fordham gneiss. The structure in 

 such pieces as show it indicated a dip of about 70-80°. 

 Therefore the formation must stand very steep. But, so far 

 as can be seen in the fragments secured, there is no direct 

 evidence of a fault contact or anything abnormal. The ex- 

 tremely deep alteration of the rock is the chief unusual fea- 

 ture. It seems to require a better chance for water circula- 

 tion than is natural in the undisturbed rock of either forma- 

 tion. For this reason, I am of the opinion that there has 

 been movement in this zone that weakened the rock enough 

 to encourage water circulation. 

 The formation dips west in normal manner at about 75 degrees. 



