THE GEOLOGICAL HISTORY OF NEW YORK STATE 35 
large masses and lack of sharply defined bands of varying composi- 
tion. 
That these granite-syenite rocks are younger than the anorthosite 
is demonstrated by the fact that tongues of the former have 
been observed to cut the latter (see figure 12). Since the granite 
and syenite now visible in the Adirondacks are plutonic rocks, they 
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Fic. 13 Geologic and topographic sketch map of the southeastern portion 
of the North Creek sheet (Warren county), showing the surface relations 
of the common Precambric rocks in the southeastern Adirondacks. Con- 
tour interval roo feet. Horizontally lined areas —syenite or granite; blank 
areas — chiefly Grenville; small heavy black lines are faults. The faults 
here shown are minor ones which do not follow the NE-SW trend of the 
major faults of the eastern Adirondacks. The so-called “ patch-work” 
effect is well shown. Note how the more resistant rocks form the moun- 
tains which rise above the general level of the Grenville. (W. J. M.) 
could not have reached the surface by intrusion, as such rocks can 
be formed only by slow cooling under great pressure thousands of 
feet below the earth’s surface. They now appear at the surface be- 
cause of vast removal, by erosion, of the overlying original 
materials. 
2 
