FOLIATION IN THE PRE-CAMBRIAN OF NEW YORK 605 



of flat-lying gneiss the dip .... is generally outward in all direc- 

 tions. The batholiths, therefore, are undoubtedly formed by an 

 uprising of the granite magma, and these foci indicate the axis of 

 greatest upward movement, and those along which the granite 

 magma has been supplied most rapidly." 1 



There are not only important variations from the general 

 northeast-southwest arrangement of the region within the quad- 

 rangles themselves, but also much broader variations shown 

 by a comparison of the average foliation strikes of all the quad- 

 rangles of the Adirondacks which have been mapped in detail. 

 This is graphically presented by the accompanying sketch map. 

 Such marked differences in foliation directions on large scales 

 throughout the Adirondacks is certainly incompatible with any 

 idea of thoroughgoing compression of the region. Thus in the 

 Lake Pleasant, North Creek, Blue Mountain, and Saratoga 

 quadrangles the foliation, either wholly or largely, strikes at high 

 angles across the general northeast-southwest strike of the 

 region, while in the Lake Placid quadrangle the strikes are 

 exceedingly variable. If due to compression, the foliation 

 strikes would be much more nearly northeast-southwest than they 

 actually are. 



Flow structure character of foliation. — Another significant feature 

 of the foliation should be mentioned, namely, that, while all the 

 minerals are arranged with long axes roughly parallel to the direc- 

 tion of foliation, the dark-colored minerals which accentuate the 

 structure most often appear as narrow, irregular, wavy streaks 

 which are seldom continuous for more than a few inches or a foot. 

 In the writer's experience this type of foliation is by far the most 

 common in the syenite-granite series, and it is believed to be the 

 result of magmatic flowage. Lawson has noted an exactly similar 

 phenomenon in certain granite gneisses of the Rainy Lake region 

 of Ontario and says: "The lines of streaking are very often not 

 straight but are wavy or contorted, sometimes intricately so, and are 

 evidently due to flow movements in the magma prior to its final 

 consolidation." 2 As already suggested, flow structures are locally 



1 Adams and Barlow, Geol. Surv. Can., Mem. 6, 1910, p. 14. 



2 A. C. Lawson, Geol. Surv. Can., Mem. 40, 1913, p. 93. 



