FOLIATION IN THE PRE-CAMBRIAN OF NEW YORK 603 



out batholiths and develop foliation after the consolidation of the 

 magmas, how are these sharp variations in strike of Grenville 

 inclusions to be accounted for? According to the writer's view, 

 such inclusions present no difficulties, because their foliation was 

 produced prior to the intrusions, and some fragments, especially 

 those caught up late in the stiff, nearly consolidated magmas with 

 poorly defined currents, would not have been swung into parallelism 

 in the uprising magmas. 



Also there are important exceptions to parallelism of foliation 

 of adjacent syenite or granite and Grenville gneisses in relatively 

 large areas. A few examples will suffice: eastern side of Port 

 Leyden quadrangle where Grenville with north-south strike is 

 surrounded with syenite with strike N. 30 E.; northwest corner 

 of North Creek quadrangle (see geologic map); near northeast 

 corner of Lake Pleasant quadrangle (see geologic map) ; northwest 

 of Indian Lake Village; one mile west of Long Lake Village; and 

 in the Broadalbin quadrangle where the large areas of Grenville 

 and adjacent syenite-granite show very different strikes. If the 

 foliation has been produced by compression after the intrusions, 

 how are such sharp differences in strike to be accounted for? 

 Granting the writer's conception that the Grenville was foliated 

 prior to the intrusions, and that the syenite-granite foliation was 

 the result of magmatic flowage, it is to be expected that the mag- 

 matic currents would occasionally have broken across the Grenville 

 and its foliation. 



Very strong evidence against the development of foliation by 

 compression of the great intrusives is the frequent occurrence of 

 sharp variations in the strike of the foliation, often within short 

 distances. Examination of the Long Lake, North Creek, and Lake 

 Pleasant geologic maps, upon which foliation strikes are plotted, 

 shows many strikes in granite or syenite ranging from parallel to 

 right angles to each other, often within distances of a mile or two. 

 Similar foliation variations occur upon the writer's Blue Mountain 

 and Lake Placid geologic maps, not yet published. How can such 

 foliation variations possibly be explained as due to lateral pressure ? 

 If due to compression of the whole region, should not the foliation 

 always strike essentially at right angles to the compressive force ? 



