FOLIATION IN THE P RE-CAM BRIAN OF NEW YORK 619 



coarser, less foliated rock may be readily interpreted as the result 

 of a forcing of slightly more liquid portions of the congealing magma 

 through more solidified portions. 



Highly developed "corrosion rims" are beautifully and exten- 

 sively developed in the Adirondack gabbros. 1 Their occurrence 

 even in non-foliated gabbro with diabasic texture argues strongly 

 for their production before final consolidation of the magma, this 

 possibility having been recognized by other investigators. How 

 could regional compression have caused so much of this sort of 

 granulation without otherwise affecting the rock ? Also, if granula- 

 tion of this sort has resulted from movements prior to solidification 

 of the magma, why could not the more general cataclastic textures 

 of the syenite-granite, anorthosite, and gabbro have been similarly 

 produced? As in the older intrusives, so in the gabbro, the 

 finer-grained more foliated portions are quite generally the most 

 granulated, this doubtless resulting from more pronounced flowage 

 movements in certain portions of the magma late in the process 

 of consolidation. 



1 W. J. Miller, Jour. Geo!., XXI (1913), 168-70. 



