30 NEW YORK STATE MUSEUM 



In the Schroon Lake quadrangle, a tongue of granite from 2 to 4 

 miles wide in the vicinity of Cheney pond extends into the anortho- 

 site for fully 4 miles, reaching all the way through the border 

 facies and into the Marcy anorthosite (see map). The large intru- 

 sive mass of later gabbro lies within this salient and cuts out much 

 of the originally present granite. Two of the small dikes of granite 

 above mentioned are off-shoots of this salient of granite in the 

 anorthosite. 



Inclusions of anorthosite in the syenite-granite. Inclusions 

 of anorthosite- in the syenite-granite series furnish very strong evi- 

 dence that the syenite-granite body is an intrusive distinctly sepa- 

 rate from, and later than, the anorthosite. Such evidence is 

 scarcely, if at all, mentioned by Bowen, probably because few 

 examples of such inclusions were known to him. Many excellent 

 examples have come under the writer's observation. 



It seems evident from a glance at the accompanying Schroon 

 Lake geologic map that the anorthosite once extended out as a 

 continuous broad belt at least 7 or 8 miles beyond the present 

 margin of the Marcy anorthosite because, within that distance 

 from the Marcy anorthosite, there are many inclusions of anortho- 

 site (mostly of sufficient size to be mapped) in the syenite-granite 

 series all the way across the quadrangle. In other words, only 

 mere remnants of the former anorthosite are now visible. With 

 the exception of one locality, these are all inclusions of Whiteface 

 anorthosite. The exceptional locality is of particular interest. It 

 is on top of Wilson mountain, and represented on the geologic map 

 as a small area of mixed rocks. One patch of the granite 12 feet 

 across contains large dark bluish gray labradorites an inch or more 

 across and several small pieces of typical Marcy anorthosite as 

 distinct inclusions, mostly arranged roughly parallel to the folia- 

 tion of the granite (see figure i). Immediately around the larger 

 fragments the granite exhibits fine magmatic flow-structure. A 

 similar exposure occurs close by. A reasonable interpretation is 

 that the granite magma moving upward enveloped two small masses 

 of Marcy anorthosite and tore them into small fragments which 

 became somewhat scattered and arranged parallel to distinct mag- 

 matic currents which moved up nearly vertically as shown by the 

 high angle of dip of the magmatic flow-structure foliation. 



A fine example is in the bed of the brook I mile southeast of the 

 summit of Oliver hill where a mass of Whiteface anorthosite 20 

 feet across is inclosed in the granite (see map). This outcrop con- 



