48 NEW YORK STATE MUSEUM 



An interesting assemblage of rocks is well exposed on the steep 

 hillside one-half of a mile north-northwest of Bailey pond. Com- 

 monest of all is good Whiteface anorthosite, but some tongues or 

 dikes of granite cut through it, and still other rock is quite cer- 

 tainly an assimilation product of the two, that is to say, Keene 

 gneiss. Most of the rock taken to be Keene gneiss is of syenitic 

 aspect both with and without quartz, but some contains pheno- 

 crysts of labradorite. No. 27 of table 3 represents a thin section 

 of this Keene gneiss, but the labradorite does not show in the thin 

 section. 



Still other local developments in the large area of " anorthosite 

 and syenite-granite mixed rocks " are described below. 



A number of small (not mappable) inclusions of Whiteface 

 anorthosite occur in the granite along the western side of the Beech 

 hill Whiteface anorthosite area. The borders of these inclusions 

 have been fused and assimilated by the granite which shows curved 

 flow-structures around the inclusions. 



Interesting exposures occur in the small area of Whiteface 

 anorthosite and syenite mixed rocks near the southeastern base of 

 Severance hill. The rock is mostly quartz syenite (no. 49 of 

 table 2) which contains numerous inclusions of Whiteface anortho- 

 site. These inclusions are very irregular and usually only a few 

 feet long without sharp boundaries against the syenite. Evidently 

 syenite magma rising through Whiteface anorthosite caught up 

 numerous small fragments of it, the borders having been assimilated 

 to form Keene gneiss on small scales. 



On large scales the geologic map shows two areas of Keene 

 gneiss, one occupying about 6 square miles, and the other nearly 

 3 square miles, in the central portion of the quadrangle. Before 

 the intrusion of the large gabbro stock, the two areas were prob- 

 ably connected with a total length of 7 miles, extending from 

 Rogers pond to and beyond Bailey hill. These bodies of Keene 

 gneiss lie mostly against typical Marcy anorthosite, but also, to 

 some extent, against Whiteface anorthosite, the border facies of 

 the anorthosite here having been very largely assimilated by the 

 syenite-granite magma. Throughout the larger area especially, 

 there are a good many small masses of Whiteface anorthosite, a 

 few of sufficient size to be mapped. There are also some outcrops 

 of fairly good granite and granitic syenite, thus showing that all 

 the original Whiteface anorthosite was not assimilated. The main 

 body of the rock is, however, quite typical Keene gneiss, there being 



