GEOLOGY OF THE LAKE PLACID QUADRANGLE 55 



Grenville due to cutting to pieces of the Grenville by the anor- 

 thosite magma along the border. This rock is not separately repre- 

 sented on the geologic map. - 



In the area of Whiteface anorthosite along the river west of 

 Malcom pond several ledges exhibit Grenville closely involved with 

 the anorthosite. 



Grenville or amphibolite and syenite-granite mixed gneisses. 

 In five areas shown on the map, the Grenville or amphibolite and 

 syenite or granite are so closely associated that the delimitation of 

 these rocks was not found to be practicable. 



The area bordering Lake Placid on the east shows, along the lake 

 shore, some ledges of pink granitic syenite with many long, narrow 

 inclusions of dark hornblende gneiss roughly parallel to the foliation. 

 Toward the interior of the area, there are some outcrops of nearly 

 pure granite syenite, and others which are very gneissoid, rather 

 basic looking, almost banded syenitic rocks which have resulted 

 from more or less fusion of layers of dark gneiss by the syenitic 

 or granitic magma. In some of these ledges there exist rather 

 well-defined bands or layers of dark gneiss not over a foot thick 

 where fusion has not been so effective. 



At the map edge southwest of Keene, the area of mixed gneiss 

 seems to show a predominance of syenite, but there are a good 

 many outcrops of light and dark-gray Grenville gneisses. In some 

 exposures the syenite and Grenville are rather closely associated, 

 but, as a rule, the relationships of the rocks are not well exhibited. 



One mile northeast of Keene the small area of mixed gneisses 

 well exhibits intimately associated Grenville light and dark gneisses 

 and syenite. Streaks and bands of Grenville are in some places 

 more or less fused in. 



In the area 2 miles a little west of north of Keene, syenite pre- 

 dominates, but considerable quantities of Grenville are involved 

 with it, often having been more or less fused in. On top of the hill 

 there seems to be a little Whiteface anorthosite as bands or inclu- 

 sions parallel to foliation of the syenite. 



The whole hill north of Cranberry pond is a mixture of fine to 

 medium-grained, gneissoid, pink granite and hornblende gneiss, 

 sometimes one and sometimes the other predominating. The horn- 

 blende gneiss (or amphibolite) occurs as bands in the granite par- 

 allel to the foliation. This dark gneiss is either Grenville or meta- 

 gabbro, probably the latter. 



Whiteface anorthosite and syenite-granite mixed gneisses. 

 Four areas of mixed rocks of this sort are shown on the geologic 



