34 NEW YORK STATE MUSEUM 



these latter being chiefly dark hornblende gneisses and light-gray 

 quartz-feldspar gneisses arranged as bands, belts, or lenslike inclu- 

 sions in the igneous rocks and parallel to the foliation. In some 

 cases these belts or inclusions of Grenville merge into the inclosing 

 igneous rocks because of melting of their borders at the time of the 

 magmatic invasion. Though the outcrops are rather poor in many 

 portions of the area, it seems fairly certain that the granitic and 

 syenitic rocks predominate. 



A solid ledge for 200 yards in the gorge of Fishing brook just 

 east of the county line shows a preponderance of pink granite which 

 contains distinct belts of both dark and light Grenville gneisses 

 parallel to the foliation. 



Where the secondary roads diverge two-thirds of a mile west of 

 the Long lake bridge, there are fine ledges of rather variable rock 

 consisting in part of syenitic and gray granitic gneisses with dis- 

 tinct amphibolite and gray Grenville gneiss bands parallel to the 

 foliation. Much of the rock, however, is streaked to almost thin- 

 banded due to injection of the gneisses by thin layers of magma 

 (see plate 9). At one place a very small mass of Grenville lime- 

 stone was noted. 



On the shores of Long lake within one-half of a mile of the 

 northern map edge, there are fine exhibitions of typical mixed 

 gneisses. Thus on the eastern shore one-eighth of a mile southwest 

 of the small mapped Grenville mass, there is a big ledge of syenitic 

 to almost gabbroic looking gneiss with streaks, blotches and bands 

 of dark, biotite-garnet and gray, biotite-quartz gneisses arranged 

 parallel to the foliation. The southern portion of this ledge is pink 

 granite which merges (as a result of fusion) into a biotite-quartzite. 



The. end of the sharp point projecting into the lake less than one- 

 quarter of a mile southwest of the locality last described is a solid 

 ledge of mixed gneisses which looks as though Grenville strata 

 had been thoroughly cut up, and more or less fused, by the syenite 

 magma so that both Grenville and syenite often do not show their 

 typical features. 



In certain other ledges on the lake shores there is good evidence 

 for some fusion of Grenville strata, and frequently bands of 

 amphibolite up to 20 or 30 feet wide occur parallel to the foliation 

 of the syenitic or granitic gneisses. 



Other areas. In the bed of Rock river nearly i mile below the 

 outlet of Rock lake, large exposures show green pyroxene, white 



