GEOLOGY OF THE NORTH CREEK QUADRANGLE 2^ 



gray, medium-grained, biotitic, granitic gneiss which is intimately 

 associated with some Grenville gneiss. Here again it is quite cer- 

 tain that the granitic gneiss forms a border zone between the gran- 

 ite porphyry and the Grenville, where the former has more or less 

 assimilated some of the latter. 



Along the southeastern base of Moon mountain there are excel- 

 lent exposures of Grenville much cut up by, and often fused into, 

 syenite. 



The mixed gneiss area at the southwestern corner of the map 

 affords many fine examples of syenite or granite and Grenville 

 closely involved and fused together. There are also many well- 

 defined inclusions or stringers of Grenville scattered through the 

 igenous rock. These phenomena are especially well shown on \\' olf 

 Pond mountain. 



The mixed gneiss area which surrounds Heath mountain con- 

 sists very largely of Grenville gneisses and limestones through 

 which numerous small masses of syenite or granite have been in- 

 truded. The most interesting exposures occur along the river 

 for nearly a mile northward from the Ferry. About i mile north 

 of the Ferry and on the east side of the river, are great ledges 

 of Grenville limestone and hornblende gneiss, these rocks being 

 badly contorted and broken and containing some patches of good 

 syenite, lo to 30 feet across, and completely surrounded by either 

 hornblende gneiss or marble. At the same locality a large mass of 

 syenite overlies crystalline limestone and shows the actual sharp 

 contact for fully 100 feet, there being no particular contact 

 phenomena (see plate 3). 



About one-half of a mile north of the Ferry, and along the road, 

 there are several very interesting inclusions of Grenville limestone 

 in the syenite. Two of these inclusions (one being 3 or 4 feet 

 across and the other 20 feet long and 2 to 4 feet wide) are com- 

 pletely surrounded by, and in very sharp contact with, the syenite. 

 The limestone is coarse, crystalline, calcitic, and contains graphite. 

 At the contacts small green pyroxene crystals are often common. 



The small area near Daggett pond is of interest because the 

 Grenville is there interbanded with granitic syenite, the bands of 

 each rock often being 20 to 40 feet wide and the contacts pretty 

 sharp. One Grenville band is a garnet, pyroxene gneiss, while 

 others are biotite or hornblende gneisses. 



The area of mixed gneisses lying to the east of Stockton and 

 Gage mountains shows numerous exposures of closely associated 



