I6 NEW YORK STATE MUSEUM 



This limestone appears to correspond with the lower part of the 

 limestone mass in figure i. 



There is no positive proof that the quartizite shown in figure 

 3 is the same as that of the lower part of figure i, but the two rock 

 masses are of much the same character and both are of great thick- 

 ness. This quartzite of figure 3, which represents a section across 

 the valley between Chase and Bull Rock mountains, is nearly pure 

 and shows a thickness of about 3000 feet with banded biotite-garnet 

 gneiss dipping under it on the west side. 



Figure 4 is another fine section of the quartzite which also shows 

 the underlying rock to be a banded biotite-garnet gneiss of unknown 

 thickness. 



The limestone of the Valentine pond valley appears to dip south- 

 ward under a thick belt of distinctly light and dark banded garnet 

 gneisses, but just where these rocks belong in the columnar section 

 can not be said. 



The quartzite in the area southwest of Thurman is often very 

 tremolitic, which suggests that it does not belong with the other 

 quartzit^s of the quadrangle. 



QUARTZ SYENITE 



As shown on the geologic map, the syenite covers about two- 

 ninths of the area of the quadrangle and is distributed in very 

 irregular shaped areas. Boundary lines between the syenite and 

 granite can not be sharply drawn because of the gradation of the 

 one rock into the other. Against the Grenville the boundary is 

 generally not very sharp except where the Grenville has been 

 faulted against the syenite. 



As regards granularity, structure and mineral composition the 

 syenite is a very variable rock. The granularity ranges from fine 

 to fairly coarse grain, with medium grain decidedly prevalent and 

 with only rarely suggestions of a porphyritic texture. Evidence 

 of crushing or granulation of the rock is common, especially in 

 the cases of the more acid (granitic) syenites where the feldspars 

 more than the other minerals are granulated. In structure the rock 

 ranges from only faintly gneissoid to very clearly gneissoid, which 

 is due to the arrangement of the dark colored minerals with axes 

 parallel to the direction of foliation. All facies of the syenite are 

 quartzose and the range in mineral composition is from pyroxene- 

 quartz-syenite to granitic hornblende syenite as shown in table i.^ 



1 In this and the succeeding tables only close approximation to the volu- 

 metric proportions of minerals present is intended. 



