12 NEW YORK STATE MUSEUM 



also prominent in the areas of mixed gneisses below described but 

 it is there too intimately associated with the other rocks to admit 

 of separate mapping. Even in the areas actually mapped as Gren- 

 ville the rock is not always pure because at times small masses of 

 igneous rocks are intimately associated. In such cases the writer 

 has mapped as Grenville all areas where the sediments greatly pre- 

 ponderate. On the adjoining Saratoga sheet the Grenville is also 

 extensive so that it is much more prominent along the southeastern 

 than the southwestern border of the Adirondacks. 



As shown on the accompanying geologic map the Batchellerville- 

 Barkersville area is the largest within the quadrangle. A strike of 

 from north 30 to 50 east with southerly dip of from 30 to 6o° 

 is very common over all the area except the northeast por- 

 tion where the strike is north 8o° east with dip 20 south 

 and the extreme south where the strike is north 8o° east with dip 

 nearly vertical. Nearly all the varieties above described are to be 

 found, the feldspar-quartz-biotite-garnet gneisses being by far the 

 most common. As already stated, limestone has been observed at 

 but one locality and such a small amount in this large Grenville 

 mass is not a little surprising. Quartzites, which must have been 

 derived from very pure sandstones, are quite common and three 

 fairly well-defined belts are especially noteworthy [see map] . One 

 of these belts, about a mile long and a third of a mile wide, lies 

 just to the northeast of Batchellerville. Much of the quartzite is 

 very pure and in thin to thick beds with strike north 30 ° west, dip 

 30 south and apparently showing a thickness of hundreds 

 of feet. The second quartzite belt, about two miles long and one- 

 half mile wide, lies southeast of Fox Hill. The rock is thin-bedded 

 and much like a quartz schist with frequent thin layers of mica. It 

 strikes mostly north 70 ° west dip 20 south. A third belt 

 comprises all of the Grenville tongue just north of North Galway. 

 It is a very pure quartzite and the beds, which stand nearly vertical, 

 strike north 8o° east. The four inliers 1 in the vicinity of North 

 Galway are also of quartzite. Throughout this great area the Gren- 

 ville is unusually pure and free from closely involved igneous in- 

 trusions except around Johnnycake lake and in the region to the 

 east of Parkersville, but even in these cases the sediments greatly 

 preponderate. 



In the area northeast of Northville no limestone and little or no 

 quartzite has been noted. Frequently granitic and syenitic rocks 



1 The term " inlier " is here used as defined in Scott's Geology, 2d edi- 

 tion, p. 384. 



