460 NEW YORK STATE MUSEUM 



end of Lake Catlin in the extreme southeast part of the quadrangle. 

 This is likely a northward spur of the great Grenville belt which 

 Kemp has mapped as running east for miles along the Long Lake- 

 Newcomb road, in the Newcomb quadrangle which corners the 

 Long Lake quadrangle on the southeast. At the time Kemp's 

 map was made only the actual limestones and closely associated 

 schists were being included in the Grenville, whereas these rocks 

 are quartz gneisses. 1 



On the Tupper Lake quadrangle, next west of the Long Lake, 

 there is again at least one great belt of Grenville rocks, as yet 

 unmapped, for numerous exposures of these rocks appear for 

 several miles along that part of the Long Lake-Long Lake West 

 road which lies between Little Tupper lake and the railroad. 



In addition to these belts there are several patches of varying 

 extent of Grenville rocks occurring within the quadrangle limits, 

 and such as have been recognized are indicated upon the accom- 

 panying map. 



As usual, most of the Grenville country is valley country, owing 

 to the weakness of these rocks as compared with the other crystal- 

 lines. In general the outcrops are infrequent, scattered and 

 poorly exposed, so that little or nothing can be done toward de- 

 ciphering the stratigraphy, or the structure. It is certain that the 

 rocks are considerably folded, and also that the folds pitch, causing 

 frequent changes in the direction of strike. The quartz gneisses 

 form an exception to the general rule. Where present in consider- 

 able thickness, as they are about the lower end of Lake Catlin, 

 they constitute respectable hills, several hundred feet in hight, 

 on the sides of which exposures abound. 



These quartz gneisses, or schists, constitute a prominent feature 

 in the Grenville series of the quadrangle. They are metamorphosed 

 sandstones of varying degrees of purity, and occur in part in beds of 

 large thickness and fairly uniform character, and in part in com- 

 paratively thin beds, alternating with beds of mica gneiss and of 

 impure limestone. These latter quartz schists are much more 

 variable in character than are the thick ones. In general the rock 

 is rather evenly granular, though there are all gradations between 

 a sugary, granular, weak rock, and hard, solid, glassy quartzites. 

 In many instances thin layers of coarse, solid quartz alternate 

 with the granular layers, and may comprise upward of half the 



iN. Y. State Geol. 17th An. Rep't. Map opposite p. 550. 



