GEOLOGY OF THE LONG LAKE QUADRANGLE 463 



the strike. South from Follensby pond the rocks are much folded 

 and with a general northwest strike, and south dip, but with much 

 variation in both. This is in sharp contrast with the prevailing and 

 usually high south dips in the Rock pond belt. The high dips 

 occasionally run up to vertically and become steep north, sug- 

 gesting the truncated tops of closed folds, but the north dip never 

 persists very far. The Follensby Grenville is plainly cut out along 

 the strike by the syenites which lie to the west, as would be expected 

 from their proved intrusive character and later date. 



Along Cold river the strike varies from n. 25 w. to n. 50 w. in 

 the few exposures, with a general dip of 45 s., though with much 

 variation and plainly much folding. This strike is very suggestive 

 of the extension of this belt to the northwest to a connection with 

 the Moose creek belt, the proof of which can not be furnished owing 

 to lack of exposures. 



About Lake Catlin the strike varies from n. 8o° w. to n. 6o° w. 

 and the dip is again to the south, and usually under 25 . West of 

 the lake the sediments are much involved with gneisses apparently 

 igneous, which soon cut them out entirely. On the hill in the 

 extreme southeast corner of the quadrangle there is a thickness of 

 close to 500 feet of the quartz gneiss exposed. 



No order of rock succession involving the different members of 

 the Grenville could be made out anywhere, and but the vaguest 

 ideas concerning the thickness could be obtained. In addition to 

 the quartz gneiss thickness just quoted, a thickness of at least 200 

 feet of quartz pyroxene gneiss and impure limestone is shown on 

 the low hill just south of Rock pond. But these are mere local 

 details of what is certainly a great and thick rock series. 



Doubtful gneisses. These rocks divide themselves into two main 

 groups: in the one we find comparatively uniform igneous gneisses 

 without sedimentary admixture; in the other frequent bands or 

 patches of Grenville rocks, and also frequent rocks of doubtful 

 nature but with a Grenville look, appear associated with the igneous 

 gneisses. The first group will be styled for convenience the " Long 

 lake gneiss " and the second " the Grampus gneiss." The edge 

 of another great mass of these rocks appears in the extreme north- 

 west part of the quadrangle, and extends widely westward. This 

 will be called the " Piercefield gneiss." 



Long lake gneiss. This occupies a large area in the southern 

 half of the quadrangle on both sides of Long lake, constituting the 



