GEOL OGY OF MONA DNO CK MO UNTA IN 1 1 



the strike, or direction of joint 2, varies from 40° to 90°, but in 

 five cases out of the nine is between 50° and 65°. 



3. The angle between the true dip and the dip of the surface of 

 joint I in five, out of seven, cases approximates to a right angle. 



The meaning of observations i and 3 is that this schist has 

 been broken perpendicularly to the laminae into strips from one 

 end of the syncline around to the other ; and observation 2 

 shows that these strips have been broken crosswise, less regularly, 

 into shorter pieces or blocks, the latter indicating a bending or 

 twisting in these strips. There is, I think, no doubt but that 

 these joints were produced by the bending of the schist into the 

 great synclinal fold of the mountain, and this, as has been 

 pointed out, accompanied the intrusion of the granite. The 

 formation of the joints in this schist clearly indicates that this 

 rock was in the zone of fracture when this intrusion and folding 

 took place. The same is indicated by the brecciation appearing 

 in some of the schist fragments included in the granite. 



But there is another and earlier folding evident in this schist. 

 The accompanying illustration shows a compressed, overturned 

 anticline occurring near the top, on the west side, which is con- 

 spicuous for a distance of several hundred feet down the moun- 

 tain to one ascending on that side. The part of the fold 

 appearing in the picture is 37 feet long by 6 wide, and the apex 

 of the fold as seen in this section points between northwest and 

 north. This means that the fold is overturned and lies flat in 

 the western side of the large syncline, with the apex of this 

 small anticline pointing away from the apex of the large syncline. 

 The formation of this small anticline, though the bending was 

 so severe, was not accompanied by fracture, as may be seen in 

 the illustration (Fig. 5). Other folds, though less conspicuous, 

 may be seen of which the same is true, and the jointing of the 

 schist cuts through these, indicating utter independence of the 

 one of the other. Therefore, when these smaller folds were 

 made the rock was in the zone of rock flowage. There are 

 indicated, therefore, two periods of metamorphism — one at a 

 greater depth when the clastic was recrystallized and in places 

 severely folded without fracture ; and the other at less depth 



