192 



Tlie Philippine Journal of Science 



1915 



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desites and dacites, are encountered 

 but east of Bontoc the formation 

 becomes very shortly diorite and 

 granite. This belt of granitic rocks 

 is only from 8 to 10 kilometers 

 wide. There is more andesite, or 

 rather a ver>' fine-grained, almost 

 aphanitic phase of diorite, succeed- 

 ing the granite on the east as far 

 as the town of Barlig, where 

 steeply dipping sandy shales are 

 encountered. These incline to the 

 southeast. 



Sandstone makes up the main 

 mass of Mount Amuyao, and from 

 there east to Cagayan Valley sedi- 

 ments occur. In places, as at 

 Natonin, there are small areas of 

 extrusive rocks overlying the Ter- 

 tiary sediments. No limestone was 

 seen east of Barlig, but farther 

 north on the crest of the range 

 east of Tinglayan I could detect 

 limestone cliffs with the aid of a 

 binocular. They are nearly 2,200 

 meters in elevation. 



The apparent structure of the 

 sediments in the eastern part of 

 the section is indicated in the dia- 

 gram. 



THE PLUTONIC ROCKS 



The Plutonic rocks consist of 

 granite and diorite. 



The granite. — This formation 

 was found at two points, a short 

 distance east of Bontoc and in the 

 Saltan Valley. It appears to be a 

 long intrusive mass, whose axis 

 runs from northwest to southeast. 

 It is a typical quartz-feldspar-bio- 

 tite granite and has a grayish to 

 glaring white appearance in the 



