166 



THE GEOLOGY OF THE CANOBOLAS MOUNTAINS, 



alkaline in composition. This gives these rocks a darker colour, 

 some of them appearing andesitic or even basaltic in appearance 

 in the hand-specimen. These characteristics make the mapping 

 of the boundaries between this series and the more basic rocks 

 somewhat uncertain; and, in many places, the boundaries gi\ en 





VERTICAL SCALE r- 



300 FEET ' 



Fig. 1. — Diagrammatic Section from Towac Mountain to Tiae Devil's Hole, 

 showing succession of lavas and tutt's. 



in the accompanying map are only approximate. The alkaline 

 trachytes outcrop over a considerably larger area than do the 

 more acid type. They are found capping the comendites of tlie 



