NOTES ON A GRANITE CONTACT ZONE. M C INTOSH. 249 



extends into the slate. This doubtless resulted from the 

 absorption of some of the slaty material, although no further 

 evidence of such was found. 



There is no evidence of any gases or vapours from the 

 molten granite having been a factor in the alteration of the 

 slate of the area studied. 



Something like the following would be a sequence of 

 events for this area. In Pre-Cambrian time, fine sediment 

 containing a good deal of carbonaceous material was deposited 

 in the water some distance off shore, on a slowly subsiding 

 sea-bottom. This became consolidated into a carbonaceous 

 shale. Pressure set in from the direction of the Atlantic 

 seaboard, and continuing through long periods of time threw 

 the great thickness of rock into high folds. The pressure 

 converted the shale into a slate. Then in Devonian time came 

 the intrusion of the granite, the heat from which changed the 

 slate within the sphere of its influence into a cordierite-slate^ 

 and near the contact, where the alteration was greatest, into 

 an andalusite-cordierite slate. During parts of the long 

 periods that have elapsed since then, as well as in previous 

 periods, erosion processes have been at work, resulting in the 

 present day aspect of the area. 



