PRE-CAMBRIAN OF NORTHERN ONTARIO AND QUEBEC 319 



south part of Boston Township there is a similar band, the upper 

 side of which was determined by similar means to be the south. 

 The bands are of about the same width, the southern one somewhat 

 the wider, as it contains a larger proportion of interstratified basalt 

 flows which could not be separated in mapping. There can be no 



\777\ E 



Fig. 5. — Sketch map showing the tuff bands in Boston and Otto townships and 

 their relations to the Timiskaming series. 



doubt therefore that the two bands form the Hmbs of an anticline 

 whose crest has been cut off by erosion. The dips of the strata in 

 both bands average about 70 degrees or higher. At their nearest 

 point of approach the bands are about 17,000 feet apart, so that 

 the axis of the anticline may be considered to be approximately 

 8,500 feet from the base of each band. 



The syenite batholith to the north of the tuffs in Boston Town- 

 ship prevents the calculation there of the thickness of the Keewatin 



