CONTACT OF ARC H^ AN AND POST-ARCHMAN 4 I 



As before, the Archaean hills rise several hundred feet above the 

 waters of the lake, and the post-Archaean sediments abut against 

 them at the water's edge. 



The general direction of the shore line from Sault Ste. Marie 

 to Michipicoten is i 5 ° W. of N. It is, however, not so regular as 

 other parts of the coast. At Gross Cap, Mamainse and Gargan- 

 tua the Archaean projects to the west in three sharp teeth with 

 deep bays between. At each point there occurs a small area of 

 Keweenawan rocks lying almost flat and rising but little above 

 the waters of the lake. The Archaean hills rise, on the contrary, 

 almost vertically for several hundred feet, and at a few miles 

 from the shore reach as much as 1,200 feet. The line of disloca- 

 tion in this region is not straight, but serrate. The general 

 direction of all the north-bearing lines is, however, preserved. 



From Michipicoten the shore line trends due west, rising in 

 steep, precipitous hills. No post-Archaean sediments are found 

 in contact with the Archaean, but Michipicoten Island of Kewee- 

 nawan age is only a few miles south. 



From the mouth of the Pucaswa River the shore line bears 

 about 18° W. of N., having the same high, precipitous Archaean 

 cliffs, and with no post-Archaen sediments above water level. 



From Heron Bay the shore line again bears about 10° N. of 

 W. as far as Nipigon Bay. Archaean hills rise perpendicularly 

 several hundred feet above the lake. In Nipigon Bay Keewee- 

 nawan sediments appear, with interbedded lava sheets, the whole 

 rising several hundred feet above the level of Superior. 



The contact here turns again to the north, but on the map 

 does not appear to be so definite. The Archaean hills do not 

 rise in vertical cliffs along the eastern shore of Lake Nipigoan, 

 and in consequence the lava flows of the Keweenawan, having no 

 definite walls to impinge against, spread out in irregular bays. 

 The east shore of Lake Nipigon is prolonged into a deep, narrow 

 bay at the south, and from this a valley leads through to Lake 

 Superior, which is believed by Parks to be an old outlet of the 

 lake. This valley and bay are in direct line with the east shore 

 of Lake Nipigon and are taken to represent the counterpart of 

 the coast lines described in earlier paragraphs. The Archaean to 



