THE LAUR ENTIA N PENEPLA IN 643 



On the western arm of the peneplain the uplanji still 

 presents the same general features. The head-waters of all the 

 rivers flowing- to James Bay, where they flow over Archaean 

 rocks, alternate between long lake-like expansions with little 

 current, and short, contracted portions characterized by rapids 

 and falls. Where they cross the ancient or modern coastal plains 

 the fall is uniform, and usually, except at times of high water, 

 they present an almost unbroken succession of small shallow 

 rapids full of bowlders and gravel bars. (See Low, 23, p. 18.) 



Tyrrell draws attention to the fact that 



A particularly noticeable feature of the "Barren Lands" is the absence of 

 valleys for the rivers. The Telzoa River probably the largest stream in all 

 that country, is, through the greater part of its course from Daly Lake to 

 the head of Chesterfield Inlet, merely a succession of lakes of larger or 

 smaller size lying in original depressions in the till or rock, connected by 

 stretches of rapid water flowing in one or more shallow, tortuous and often 

 ill-defined channels frequently chocked with boulders. (33, p. 395.) 



The deep, steep-sided gorges cut below the level of the plain 

 are less in evidence on its western part. Shallower gorges occur, 

 but generally only for short stretches along the rivers. There 

 are, however, a number of broadly open valleys, more or less 

 occupied by sediments, which have been provisionally classed as 

 Cambrian. Tyrrell states 



It would seem probable that the drainage has alwa5'S followed the main 

 valleys which still trench the surface, running more or less at right angles to 

 the mountains. The pre-Cambrian valley of Chesterfield Inlet, extending 

 eastward towards Hudson Strait, and westward towards Great Slave Lake, 

 and the post-Cretaceous valley of the Saskatchewan, extending towards the 

 lower valley of the lower Nelson River, and many other valleys running more 

 or less parallel to these, go to prove the general correctness of this statement. 

 (35, p. I49-) 



The partial re-excavation of some of these depressions, occu- 

 pied at least in part, by early Paleozoic sediments has given rise 

 to the eastern extension of the basins of Lake Athabasca, Great 

 Slave Lake, and Great Bear Lake. Reference has already been 

 made to the valley of Chesterfield Inlet, and it is not improbable 

 that Wager River (or Inlet) north of this owes its origin to a 

 similar cause. 



