32 Forestry Quarterly 



to the contact with the Archean rocks. These undisturbed sedi- 

 ments have produced a generally flat and level type of country, 

 rising gradually towards the west. The region is relieved, how- 

 ever, by occasional low residual elevations originating from pre- 

 glacial circum-denudation. These hills, or mountains as they 

 are sometimes called, generally rise less than 1,000 feet above 

 the surrounding country and are composed of shales and sand- 

 stones of upper cretaceous age. The more prominent of these 

 elevations occur along the line of the Manitoba escarpment, which 

 marks the boundary between the first and second prairie levels, 

 and also in northern Alberta. They are all heavily mantled with 

 glacial drift and few outcrops of bed rock can be noted. 



The greater portion of the region is covered with drift and as a 

 result a rolling type of country has been produced. Well-defined 

 eskers and kames are frequently noted, but it is the familiar low, 

 rounded ridges of boulder clay which are most characteristic of 

 the region. 



A third prominent feature is the large areas of lacustrine strati- 

 fied clays which have originated from pre-glacial and post-glacial 

 lakes that at one time were very extensive in this country. These 

 areas possess an extremely flat and level appearance and are 

 usually poorly drained. The most important and characteristic of 

 the lascustrine plains is that of Lake Agassiz, which covered 

 several thousand square miles and of which the Winnipeg system 

 of lakes is the residue. Extensions of Lake Athabaska in north- 

 ern Alberta have also given rise to large areas of this nature. 



Occasionally extensive delta deposits of sands are encountered. 

 Of this nature are the sand lands forming the Nisbet and Fort 

 a la Conne Forest Reserves east of Prince Albert, Saskatchewan. 

 They were formed in Lake Agassiz and its western extension, 

 Lake Saskatchewan, by the Saskatchewan River. 



The majority of the lakes of the region merely occupy shallow 

 depressions in the drift and clay deposits and bear no relation to 

 the pre-glacial features of the country. 



In the western portion of the region the larger rivers have cut 

 rather deep well-defined valleys, but the tributaries are generally 

 sluggish. 



Based on soil, moisture and topography, three permanent types 

 can be distinguished. These are as follows: The boulder clay 

 slopes type ; the sand ridge type ; the swamp muskeg type. 



