152 



Manitoba and Saskatchewan. The total area covered 

 by the lake during the various stages of its existence has 

 been estimated to have been not less than 110,000 square 

 miles (275,000 sq. km.). The deposits laid down in the 

 deeper parts of the lake consist of a thin layer of clayey 

 silt but along the shore, gravel and sand were built up to 

 a thickness of — in some of the deltas — 50 to 200 feet 

 (15 to 60 m.) [20; 21]. 



The post-glacial deposits around Lake Nipigon 

 were laid down in Lake Warren, the largest of the lakes 

 which occupied the upper part of the St. Lawrence basin 

 following the retreat of the Labradorean ice sheet. A 

 northern bay of this lake covered a wide area of country in 

 the vicinity of Lake Nipigon. The deposits from this bay of 

 Lake Warren are found along the railway between Wagam- 

 ing and Ombabika bay, a distance of 30 miles (48 km.). 

 They consist of stratified sand underlain by clay and have a 

 thickness of approximately 100 feet (30 m.) (6) (14) (22). 



The third area of lacustrine deposits traversed by the 

 railway, were laid down from a lake which lay for the most 

 part in the southern part of the James Bay basin but also 

 extended across the St. Lawrence-Hudson Bay divide 

 into the Ottawa basin, for, in northwestern Quebec, the 

 lacustrine clays have been traced continuously from Lake 

 Timiskaming to points north of the divide. For this body 

 of water the name Lake Ojibway has been suggested by 

 A. P. Coleman. The areal extent of its deposits have not 

 yet been precisely ascertained but they are known to occur 

 throughout an area of at least 50,000 squaie miles 

 (125,000 sq. km.). They occur almost continuously along 

 the National Transcontinental railway from the crossing of 

 the Kenogami river to Cochrane a distance of 320 miles 

 (515 km.), and to the eastward of Cochrane for a distance 

 of 210 miles (350 km.), — a total extent from east to west 

 along the railway of 530 miles (853 km) (9). They 

 consist largely of uniformily stratified clays or clay and 

 sand and for that reason the region throughout which they 

 occur is known generally as the "clay belt." Their thick- 

 ness is nowhere very great the maximum recorded in the 

 cuts along the National Transcontinental railway being only 

 26 feet (7-9 m.). [1, 2, 3, 5, 10, 11, 13, 26, 27]. 



