2 
MUSEUM BULLETIN NO. 21. 
whole Palaeozoic belt from 50 to 100 miles north and west of the 
sections described in my last summary report. 1 
TOPOGRAPHY AND DRAINAGE. 
The topographic features of northern Manitoba are the 
product of a series of degradational factors which have been 
successively dominant in moulding the relief of the region. The 
present topography is the joint product of a long period of pre- 
glacial erosion, succeeded by the work of the great ice sheet, 
which in turn has been modified by extensive deposition of 
lacustrine and fluvial sediments. The position and relative 
height of the larger features of relief were determined by a long 
cycle of erosion preceding the glacial epoch. During this early 
stage of topographic development the dip and strike and relative 
hardness of the several rock formations were the chief controlling 
elements in directing the maximum effects of erosion. Under 
the influence of a gentle westerly dip the edges of the different 
groups of strata retreated westward at different rates. The 
northwesterly and southwesterly trending scarps which were 
developed at this period correspond in direction with the general 
direction of the strike of the rocks. 
By far the most conspicuous and important topographic 
feature developed at this time is the Cretaceous escarpment 
marking the eastern front of an elevated plateau known from 
south to north under the several names of Duck mountain, 
Porcupine mountain, and Pasquia hills. The eastern face of this 
escarpment rises sometimes abruptly but more often by a series 
of foothills and terraces to a height of nearly a thousand feet 
above the broad plain occupied to the east and north by the 
basins of Lake Winnipeg, Winnipegosis, Cedar, and many smaller 
lakes connected with the lower valley of the Saskatchewan river. 
Another, but less conspicuous, escarpment separates the Win- 
nipeg basin from that of the other two lakes mentioned above. 
This scarp marks the eastern limit of the Silurian limestone. 
It is well developed in the north and rises somewhat more than 
100 feet above Lake Winnipeg in the vicinity of the Saskatche- 
1 Sum. Rept., Geo!. Surv. Br., Dept, of Mines, for 1912, pp, 404*406. 
