Mesozoic and Ctenozoic Geology and Palceontology. 321 



The drift deposits cover the second prairie plateau west of the Red 

 river and Turtle mountain, and the eastern front of Pembina escarp- 

 ment is distinctly terraced and the summit of the plateau thickly cov- 

 ered with drift. The first terrace is about 50 feet above the general 

 prairie level, the second about 260 feet, and the third about 360 feet. 



One hundred and twenty miles west of Turtle mountain, the second 

 prairie plateau comes to an end against the foot of the great belt of 

 drift deposits, known as the Missouri Coteau, a tumultuously hilly 

 country, based on a great thickness of drift. The Missouri Coteau is 

 a mass of debris and traveled blocks, with an average breadth of 30 

 to 40 miles, extending diagonall}' across the central region of the con- 

 tinent with a length of 800 miles. It appears to have been the work 

 of sea-borne icebergs, and not glacier ice as such. 



In 1876, Mr. Robert Bell* said, that in the prairie regions of the 

 northwest territory, loose deposits of Post-Tertiary age cover the sur- 

 face of the country almost universally, and they are usually of con- 

 siderable depth. There are immense areas having the same general 

 elevation, or without very great or sudden changes of level, yet, with 

 the exception of the first prairie steppe, there is a remarkable scarcity, 

 or perhaps absence, of extensive stratified deposits of sands and clays, 

 such as occur in the provinces of Ontario and Quebec. The bulk of 

 the superficial deposits is of the nature of bowlder-clay or unmodified 

 drift, which is spread alike over the older rocks from the lowest to the 

 highest levels. The materials of the drift appear to be made up of 

 the debris of the rocks existing in situ, immediately beneath or a short 

 distance to the northeastward, together with a greater or less propor- 

 tion derived from those lying further off" in the same direction. As a 

 rule, the softer or more clayey part has come from the underlying- 

 strata, while the harder pebbles and bowlders are the furthest trans- 

 ported; still, in washing out the finer ingredients, it is always found 

 that much of the incorporated sand and gravel is of foreign origin. 

 The nature of the transported bowlders and pebbles varies in different 

 localities, but more than half of its bulk, on an average, consists of 

 local material. On the first and second prairie steppes the most abun- 

 dant constituent of the transported portion is Laurentian gneiss, while 

 the remainder is made up of light-colored unfossiliferous limestones, 

 supposed to be Silurian and Devonian, together with a proportion of 

 Huronian schists, which varies in diff"erent localities. On the third 

 steppe, however, smooth pebbles of finely granular quartzite predomi- 



* Geo. Sur. of Canada, for 1874-75. 



