40 G. M. DAWSON — GLACIAL DEPOSITS OP SOUTHWESTERN ALBERTA. 



" greenstone," about which some remarks are made subsequently. One 

 or two pebbles of peculiar crystalline rocks, not Laurentian, and prob- 

 ably from intrusive masses in the mountains, were also found. 



The Saskatchewan gravels are sharply cut off above by a dark boulder- 

 cla}'', the color of which is evidently due to the incorporation of a consid- 

 erable proportion of the material of the Pierre shales and in wliich rather 

 numerous crumbs of the coal of the vicinity are contained. The included 

 stones are varied in origin, embracing quartzites from the mountains, 

 Laurentian gneisses and some limestone of mountain origin, all often 

 distinctly striated and glaciated. 'The thickness of this boulder-clay is 

 about 50 feet. 



Next in ascending order is a tliickness, from 25 to 30 feet, of pale 

 colored silty beds, often very finely stratified and in certain layers assum- 

 ing a '• leathery " character and showing layers of almost 2^ai)er-like fine- 

 ness. Crumbs of coal are present, but no lignite or peaty layer is here 

 seen. This well bedded intercalation preserves its place and character 

 for miles along the valley and is continuous with that previously de- 

 scribed lower down the river.* 



Overlying the last is the " upper " boulder-clay, 3'ellowish gray in color, 

 and this, so far as can be ascertained, extends n earl 3' or quite to the top 

 of the bank or the general level of the adjacent prairie. Stones and 

 boulders are not notably abundant in it at this place, l)ut those wliich 

 occur came both from the mountains on the west and the Laurentian 

 plateau on the east. 



Summarizing tliis section and placing it in relation to others described 

 in the report of 1882-'84, we obtain the following rei)resentation of the 

 drift deposits of this part of the plains, the section on the right being that 

 farthest from the base of the mountains : 



Sections on Belly River. 



Near Lethbridge. 



Driftwood bend. 



Wolf island. 



Distance from mountains, 60 

 miles. 



Heiglit of base of section, 2,G55 

 feet. 



Distance from mountains, 75 

 miles. 



Height of base of section (ap- 

 pro.ximate), 2,3G0 feet. 



Distance from mountains, 85 

 miles. 



Heiglit of base of section (ap- 

 pro .Ki mate), 2,270 feet. 



Feet. 

 Upper boulder-clay (about)., 140 



Interglacial deposits 30 



Lower boulder-clay 50 



Saskatchewan gravels 15 



Pierre (Cretaceous) shales.. 65 



300 



Feet. 

 40 



Feet. 

 100 



(Sands, ironstone, carbon- 

 aceous layers) 33 



80 



(Sandy clay, with lignite)... 8 

 15 



(Below river level.) 



153 



(Gravels, sands and clay).... 40 



(Cretaceous rocks) 10 



173 



Report of Progi'ess, Geol. Survey of Canada, 18S2-'8I, p. 144 C. 



