56 G. M. DAWSON — GLACIAL DEPOSITS OF SOUTHWESTERN ALBERTA. 



" Eight miles above Calgary a section showing the following sequence 

 was examined : 



Feet. 



1 . Soil and silts 15 



2. Clay with layers of silt 10 



3. Gravellj' sands 5 



4. Stratified sands 4 



5. Gravelly boulder-clay 6 



6. Yellowish sands 40 



80 



" The cla}^ (number 2) underlying the upper silts is peculiar and was 

 not observed farther east. It is destitute of stratification, light blue in 

 color on a fresh surface, very compact and highly calcareous. It prob- 

 ably represents the fine material produced by glacier erosion, sorted from 

 the coarse products, and carried eastward by glacial streams until the 

 lessening current or a lake basin allowed its deposition. The silts over- 

 lying it have the characters of a lake deposit. 



" Four miles below Cochrane (30 miles from the mountains) a section 

 shows the same glacial clay referred to above, resting on boulder-clay and 

 overlain by silts. The boulder-clay along this part of the river ranges in 

 thickness from 20 to 40 feet and consists of a light drab colored sandy 

 clay filled with striated and rounded peb])les and l)oulders of limestone 

 and quartzite. It is separated in places from the overlying fine clay by 

 sandy and gravelly beds, but in others merges gradually into it. The 

 fine clay, like the boulder-clay, is variable in thickness, ranging from 15 

 to 50 feet. It holds a few scattered pebbles, which are often glaciated, 

 and are occasionally found in an upright position and at various angles 

 to the plane of the deposit — a fact probably due to their having been 

 dropped from floating ice. The silts have a thickness here of about 100 

 feet. They exhibit curved cross-bedding, resembling the kind known as 

 flow-and-plunge structure, except that the curved layers are short, seldom 

 exceeding six inches in length, and the surfaces are concave upward. 

 Pebbles, some of which are striated, occur tliroughout the section and 

 lumps of clay are found at intervals. 



" Opposite Cochrane the boulder-clay has a thickness of 125 feet. At 

 the mouth of the Jumping Pound, three miles farther up, it is much 

 thinner, and is overlain by flood-plain gravels. Half a mile l^elow Ghost 

 river the boulder-clay is overlain by 40 feet of coarse sands and gravels, 

 above which is 20 feet of river wash. 



" From this point to the mountains, a distance of about 20 miles, the 

 boulder-clay has been washed away in most places and the older rocks 

 are covered directly with river gravels. Small sections, however, occur 

 at Morley, 15 miles east of the mountains, near the mouth of a creek 



