SECTIONS IN BOW RIVER VALLEY. 55 



silts and it thus passes up gradually into the next member of the section, 

 which forms nearly the entire upper part of the bank. The silts over- 

 lying the boulder-clay are yellowish gray in color, well bedded and fre- 

 quently show minute cross-bedding between the more prominent hori- 

 zontal planes. They vary a little in tint and fineness and sometimes 

 include layers two or three inches thick, of brownish color and leathery 

 texture, composed of almost paper-like leaves. Glaciated stones, some- 

 times large, occur here and there throughout the silts, and they also 

 include at this place one or more la3^ers of a few feet thick which are 

 markedly stony, not very distinctly stratified and differ in no material re- 

 spect from the boulder-clay except that they are somewhat less coherent. 

 Laurentian fragments become increasingly frequent toward the top of 

 the silts, but are never abundant at this place.* 



Above the bridge and about a mile distant another bank shows these 

 silty deposits resting directly on the lower gravels without any boulder- 

 clav. 



It is here quite clear that the boulder-clay and silts represent a single 

 deposit which took place under varying conditions and in which the 

 boulder-clay forms, broadly speaking, lenticular masses, not persistent 

 and not characteristic of any particular horizon or coextensive with the 

 region of deposit. The section is as a whole, moreover, that of a series of 

 stratified deposits, in which evidences of tumultuous deposit and obscure 

 bedding occur only in the case of the boulder-clay and the underlying 

 gravels. t 



Beyond Calgary, Mr McConnell writes as follows of the sections along 

 the river : 



" Four miles above Calgary the glacial deposits consist in descending 

 order of 3 feet of gravel and soil, 8 feet silt, 2 feet boulder-clay, 1^ feet 

 silt and 20 feet of gravelly boulder-clay. No eastern pebbles are found 

 in this section, nor were any found in the valley of the Bow west of Cal- 

 gary, notwithstanding the fact that three miles to the northwest boulders 

 of Laurentian origin occur on the summit of the Nose hills at an eleva- 

 tion of 550 feet above the river at this point (3,934 feet above sealevel).^ 



*The boulder-clay in this section is evidently either the "lower" or "upper" boulder-clay of 

 the plains. Boulder-clay holding eastern stones is here recognized for the last time in approach- 

 ing the mountains by the Bow valley. 



t It may here be noted that a section identical in character with that at Calgary has since been 

 examined at Edmonton, on the Saskatchewan, abont 200 miles north, nearly in the same longitude 

 and at an elevation of about 2,200 feet. The Saskatchewan gravels, sparingly developed, are here 

 covered by 50 feet or more of alternating boulder-clay and well stratified silts. The boulder-clay 

 occurs in layers of two, three or more feet in thickness. Most of the stones are included in it, and 

 there are Laurentian and western in proportions respectively of about 1 to 2. 



X Faintly impressed terraces, like those of the Porcupines, occur at several levels upon the 

 eastern slope of this plateau, the best marked at a height of about 3,900 feet. 



VIII— Bull. Geol. Soc. Am., Vol. 7, 1895. 



