But we ought to take a nearer view of these wonderful conditions. A convenient point of approach will be just east of Banff, Alberta, near Kananaskis Station, where the Fairholme Mountain has been described by R.G. McConnell of the Canadian Survey. The latter remarks with amazement on the perfectly natural appearance of these Algonkian limestones resting in seeming conformability on Cretaceous shales, and says that the line of separation between them, called in the theory the “thrust plane,” resembles in all respects an ordinary stratification plane. I quote his language:
“The angle of inclination of its plane to the horizon is very low, and in consequence of this its outcrop follows a very sinuous line along the base of the mountains, and acts exactly like the line of contact of two nearly horizontal formations.
“The best places for examining this fault are at the gaps of the Bow and of the south fork of Ghost River.... The fault plane here is nearly horizontal, and the two formations, viewed from the valley, appear to succeed one another conformably."
[Footnote 48: Annual Report, 1886, Part D, pp. 33, 34.]
This author adds the further interesting detail that the underlying Cretaceous shales are “very soft,” and “have suffered very little by the sliding of the limestone over them."
About a hundred miles further south, but still in Alberta, we have the well-known Crow’s Nest Mountain, a lone peak, which consists of these same Algonkian limestones resting on a Cretaceous valley “in a nearly horizontal attitude,” as G.M. Dawson says, which “in its structure and general appearance much resembles Chief Mountain," another detached peak some fifty miles further south, just across the boundary line in Montana.
Chief Mountain has been well described by Bailey Willis, who estimates that the Cretaceous beds underneath this mountain must be 3,500 feet thick; while the so-called “thrust plane is essentially parallel to the bedding” of the upper series.
“This apparently is true not only of the segments of thrust surface beneath eastern Flattop, Yellow, and Chief Mountain, but also of the more deeply buried portions which appear to dip with the Algonkian strata into the syncline. While observation is not complete, it may be assumed on a basis of fact that thrust surfaces and bedding are nearly parallel over extensive areas."
[Footnote 49: Report, 1886, Part D, p. 84.]
[Footnote 50: Report, 1885, Part B, p. 67.]
[Footnote 51: Bull. Geol. Soc., Vol. 13, pp. 305-352.]
[Footnote 52: Id., p. 336.]
[Footnote 53: Id., p. 336.]