238 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



This formation is, in general, a lithological unit, being composed essentially 

 of limestone, massive and thin-bedded, with intercalated layers of calcareous 

 shale. The shaly character of the beds is more evident towards the base of 

 the formation. On a fresh surface the rock composing the whole band is 

 characterized by its grey or bluish colour, while on weathered faces it is 

 light grey to black. The shale bands are so distributed between the more 

 massive beds that they do not greatly affect the steepness of the slope on the 

 exposed face. 



At various horizons in the formation, the beds consist of alternating bands 

 from i inch to 2 inches thick, of varying hardness, so that on the weathered 

 surface the rock has a distinctly furrowed appearance. Although in such cases 

 the fresh surface of the rock may appear to be uniform in composition, yet in 

 reality the harder bands are dolomitic or siliceous, while the softer bands are 

 calcareous. Cherty layers are very common in this formation ; they usually 

 are less than i inch thick, but their greater hardness causes them to form 

 ridges on the weathered surfaces. This banded or furrowed character is well 

 exposed in the limestone on the east slope of Garnet mountain. 



At Wolverine Pass (see pis. 75, 76), high cliffs of thin layers of 

 bluish-gray limestones are finely exposed and readily accessible. It 

 was here that Mrs. Walcott and I collected a few characteristic Upper 

 Cambrian fossils. 



Thickness. — Allan measured a partial section on the east side of Ice 

 River Valley that has a thickness of 1,550 feet (472.4 m.) and a 

 more complete section on the south slope of Ottertail Valley, where 

 the total thickness of the formation is 1,640 feet (499.9 m.). There 

 is an apparent rapid thickening of the Ottertail to the southeast, 

 where, on Limestone Peak Allan estimated a thickness of 2,450 feet 

 (746.8 m.) of limestone.' It is possible, however, that the upper por- 

 tion of this inaccessible section may be formed of the siliceous lime- 

 stone and shale of the superjacent Goodsir formation. 



Geographic distribution. — The Ottertail, like the overlying Goodsir 

 and subjacent Chancellor formation, is, as far as known, narrowly 

 limited in its east and west distribution to the Ottertail and Vermilion 

 Ranges southeast of the Kicking Horse River, although it probably 

 continues southeast into the Mitchell Range between the Kootenay 

 River and the Continental Divide. I noted, a little north of Cross 

 River, a series of thin-bedded, bluish-gray limestones with shaly part- 

 ings that closely resemble the Ottertail limestones, and similar strata 

 occur on the northeastern slope of the Beaverfoot-Brisco-Stanford 

 Range ; presumably the greater part of the Beaverf oot River Valley, 

 as well as the Kootenay River Valley nearly to Palliser River, is 

 underlain by the Ottertail and Goodsir formations. How far north- 



' Loc. cit., p. 86. 



