36 THE ROYAL SOCIETY OF CANADA 



Farther north the shales are found in the foothills west of Calgary 

 while indications of shore deposits intercalated in the beds in the Big- 

 horn basin show an approach to a shore line in that area. 



In the Montana section these deposits are called the Claggett 

 shales and, although containing some sandy material, are mainly 

 of dark grey shale with many clay-ironstone nodules. The formation 

 is very much of the same appearance as the Pierre of the plains and 

 is particularly rich in the smaller marine invertebrates. The thickness 

 of the deposit varies from a maximum in the east to a minimum in 

 the west, but it is nearly 500 feet in thickness at the longitude of Medi- 

 cine Hat. The formation in the south was first described at Fort 

 Claggett on the Missouri river and the formational name has been 

 retained in the nomenclature of southern Alberta. In the foothills 

 north of the North Saskatchewan river the middle part of the Brazeau 

 formation is made up of shales and thin sandstones that suggest a 

 near-shore marine or brackish-water deposit. The upper members are 

 probably of freshwater deposition and as such show the probable 

 beginning of the retirement of the sea. The shales of the Athabaska 

 section show no division between the Colorado and Montana forma- 

 tions, so that the inference is that the upper part of the La Biche 

 shales corresponds to this lower Pierre member. On Smoky river, a 

 southern branch of Peace river, the shore deposits corresponding to 

 the lower member of the Belly River overlie the Benton ; but marine 

 shales with a Pierre fauna are found above them. That these shales, 

 called the Smoky River shales, belong to the lower part of the Pierre 

 is evident in the section in the vicinity of Table mountain just south 

 of Pine river. The shales overlying the coal-bearing Dunvegan 

 sandstones are estimated by G. M. Dawson as being 350 feet in thick- 

 ness^ in the Smoky River section and are overlain by about 1,700 

 feet of beds in Table mountain. The top members of the Table Moun- 

 tain section are sandstones 200 feet thick and probably are locally 

 hardened as they have been removed from the country to the east. 

 In the plateau country through which the Wapiti river has cut a 

 channel just to the southeast, the Wapiti sandstones, apparently 

 not exposed on the slopes of Table mountain below this strong sand- 

 stone, cover a large area and have been referred, on account of their 

 coal-bearing character, to the Laramie. This correlation should be 

 revised owing to the uncertainty of the meaning of the term; but in 

 this connexion it should be pointed out that in the beds at the summit 

 of Table mountain marine sandstones appear holding Inoceramus 

 altus a species fo und in the Pierre shales of Wyoming.^ Therefore 



1 Rep. of Progress 79-80, p. 125B. 



2 Idem. p. 117B. 



