300 D. B. DOWXING — CRETACEOUS SECTION IN SOUTHERN ALBERTA 



there is a better chance of some of the beds reaching those of the Cascade 

 formation of Montana, which are correlated by plant remains with it. 



This formation is of great economic importance, owing to the rich coal 

 deposits contained within its beds. On Elk river there are 22 seams, 

 aggregating 216 feet of coking and steam coal. At Blairmore 21 seams 

 of a total thickness of 125 feet, and at Moose mountain there are 7, two of 

 which are workable, having 8 and 7 feet of coal respectively. In Mon- 

 tana, where the formation seems thinner, one workable seam is found near 

 the top of the formation. In the Black hills, coal-bearing beds which 

 seem to occupy eroded valleys in the Jurassic are reported. 



Dakota 



Light colored, hard sandstones, with conglomerate at base, 150 feet. 



As no fossils were here detected, these sandstones are supposed to rep- 

 resent the horizon that is above the conglomerates of the basin within 

 the mountains, and, as the formations originally constituted a continuous 

 sheet, the supposition will probably be borne out by the subsequent finding 

 of fossils. On the north branch of the Oldman river Doctor Dawson ob- 

 served a bed of ash rock at the top of the formation. This was again 

 more extensively developed near the Crows Nest pass. The Moose Moun- 

 tain locality seems to be beyond the limits of this volcanic ash and the 

 formation passes to a black shale above, which is probably Benton. In 

 the locality just mentioned Doctor Dawson collected from the sandstones 

 just below the ash bed plant remains similar to the Dakota flora, and on 

 the middle branch of the north fork, Oldman river, from a horizon above 

 the conglomerate beds, a series of plants which have affinity with both 

 the Dakota and Kootanie — that is, of five species recognized a fern and 

 two conifers occur in the Kootanie and one of the two species of dicoty- 

 ledons was originally described from the Cretaceous of Vancouver island 

 generally placed at about the Dakota horizon. 



There is thus in the thicker part of the formation a trace of the change 

 from the flora of the Kootanie to that of the Dakota. 



As marine beds, mostly shales, holding Benton fossils are found above 

 the ash beds at the localities just cited, and also occur in the Moose Moun- 

 tain section, the sandstone series beneath should represent the same depo- 

 sition, but of greatly diminished thickness in the latter locality. The 

 diminished thickness of the beds in the Moose mountain point to a pos- 

 sible time hiatus between the top of the Kootanie and the base of the 

 Dakota. Attention to this is also drawn by Mr Ward in the Black Hills 

 section. The complete section is probably to be found only in the Rocky 

 mountains. Fresh-water conditions during this period prevailed in Da- 

 kola and Montana and probably along the western margin, but northward 



