90 



supposed to have formed but a very thin sheet east of the 

 mountains. The base of the formation is a heavy bed of 

 sandstone, which is succeeded by sandstones and shales 

 containing many coal seams. A bed of conglomerate 

 divides the formation in its northward extension, and few 

 coal seams are found in the lower part. In the south 

 the thicker seams are in the lower part. The greatest 

 thickness occurs in the mountains and on Elk river in east- 

 ern British Columbia. Near Banff in Alberta the thickness 

 is about 3,700 feet (1,127 m -)- I n the Bighorn basin this 

 thickness continues. Eastward at Moose mountain it 

 is only some 375 feet (114 m.). The fossils of the forma- 

 tion are plants, such as ferns, cycads, and conifers. 



Dakota. — In the mountains above the coal bearing 

 formation, occurs a series of conglomerates and sandstones 

 that is not distinctly coal bearing, although thin coal 

 streaks occur in it. Fresh water conditions prevailed 

 in the mountain section and on the eastern margin during 

 this period of deposition. In the lower part of Athabaska 

 valley, the upper beds at least contain marine fossils. 



The thickness of the formation in Manitoba cannot 

 be much more than 200 feet (61 m.). In the foothills 

 a thickness of 950 feet (290 m.) seems to represent the 

 whole formation; but, westward in the Elk river escarp- 

 ment, a shore deposit thousands of feet in thickness occurs 

 at this horizon. 



Benton. — Dark grey, almost black, shale of marine 

 origin, forms a continuous sheet probably across the 

 whole interior basin. In Manitoba the deposit is about 

 175 feet (53 m.) in thickness. In the foothills it is over 

 700 feet (213 m.), but this undoubtedly includes part 

 of the overlying Niobrara. The entombed forms of animal 

 life include Inoceramus problematicus, Scaphites ventricosus 

 and Prionscyclus woolgari. 



Niobrara. — In Manitoba, this formation consists of 

 grey calcareous shales, which are an upward continuation 

 of the Benton. Westward it is not so characterized in 

 the marginal deposits there, since a period of unrest in the 

 mountains occurred about that time accompanied by brief 

 retreats of the shore line due to a slight rising of the crust. 

 The formation is from 130 to 200 feet (40 to 61 m.) thick 

 in the eastern part. The presence of foraminifera is 

 a characteristic feature of the formation. The fossils 

 include Serpula semicoalita, Ostrea conjesta, Anomia obliqua, 



