STEVENSOX— INTERRELATIONS OF FOSSIL FUELS. 109 



feet higher and a third at the top, but coaly material is present in 

 other portions as carbonaceous shale. The highest coal is found in 

 the northern part of the county, but it disappears south from Valier, 

 about 50 miles from the International Boundary and no trace of it 

 has been found farther south in a distance of not less than 50 miles. 

 It is thin in Teton County but increases toward the north beyond 

 the boundary and is 6 feet thick at Lethbridge, where the coal is 

 good. The seams of the middle zone are thin and yield only im- 

 pure coal, while the lower zone has two seams which are persistent 

 in the Valier district on the easterly side of the county. The upper 

 one is 2 feet 6 inches, with 2 feet of coal, while the lower one, with 

 extreme thickness of 5 feet 8 inches, contains only 8 inches of clean 

 coal. These seams vary much in thickness, but the upper one is 

 mined. Samples of clean coal gave 14.07, 13.9, 14.5 and 28.6 per 

 cent, of ash. 



Dowling,^- in his synopsis of conditions in the western states of 

 Canada, says that the depressions, in which ^lesozoic rocks were 

 deposited, appeared in the Rocky Mountain area, where Triassic 

 and Jurassic beds are found. The Jurassic sea invaded a narrow 

 depression, now elevated as the Rocky Mountains and the Foothills. 

 Land conditions prevailed during part of the Lower Cretaceous, 

 but occasional submergences extended to a short distance toward 

 the east, whereas in the United States they extended as far east as 

 the Black Hills of Wyoming. Alore general submergence east- 

 wardly came in the L^pper Cretaceous, while on the western side 

 there is evidence of shallowing during the earlier periods. Marked 

 proof of shallowing on that side is evident during the Montana, for 

 land conditions are shown by the coal seams and by the type of 

 sediments, but marine conditions prevailed at the east. Submerg- 

 ence followed and the sands at the west were covered with marine 

 shale. The closing part of Cretaceous time was characterized by 

 emergence, with brief periods of submergence, as shown by land 

 and shallow water conditions, giving an abundant flora and a 

 brackish-water fauna : this closing stage is the Edmonton-St. Mary 

 formation. The vast accumulations unsettled the equilibrium of 

 the area whence they had been derived and, toward the close of the 



0- D. B, Dowling, Geol. Survey of Canada, ^lem. 53, 1914, pp. 32, t,3- 



