152 GEOLOGY. 



In the northern part of the United States (Montana) and in the 

 territory beyond (Alberta), a large area of deposition appears to have 

 come into existence at about the beginning of the Montana epoch. 

 The deposits made in it constitute the Belly River formation, which 

 is believed to be, at least in part, contemporaneous with the lower por- 

 tion (Ft. Pierre) of the Montana series. Here also belong the Judith 

 River beds. 1 Like other parts of the Cretaceous system, this formation 

 contains some coal. The Pierre formation also yields oil at Boulder, 

 Colo. 



The Laramie. 2 — In the Laramie epoch, the submerged area of the 

 western interior was still further contracted, and partially shut off 

 from the ocean, and over a large area, in the Great plains and west 

 of them, an area perhaps 2000 miles long and 500 miles wide, depo- 

 sition was taking place in water which was sometimes salt, some- 

 times brackish, and sometimes fresh. Some of the deposits, too, were 

 made in marshes and on low lands, rather than in water. In general, 

 the area of deposition seems to have been near the critical level, and 

 for a long time maintained a halting attitude, now above the sea and 

 now below it. When below, it was so slightly below as not to bring 

 about strictly marine conditions, and when above, it was so slightly 

 above as to be in large measure unclrained, or poorly drained. The 

 Laramie series may be said to record the transition from the marine 

 conditions of the Montana epoch, to the fresh water and land condi- 

 tions of the Tertiary in the region concerned, just as the Coal Measures 

 of the eastern interior represent the transition from the marine con- 

 ditions of earlier times, to the terrestrial and lacustrine conditions of 

 the Permian. 



The general area of deposition is shown in Fig. 388. To the east 

 the Laramie is concealed by younger beds, preventing the accurate 

 determination of its border. To the north it reaches to the Lesser 

 Slave lake, and perhaps beyond. 3 To the west, its border is often 

 concealed by overlapping lava-flows. 4 To the south, its limit is uncer- 



1 Hatcher and Stanton, Science, Vol. XVIII, p. 212. 



2 For a full discussion of the Laramie, see White (C. A.) Bull. 82, U. S. Survey. 

 A brief statement by the same author is found in the Proc. A. A. A. S., 1889, Vol. 38. 



3 McConnell, Geol. Surv. of Can. Am. Report, Vol. V, Pt. I. See also Dawson, 

 Can. Geol. Surv. Rept. of Progress, 82-84, and Tyrrell, Ann. Rep. II for the Lara- 

 mie north of the United States. 



4 Dutton, High Plateaus of Utah. 



