120 STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 



conditions existed at few localities and in by far the greatest part 

 of the region no coal occurs. The thin lenses, referred by some 

 writers to this formation, belong rather to the Benton. 



The Kootenai. 



The Dakota, as described by the earlier students in the Front 

 Range region of Colorado and New Mexico, consists of two sand- 

 stones separated by shale of variable thickness. Darton's collections 

 in the Black Hills of northeastern Wyoming proved that the Da- 

 kota of that region is complex, that only the upper sandstone is 

 Upper Cretaceous, the other deposits belonging to the Lower Cre- 

 taceous. He was convinced that a new name was necessary and 

 offered Cloverly formation as substitute for Dakota. At a some- 

 what later time Darton, Lee and Stanton discovered somewhat simi- 

 lar conditions in Colorado and New Mexico. In Montana, this for- 

 mation proved to be practically equivalent to the Kootenai forma- 

 tion of G. M. Dawson, which is important in the Rocky Mountains 

 region within Alberta and British Columbia. This earlier name 

 has been accepted throughout ; but in some localities it appears to 

 include the upper sandstone or Dakota. The Kootenai has not been 

 recognized in Colorado and New Mexico west from the Front 

 Ranges except in the Park area of Colorado, where it was seen by 

 Beekly. Elsewhere the "Dakota" sandstone rests on a mass of 

 clays containing some sandstones, the Morrison formation, of which 

 the relations are not wholly clear, though in recent years the pale- 

 ontologists have shown increasing inclination to regard it as Lower 

 Cretaceous. It has no coal. 



The Kootenai is recorded as coal bearing nowhere south from 

 the Black Hills, where Darton gives the succession, as Dakota sand- 

 stone, lo to loo feet ; Fuson shale, lo to loo feet ; Lakota sand- 

 stone, 25 to 300 feet ; forming the Cloverly formation of his earlier 

 publications. ^^^ The Lakota, mainly sandstone, contains the coal. 

 The sandstones are mostly hard, massive, coarse and cross-bedded ; 

 but in many places they are slabby, ripple-marked and locally they 

 are conglomeratic. Lenses of coal occur near the base and at times 



II''' N. H. Darton, Folios 127, 128, 1905; Prof. Paper 51, 1906, pp. 50-53; 

 Bull. 260, 1904, pp. 429-433 ; Prof. Paper 65, 1909, pp. 12, 40-48. 



