534 



A. G. LEONARD 



The Fort Union is remarkably uniform in color, composition, and 

 appearance throughout the region under discussion. The prevail- 

 ing color is either a light ash gray or yellow, but in places the beds 

 are nearly white. In Billings County, North Dakota, an upper 

 member of the formation appears in the tops of the higher ridges, 

 divides, and buttes, and resembles somewhat the Lance beds in 

 its dark gray color and its many brown ferruginous, sandstone 

 concretions. The lower member constitutes the typical yellow 



r -. 



Fig. o. — Two coal beds on Little Missouri River in northern Billings County, 

 North Dakota. Upper bed is ten feet thick, the lower is near river level. 



and light gray Fort Union and this is the only one present over 

 most of the region. Where both occur, the contrast between the 

 upper and lower members is so well marked and their contact so 

 clearly defined that it can be readily distinguished even at a dis- 

 tance and traced without difficulty, wherever it is exposed. Over 

 nearly one-half of Billings County a thick coal bed or layer of 

 clinker formed by the burning of the coal occurs just at the con- 

 tact. The strata forming both members of the Fort Union are seen 

 along the Northern Pacific Railroad between Fryburg and Medora, 



