CRETACEOUS AND TERTIARY FORMATIONS 



535 



North Dakota. From the former station to the siding at Scoria, 

 the upper member is well shown in the badlands on either side, 

 while between Scoria and Medora the lower member appears. 



Over a large area in southwestern North Dakota, the Fort 

 Union is formed in part of white, sandy clays and very pure plastic 

 clays, which differ from any of the beds found elsewhere. They 



Fig. io. — A mass of burned clay or clinker formed by the burning of a thick coal 

 bed. Mouth of Deep Creek, Billings County, North Dakota. 



occur in Stark and Dunn counties and adjoining portions of the 

 surrounding counties, where they are restricted to the tops of the 

 higher ridges and divides or to an elevation of from 2,450 to 2,600 

 feet above sea-level. Near their eastern border they lie about 

 600 feet above the base of the Fort Union and their maximum 

 thickness is 150 feet. These white, sandy clays are well seen 

 near Dickinson and Gladstone, and several miles north of Hebron. 

 The Fort Union formation everywhere contains numerous 



