STRATIGRAPHIC POSITION OF LANCE FORMATION 363 



tion in the section. Above the Fox Hills, but, as will be shown 

 later, with the intervention in places of a distinct unconformity, 

 comes the Lance formation, above which, but without unconformity 

 or other observed break, is the acknowledged Fort Union. 



In the present connection the principal interest naturally centers 

 in the Lance formation, and more particularly as regards its rela- 

 tion with the underlying Fox Hills. Mr. Calvert, who is not only 

 familiar with the area in question but with adjacent areas in North 

 Dakota and Montana where similar conditions obtain, has kindly 

 prepared the following statement: 



" Stratigraphic work by field parties in immediate charge of 

 A. L. Beekly, Max A. Pishel, and V. H. Barnett in the Standing 

 Rock and Cheyenne River Indian Reservations of North and 

 South Dakota in 1909 and similar investigation in eastern Mon- 

 tana in 1910 in charge of Max A. Pishel and C. F. Bowen gave 

 opportunity to study the relationship of several formations con- 

 cerning which discussion has arisen periodically for a number of 

 years, and which is of special interest in view of its direct con- 

 nection with geologic history at the close of the Cretaceous. The 

 region studied in the Dakotas includes the type locality of the 

 Fox Hills sandstone and is adjacent to the type locality for the 

 Pierre shale. Where the full section of the Fox Hills is present it 

 usually comprises a gradation at the base from the somber shale of 

 the typical Pierre into a more or less massive sandstone. This sand- 

 stone member is overlain by 25 feet or more of banded shale over- 

 lain in turn by a massive sandstone, constituting what in the field 

 was considered the top member of the Fox Hills. Fossils occur only 

 sparingly in the lower sandstone and in the banded shale, whereas 

 the top sandstone is prolifically fossiliferous, the -fossils being found 

 most abundantly at or near the top of that member. Normally 

 overlying this fossiliferous horizon is a sequence of beds entirely 

 dissimilar in lithology from the underlying Fox Hills, and it is 

 concerning these beds that question has arisen relative to their 

 exact position in the geologic column. These strata constitute 

 the Lance formation to which the name 'somber beds' has been 

 applied in various previous publications. 



"From the standpoint of lithologic character the term 'somber 



