526 E. RUSSELL LLOYD AND C. J. HARES 



CRETACEOUS SYSTEM 

 FOX HILLS SANDSTONE 



The type locality of the Fox Hills sandstone is Fox Ridge in 

 the Cheyenne River Indian Reservation in South Dakota between 

 Moreau and Cheyenne rivers and about 25 miles northwest of 

 the mouth of the latter stream/ This region was examined in 

 detail by V. H. Barnett in 1909, and the formation was mapped by 

 Barnett and other geologists of the U.S. Geological Survey north- 

 ward to Cannonball River. ^ The Fox Hills is made up of massive 

 gray, yellow, and buff sandstone and banded shale, the maximum 

 thickness in the Standing Rock and Cheyenne River Indian reser- 

 vations being 400 feet and the average about 150 feet. Around 

 the southern end of the Glendive anticline in Billings and Bowman 

 counties, North Dakota, the Fox Hills sandstone is about 75 feet 

 thick. It has been shown that in some localities in the Dakotas 

 and eastern Montana^ the overlying Lance formation is uncon- 

 formable on the Fox Hills, the contact between the two being 

 marked by erosion channels in the Fox Hills sandstone. In one 

 locality in the Standing Rock Reservation the Fox Hills is 25 feet 

 or less in thickness, so that either the erosion interval represented 

 is of considerable magnitude or else the formation is peculiarly 

 variable in thickness. This evidence of unconformity is, however, 

 vitiated by the presence in the Standing Rock Reservation of a 

 bed above the line of unconformity containing brackish water 

 and marine fossils and along Little Missouri River by the grada- 

 tion by alternation of beds of Fox Hills character with those of 

 Lance character. The evidence both for and against the supposi- 

 tion of an unconformity of major importance at this horizon is 

 fully discussed in the papers cited. From the stratigraphic stand- 



' The name was first used by Meek and Hayden, Acad. Nat. Set. Philadelphia, 

 Proc, XIII (1862) 419. 



2 W. R. Calvert and Others, op. cit.; T. W. Stanton, "Fox Hills Sandstone and 

 Lance Formation ('Ceratops Beds') in South Dakota, North Dakota, and Eastern 

 Wyoming," Am. Jour. Sci., 4th ser., XXX (1910) 172, 188; F. H. Knowlton, "Further 

 Data on the Stratigraphic Position of the Lance Formation ('Ceratops Beds')"; 

 Jour. Geol. XIX (1911) 358-74. 



^ F. H. Knowlton, op. cit. 



