STRATIGRAPHIC POSITION OF LANCE FORMATION 367 



ently the same horizon as that in the Dakotas tends to show that 

 the break has more than local significance." 



The observations recorded by Mr. Calvert in the eastern portion 

 of this South Dakota field were supplemented and extended to the 

 western part of the state by Mr. V. H. Barnett in 1910, while 

 making a hasty reconnaissance trip across the country. For 

 instance, on the south bank of the Moreau River, near Govert P.O., 

 in Sec. 21, T15N", R8E, South Dakota, Mr. Barnett found what 

 is perhaps the most marked evidence yet recorded of unconform- 

 able relations between beds thought to be Fox Hills and the Lance 

 formation. Mr. Barnett traced the Lance formation continuously 

 from the central part of the state to the point mentioned above, 

 where it was found practically horizontal, while the underlying 

 beds dip to the northwest at an angle of about io°. These under- 

 lying beds appear to be in the stratigraphic position of, and litho- 

 logically similar to, beds resting immediately on Pierre shale, at 

 Hoover, about 10 miles southwest, and there is no reasonable doubt 

 regarding their age, but no paleontologic evidence was secured — 

 or sought — at this locality. If the beds are not of Fox Hills age 

 they must be older, which would indicate an unconformity of even 

 greater magnitude than is presumed. Mr. Barnett secured a 

 photograph of this section which he has kindly permitted me to 

 reproduce here as Fig. 1. The full section of the supposed Fox 

 Hills is not exposed at this point, but some distance west, at Castle 

 Rock Butte (T12N., R5E), the following section was measured; 

 Pierre 50 feet; Fox Hills 125 feet; Lance formation 140 feet, the 

 latter overlain by higher Tertiary. 



The unconformity spoken of above by Calvert as occurring 

 in Sec. 32, T7N, R61E, in Custer County, Montana, is on the 

 west side of the anticline extending southeast from Glendive. It 

 is clearly shown in the accompanying Figs. 2, 3, the negatives 

 of which were made by Mr. C. F. Bowen, by whose consent they 

 are included here. The Fox Hills with a thickness of about 

 70 feet dips at an angle of 5 , while the overlying Lance formation 

 is horizontal. 



Mr. Calvert's observations concerning the occurrence of the 

 marine Fox Hills invertebrates in the basal members of the Lance 



