CRETACEOUS AND TERTIARY FORMATIONS 517 



most abundant toward the base of the formation, where, in some 

 places, they pass gradually into the Pierre shale. It will be seen 

 from the above lists that some of the fossils occurring in the upper 

 part of the Pierre range up into the Fox Hills. The top of the latter 

 is better defined than its base, the change from it to the overlying 

 Lance beds in some places being abrupt, but generally the two are 

 conformable. The Fox Hills beds vary in thickness from seventy- 

 five to two hundred feet. 



LANCE FORMATION 



The Lance beds have a wide distribution in North Dakota and 

 eastern Montana, as well as in northwestern South Dakota and 

 northeastern Wyoming. The largest area in North Dakota is 

 in the south-central part of the state, where this formation occupies 

 a large part of Morton county and all of the Standing Rock Indian 

 Reservation, outside the Fox Hills and Pierre outcrops; east 

 of the Missouri River, it covers southern Burleigh and the greater 

 part of Emmons County, together with adjoining portions of 

 Kidder, Logan, and Mcintosh counties. In the southwestern 

 corner of North Dakota is a second smaller area stretching along 

 the Little Missouri River for a distance of over fifty miles in western 

 Bowman and southern Billings counties. In eastern Montana 

 the Lance beds are found along the Yellowstone River from the 

 vicinity of Forsyth to a point about fifteen miles below Glendive. 

 South of the Yellowstone, these beds are exposed along the valleys 

 of the Powder and Tongue rivers and their tributaries. The 

 badlands occupying a wide strip of country on the south side of 

 the Missouri River in northern Dawson County are for the most 

 part formed of Lance beds, and they extend as far east as Brockton. 

 According to C. D. Smith 1 the formation is found on the Fort 

 Peck Indian Reservation, and the beds also occur west and north 

 of the reservation in Valley County, Montana. 



South-central North Dakota area. — In Morton County, North 

 Dakota, numerous good outcrops of the Lance formation appear 

 along the Missouri, Cannon Ball, and Heart rivers and many of 

 the smaller streams (Fig. 4). The beds are found along the Mis- 



1 Bull. U.S. Geol. Surv., No. 381, 39. 



