288 Annai.s of the Carnegie Museum. 



The Lower White River beds in North Dakota, at least some of them, 

 resemble portions of the beds of nearly the same age in Montana ; but 

 the Middle White River is different in appearance in the two places. 



It is evident that the later Tertiary deposits in Montana accumu- 

 lated in various ways (as water-borne sediments and wind-blown dust 

 accumulating in lakes, marshes, and streams, and as sheet-wash and 

 flood-plain deposits, etc.), in large river valleys excavated in later 

 Eocene times. 



I have little doubt that the upper Tertiary deposits in North Dakota 

 were also deposited in broad valleys of erosion. Much of the material 

 of the deposits came from areas of granite and quartzite rock. In 

 the region of the Black Hills are the only outcrops of these rocks for 

 hundreds of miles ; this, connected with the fact that a series of re- 

 mains of Oligocene deposits have been observed to extend from 

 Dickinson to the Black Hills, suggests the probability that a river 

 formerly flowed from the Black Hills northeastward through this 

 region. If this be true, there should be coarse sediments as the 

 mountains are approached, which is probably the case. Another 

 thing, which tends to confirm the idea that these are river- valley de- 

 posits, is the fact that, scattered over the plains, there are buttes ap- 

 parently as high as White Butte, but which are not capped by later 

 Tertiary beds. However this may be, it will undoubtedly be possible 

 to trace approximately the courses of some of these ancient rivers 

 eastward from the Cordilleran region. 



Apparently the Middle White River was deposited after consider- 

 able erosion of the Lower White River. I have not seen much evi- 

 dence of erosion of the Middle White River (Oreodon) beds, previous 

 to the deposition of the Upper White River, but the latter was evi- 

 dently accumulated under more complex conditions, portions of the 

 deposits being eroded and refilled with stream-deposits, etc. In the 

 Little Bad-lands in one place what appears to be the channel of a 

 river, or small stream, has been excavated in the clay, and afterward 

 refilled with water-worn sand. 



