200 KNOWLTON 



Little Missouri River. The valley of this stream, according to 

 Leonard and Smith,2° has a depth of 420 to 440 feet below the sur- 

 face of the plain in which it has been eroded, and may have cut into 

 the beds of the lower member, though the deep well sunk at Medora 

 carries the section down for a distance of 940 feet below the lowest 

 beds exposed in the region, and this, on the basis of the thickness at 

 Glendive, must be near to the base of the section. The entire thick- 

 ness of the section in this area, including the beds passed through by 

 the Medora well, is 1720 feet, and it is possible that the upper por- 

 tion of the lower member of the Fort Union may be exposed, but as 

 this is not definitely known it is omitted from present consideration. 

 In any event all of the numerous finely preserved plants obtained 

 in this region are distinctly of Fort Union age. 



10. BISMARCK, NORTH DAKOTA, AND VICINITY. 



To the eastward of Medora along the line of the Northern Pacific 

 Railroad Fort Union plants have been collected at a number of points, 

 as at Lehigh, Dickinson, Sims, etc., but as the stratigraphic relations 

 are not definitely known through this region, w-e may pass on to 

 Bismarck, North Dakota, where the lower member is undoubtedly 

 present. Near the mouth of Apple Creek, about 10 miles southeast 

 of Bismarck, are exposures of soft sandstones and clays of dark-gray 

 color which form a bluff 75 to 100 feet high. Near the base of this 

 bluff at a point i^ miles above the mouth of Apple Creek the following 

 very fragmentary plants were obtained: 



Adiantum? sp, 

 Salix sp. 

 Quercus sp. 

 Ficus sp. 

 Launis? sp. 

 Carpites sp. 



The beds mentioned above are not the base of the lower member 

 of the Fort Union, but at a pointonthcweslsideof the Missouri River 

 about 20 miles below Mandan, Dr. T. W. Stanton obtained the fol- 



" Bull. U. S. Geo!. Surv., 341A, 1908, p. 15. 



