478 J. E. TODD THE CHAXXEL OF THE MISSOURI RIVER 



DAMMING OF THE NIOBRARA RIVER 



Some years ago the writer studied the ancient channels between the 

 States of Sonth Dakota and Nebraska. The older system included the 

 Niobrara, Ponca, Mosquito, and Choteau creeks. Their altitude was 

 from 100 to 125 feet higher than the present streams occupying that 

 region. It is evident that the Niobrara, the larger one, crossed the 

 trough of the present Missouri a little east of Springfield, swept in a 

 broad curve to the north past the stations of Tabor and TJtica and merged 

 into the present course of the Missouri a few miles east of Yankton. 

 This is shown not only by the topography, but by the deposits found in 

 wells. When the extremity of the James Eiver ice-lobe reached this old 

 valley in the northern part of Yankton County, it forced the stream to 

 find its way around the edge of the ice, and so located the present course 

 of the Missouri between Bonhomme and Yankton. Judging from the 

 exposure of bedrock in the sides of its new valley, it must have cut down 

 in some places on the south side 200 to 350 feet. The level of water, as 

 before stated, was more than 100 feet higher than the old level of Niobrara 

 and its tributaries. 



BIJOU HILLS DIVIDE 



Near the southwest corner of Brule County, South Dakota, there is 

 seen a prominent and nearly continuous line of fiat-topped buttes, rising 

 300 to 500 feet higher than the surrounding country and about 2,000 

 feet above the sea. The line of buttes stretches away in the distance 

 toward the west, and only two of the buttes are east of the Missouri 

 Eiver. It may have extended farther east and the ice may have carried 

 them away. Lying up against the eastern end of the eastern butte is a 

 ridge of till or boulder-clay. The till also comes up high on the south- 

 west corner of the butte, but no northern boulders or pebbles are found 

 on top of any of the buttes. Along the northern side of the butte, just 

 east of the Missouri, numerous boulders are found, and apparently the 

 upper limit of their distribution seems to mark an old water line. The 

 height of this line is determined by a barometer for 1,880 feet above sea- 

 level. 



Opposite the mouth of the White Eiver may be found trace of the side 

 of an old channel, about 225 feet above the river, which may be traced 

 more or less clearly to Eed Lake and Pukwana, where it is 1,543 feet 

 above sealevel. The Missouri Eiver at low water at Chamberlin is 1,323. 

 White Lake, in the northwest corner of x\urora County, seems also to 

 be in this old valley, which without doubt extended to the James Eiver. 

 Between Pukwana and White Lake it is too deeply covered with boulder- 

 clay to be traced clearly. 



