4<G J.E.TODD THE CHANNEL OF THE MISSOURI RIVER 



since the Glacial period, but really they are no more significant of the 

 preglacial age of the channel than are the bonlders which are considered 

 nnder head number 2. It seems probable that the accumulation of 

 l)oulders mentioned has been formed some time since the Glacial period, 

 and the later erosion of the stream has left it as a low terrace. 



In the same region, river gravels containing glacial boulders are found 

 at a much higher elevation at Glass Bluff,^ about 4 miles southeast of 

 Buford. There "glacial drift" is found resting upon Laramie strata 200 

 feet above the river. Dr. Leonard reports three localities showing 

 similar relations of drift to underlying rocks, one being a few miles 

 below Glass Bluff and another at White Earth Creek north of the Mis- 

 souri. Several other localities showing similar position by their altitude 

 above the river are not given.^ 



Bauer reports several feet of drift gravel cap|)ing flat-topped buttes or 

 fragments of a terrace along the lower course of the Little Missouri 

 Eiver.^ He thinks the}' may be of late Tertiary origin. These gravel 

 beds are strong evidence that the plane of drainage has been for some 

 time at that level since the beginning of the Glacial period. If the ])ed 

 of the Missouri were as deep as Dr. Leonard believes, before the coming 

 of the ice, what filled the valley of the stream to force the water so high 

 above the bottom of the valley ? If the glacier advanced, it might fill ^^lie 

 valley with till, but we can scarcely believe that later erosion would carry 

 it away. It would resist erosion more readily than the surrounding 

 Laramie beds. We therefore consider that the existence of these gravel 

 beds is a strong argument against the preglacial excavation of the valley. 



Evidence from South Dakota 

 gexeral statement 



According to Dr. Leonardos view, at the beginning of the ^Yisconsin 

 stage the Missouri Eiver was flowing at as low a level as. or even lower 

 than, at the present time throughout its course in the State of Xorth 

 Dakota. 



The State of South Dakota was also partially overspread with ice from 

 the same Keewatin center. It pushed against the eastern edge of the 

 Missouri Coteau in a similar way, but the coteau was more interrupted, 

 or less continuous, so it did not offer the same resistance as in North 

 Dakota. Moreover, it was moving in a river valley upon alluvial deposits, 

 which no doubt made its progress more easy and rapid. 



''' Third Biennial Report of the North Dakota Geol. Surv., pp. 80-8C. 

 " .Journal of Geology, vol. 23, pp. 53-55. 



