MAP OF NORTH DAKOTA 



471 



have inserted numbers to indicate the different arguments and also for 



reference.- 



1. "The vallev of Snake Creek is no larger than the valleys of other tribu- 

 taries entering the Missouri above this point, and the notch in the east front 



NORTH DAKOTA 



J.E.TC»0. 1921 

 EXPLANATIONS 

 Limit of the qlodal drift 

 Edqe of moximum ice sheet -. 

 Morqin d anciert Idkes 

 Moraines 



PRE-WiSOONSIN ■ 



wr SCON SIN rO>7 



Altomont I-s^i- 



Ancient Channels 



TERTIARY i-x 



PLEISTOCENE b _ j. 



AJtitude, feet atxve sea levet^o . 



Sca/e in miles c 5 lo go ap 



Figure 1.- — Map of Xorth Dakota 

 Showing probable history of the formation of the Missouri River in North Dakota. 



of the divide north of Fort Stevenson, which is shown on some maps, does 

 not exist in reality, and there is no evidence of any preglacial valley here. 

 The valley of Long Lake Creek could hardly have been the eastward exten- 

 sion of the Cannon Ball River valley, since its lower course is not opposite 



2 Bull. Geol. Soc. Am., vol. 27, p. 295. 



