266 THE GLACIAL LAKE AGASSIZ. 



LAKE DAKOTA. 



Prof. J. E. Todd supplies me the approximate outline ot" a lake named 

 by him Lake Dakota, v\hich occupied the valley of the James or Dakota 

 River contemporaneously with the foregoing, reaching from Mitchell 170 

 miles north to Oakes aud varying from 10 to 30 miles in width.^ It out- 

 flowed st>uthward by the present course of the James to the Missom-i. The 

 Dakota ice-lobe, which had filled this valley and in its recession formed the 

 northern shore of Lake Dakota, was not thei'efore the cause of this lake in 

 the same way that the "lake in the Blue Earth and Minnesota basin and 

 Lake Agassiz owed their existence to the barrier of the ice-sheet in its 

 retreat The bed of Lake Dakota has a nearly uniform elevation of 1,300 

 feet, or is within 10 feet below or above this, throughout its length; and 

 during the glacial recession it was covered by a lake whose shores have 

 now a height of aboiit 1,300 to 1,350 feet, probably ascending slightly from 

 south to north as compared with the present sea-level. Professor Todd 

 states that the surface of this lacustrine area in its southern part, from 

 Mitchell to Redfield, is nearly flat till, but thence northward is sand and 

 loess-like silt, while considerable tracts of the eastern border of its north 

 part consist of low dunes. 



The outflowing James River was cvitting down its channel during the 

 retreat of the ice-lolje, and its erosion was so rapid as to prevent the north- 

 ern part of Lake Dakota from retaining sufficient depth to outflow eastward 

 into the south end of Lake Agassiz when the way was opened by the far- 

 ther departure of the ice, receding from the Head of the Coteau des Prai- 

 ries and beginning to uncover the Red River Valley. A large tract of the 

 sand and silt beds of Lake Dakota, and of a contiguous glacial lake formed 

 in Sargent County, N. Dak., at the time of the Dovre moraine (p. 148), 

 now sends its drainage to the Red River by the head stream of the Wild 

 Rice, which passes north of the Head of the Coteau and enters the area of 

 Lake Agassiz near Wyndraere. The lowest portion of the watershed on 

 this lacustrine deposit, over which the James River would flow east to the 

 Wild Rice River, is scarcely 10 feet above the general level of the James 

 Valley, or 25 feet above the present level of the James River, being at 



•This lake is partially mapped by Prof. Todd iu Proc. A. A. A. S., Vol. XXXIII, 1884, p. 393. 



