FARIBAULT COUNTY. 



Glacial UVe.] 



or a gravelly and stony clay. At many places, however, in western Fari- 

 bault county and in Blue Earth county, its upper ten feet is found to- be in 

 part obscurely or sometimes quite plainly stratified. In this characteristic, 

 also, it resembles the till which generally forms the surface of the south 

 end and of the sides or outer portions of the flat Red river valley, which 

 was covered by lake Agassiz during the recession of the ice-sheet.* Much 

 of the basin that is now drained northward by the Blue Earth river, dis- 

 tinguished thus by its smoothed and sometimes partly stratified till, ap- 

 pears to have been occupied by a similar glacial lake, dammed by the 

 barrier of the waning ice-sheet of the last glacial epoch during a consider- 

 able time in which this was retreating northward and northwestward from 

 the south line of the state and from its eastern moraine, until its recession 

 uncovered the present avenue of drainage to the northeast by the Minne- 

 sota river. The hight of this lake was approximately 1150 feet above the 

 sea, making its depth in the north part of Faribault county 50 to 1 25 feet, on 

 the west line of Waseca county about 75 feet, and in the north part of Blue 

 Earth county about 200 feet. Its exact boundary can probably be traced, 

 with the aid of leveling, along considerable portions of its eastern, south- 

 ern and southwestern shores, by its beach deposits of gravel and sand. 

 When this lake attained its maximum extent, it is believed to have spread 

 far to the northwest beyond the limits of the basin of the Blue Earth 

 river.f 



The outlet of this glacial lake is found in Kossuth county, Iowa, at the 

 head of the most southern branch of the Blue Earth river, where Union 

 slough:}: occupies a continuous channel from the headwaters of the Blue 

 Earth to Buffalo creek and the East fork of the Des Moines. It is stated 

 that at the time of high water an wiinterrupted canoe voyage has been 

 made by this route from Algona on the East Des Moines river north to 

 Blue Earth City. Union slough (also frequently called the "Big slough" 



'Compare the eighth and eleventh annual reports. 

 tAt time of formation of the moraine that reaches f 



roni Kiester northwestward (page 462), this lah 



: Minnesota valley and permitted drainage to take its present course. 



JCompare Dr. C. A. White's Report on Ilif geological surrey of Iowa, 1 S70; vol . i , p. 57. 



