PLATE XXX. 



LE SUEUR COUNTY, 1884. WARREN UPHAM. 



This county presents the widest diversity of natural surface dependent on the 

 drift and the forces that produced the drift. A broad morainic tract extends along 

 its eastern border, and also along its southern. The interior of the county, included 

 in the angle between these rough belts, was later largely occupied by a lake caused 

 by the obstruction of the Minnesota valley by the retreating glacier at a point further 

 north. This lake had its latest outlet by way of the valley occupied by lakes Tetonka 

 and Sakata and the Cannon river to the Mississippi, and was another descendant of 

 that which formerly extended over much of Waseca, Blue Earth and Brown counties, 

 having its discharge by way of the Des Moines. Such glacial water, wherever pres- 

 ent, leveled the till surface when the till was in the act of deposition by the glacier 

 not only by abstracting the clayey element and spreading it in the depressions further 







south from the ice border, but by facilitating the even spreading of the till itself. 

 Add to this contrast the phenomena of the valley of the Minnesota river, which are 

 largely dependent on the action of the drift forces, and it becomes apparent that few 

 if any counties of the state offer greater variety of topography or embrace a broader 

 scope of glacial features. 



The broad, gravelly terraces, rising 150 feet above the Minnesota river, seen at 

 Kasota, Le Sueur and northeast from Ottawa and elsewhere between Mankato and 

 Fort Snelling, are remnants of a coarse bottom-land of the river, through which the 

 later river has cut its present channel. When this elevated bottom-land was formed 

 the drift was being accumulated, for there is no possible source of the clean, coarse 

 gravel of which these terraces consist, except the till in the act of deposition. The 

 northern portion of the Minnesota valley being ice-bound in the glacier, this bottom- 

 land must have been near the level of outflow of the glacial lake that then covered 

 the region, and hence the drainage was toward the south. The lower terraces which 

 rise about 110 feet above the river, seen at Le Sueur, were formed in a similar way, 

 at a later date, probably at the time the outlet was through the Cannon valley. 



This county is within the " big woods," and was originally timbered with a great 

 variety of deciduous trees. The streams furnish some water-power, where flouring 

 and sawmills are in operation. The magnesian limestones at Ottawa and Kasota are 

 quarried for lime and building stone. In the crevices of these rocks at Ottawa are 

 deposits of a kaolinic clay, similar to that seen at and near Mankato, whose origin 

 dates from before the Cretaceous, though probably spread by the Cretaceous ocean. 

 This magnesian limestone is in the Upper Cambrian. That at Clapp's limekiln, near 

 Caroline station, is of the Shakopee, and that at Ottawa and Kasota is of the Lower 

 Magnesian proper. N. H. w. 



