662 THE GEOLOGY OF MINNESOTA. 



[Moraines and gravel. 



tie country lying next east. It is. on the contrary, rather lower than the prairie upland, and on 

 approaching it from the east the country seems simply to be affected by a generally undulating 

 and rolling timbered descent to the river valley. 



In delineating the morainic belts through Steele county, the outer one is shown to be sud- 

 denly deflected toward the east at a point about two miles south of Aurora station, and to extend 

 in a broad curve through the eastern portion of that county, becoming continuous with this rolling 

 tract in southeastern Walcott, in Rice county. If, instead of this sudden deflection toward the 

 east, the outer moraine could have been traced through Somerset and, by way of Owatonna, into 

 the northeastern part of Deerfleld, it would then have maintained more nearly its normal course, 

 and would also have articulated perhaps more completely, upon the outer morainic belt that crosses 

 Rice county. It would also afford the usual explanation for the gravel terrace that accompanies 

 the Straight river in Steele county, as seen at Medford. But it seems very reasonable and very 

 probable that the line of accumulation should, at favorable places, be double, even during the same 

 general period of accumulation ; and that the action of the waters of the upper portion of the 

 Straight river was such as to aid such apparent duplication. The effect of this moraine on the 

 Straight river, where it crosses it in the northern part of Walcott township, was to dam it up, 

 during the existence of the ice, producing a lake covering those portions of Walcott and Medford 

 townships that lie below about 1150 feet. This lake had its outlet through Walcott township into 

 the north branch of the Zumbro river. This fact requires the moraine at this time in Walcott, on 

 the west side of the Straight river instead of on the east ; and yet it is probable that at a slightly 

 earlier period of time, it was heaped up farther east as represented on the map of Steele county. 



Gravel and gravel terraces. The Cannon valley, through its whole course 

 in Kice county, after entering it from Le Sueur county, is accompanied by 

 abundant gravel deposits. The Prairie creek valley, in Northfield town- 

 ship, is also accompanied with abundant gravel. The same is true, but to 

 much less extent, of the Straight river south of Faribault, and of the north 

 branch of the Zumbro. Everywhere this gravel is of a gray color, and was 

 derived from the blue till by drainage and wash from the ice-fields that 

 spread over the most of the county in some portion of the glacial epoch. 

 At the east end of Cannon lake the gravel of the beach is about one half 

 limestone. In no place in the county has a red gravel been seen, such as 

 appears in some places in Dakota county, referable to the red till. 



Straight river terraces, it these gravel deposits be described in the order of their age, prob- 

 ably those of the Straight valley would come first. They lie highest and farthest south. They 

 were deposited at the time of the last glacial epoch when the Straight river was dammed up by 

 glacier ice and morainic accumulations a few miles south of Faribault, and north of Walcott 's 

 mill, so as to find an outlet to the Mississippi at a much higher level than it now has. In the 

 still earlier part of the same period these waters, still closer confined by a greater extension of the 

 ice, probably had a feeble, interrupted discharge southward through the old channels, though nar- 

 row and shallow, that cross the divide in Steele and Freeborn counties, reaching the Cedar or the 

 Shell Rock river. But at the time of the most rapid accumulation of the gravel as it appears in 

 Rice county along the Straight river, the water of that valley had its discharge through the north 

 branch of the Zumbro eastward, through the broad valley that crosses Hichland, now mainly occu- 

 pied by a conspicuous grassy marsh that gives rise to the north branch of the Zumbro. These 

 gravel deposits are found southward from the northeast quarter of sec. 17, Walcott, on the west 

 side of the river, to the south county line, and to Medford, at least, in Steele county, where the flat 

 terrace on the east side of the river, on which the village is built, consists of gravel, having an 

 elevation of 1008 feet above the sea. This terrace, which begins first distinctly near Walcott's 

 mill, seems to be only an alluvial flat subject to overflow by the present river, bounded on the west 



