IOWA ACADEMY OF SCIENCE 
247 
the railway southeast of Shindlar, is ‘Wisconsin. It is believed rather, 
that the amount of Wisconsin drift is small, amounting to only a few 
feet of material much like the Kansan and grading downward into 
the true Kansan. Detailed work in the region will however, probably 
show that the Wisconsin drift does differ slightly from the Kansan so 
that it will be possible to differentiate the drifts. But should this not 
prove true, the glacial plain remains, and this cannot be Kansan. It is 
a youthful glacial plain and nothing of this type is found in any known 
Kansan drift-plain. 
Professor Shimek, in his recent article on the Sioux Falls region, 
speaking of the plain on the Dakota side states: “ There are few (en- 
tirely inclosed basins containing swamps and ponds.” 6 Attention has 
already been called to the presence of undrained depressions with 
swamps and ponds in the region north of Shindlar, and they are shown 
on thie accompanying map, figure 3. Farther west in township 100 
north, range 50 west, swamps occur in sections 11, 14, 15, 16, 21, 17 and 
7, and at several places in the south part of township 101 north, range 
50 west. These swamp areas are not extensive and the ponds are not 
large, but they are a common feature and their presence is significant 
as showing the recency of the plain. Continuing, Professor Shimek 
says, “the general character of the surface is very similar to that of 
the Kansan in O’Brien and Osceola counties in Iowa.’’ The Kansan 
plain of O’Brien county and southern Osceola county 63 - is in large part 
quite level, the relief being at many’ places no greater than that of the 
Dakota plain. But it is only in this matter of relief that the two regions 
should be compared. The relief features of a large part of the Dakota 
plain are independent of stream erosion. Narrow, sharply-cut val- 
leys have determined the relief features of a narrow belt on either side 
of them, but only a short distance back from these valleys the low 
rounded elevations and the shallow undrained depressions so character- 
istic of recent glacial plains, are the dominant features of the region. 
The relief features of the Kansan plain of O’Brien county consist of 
very broad shallow valleys. The courses of the valleys are usually di- 
rect and the drainage pattern is the usual dendritic type. Long gentle 
slopes lead down to the valleys from either side, and the divides are 
roundied. Although the relief may be slight all the surface has some 
slope and belongs definitely to some drainage basin. Along the stream 
courses are many marshy flood-plain areas but there are no depressions 
away from the stream courses. It is a region of very slight relief in 
6 Shimek, B., Pleistocene of Sioux Falls, South Dakota, and vicinity, Bull. Geol 
Soc. America, vol. 23, 1912, p. 149. 
