THE WISCONSIN DRIFT-PLAIN IN THE REGION ABOUT 
SIOUX FALLS. 1 
BY J. ERNEST CARMAN. 
The region considered 1 in this paper is a small area lying to the south 
and southeast of Sioux Falls, South Dakota, and the problem is, the 
age of a drift-plain. 
In 1883, Professor Chamberlin, in his paper on the Terminal Mor- 
aines of the Second Glacial Epoch, 2 outlined the extent of, and described 
the moraines of, the Minnesota-Des Moines valley glacier which extended 
southward through north central Iowa to the city of Des Moines, and 
the Dakota Valley glacier which occupied the James River drainage- 
basin in the eastern part of South Dakota and reached to the southeast 
corner of that state (Fig. 1). Professor Chamberlin traced the moraine- 
on the east side of the Dakota lobe southward to a point in northwestern 
Lincoln county, southwest of Sioux Falls, and then (p. 395) attributing 
the data to Professor Todd, he states that* it “bears eastward to the 
vicinity of the Big Sioux River, and thence follows the hilly tract bor- 
dering its west side southward into Union County.” 
In 1896, Professor Todd, in bulletin 14.4 of the U. S. Geol. Survey, 
mapped a belt of morainic surface, which, leaving the Big Sioux valley 
opposite the Iowa state line, runs west along the Minnehaha, -Lincoln 
county line and then northwest across the southwest corner of Minne- 
haha county. It is shown by the dotted area on figure 2. In bulletin 
158 (1899), of the same series, Professor Todd showed the morainic belt 
as on the earlier map and described (p. 35) “ a high massive ridge”' 
as beginning on the west side of the Big Sioux, a mile north of the Iowa- 
Minnesota state line and running west along the course shown on figure 2. 
This ridge was interpreted as the northeast boundary of the Dakota lobe.* 
of the Wisconsin drift-plain. The area to the northeast, including Sioux 
Falls and beyond, lies between the Dakota and 1 Des Moines lobes. The 
maps of Professor Todd show also two patches of morainic surface north- 
1 Published by permission of the Director of the Iowa Geological Survey. 
2 Chamberlin, T. C., Preliminary Paper on the Terminal Moraines of the Second 
Glacial Epoch, Third Annual Kept. U. S. Geol. Survey, 1883, pp. 291-402. 
