r.Q 



LOESS 15.- 



altitudes. The similar sand, gravel, and silt deposits which overlie the 

 Kansan at East Sioux Falls may have been produced by overflow waters 

 cutting across from the Sioux Falls lake to East Sioux Falls. 



The facts here presented warrant the conclusion that the gravels of 

 the terraces are related to the Kansan. They are not Wisconsin, for they 

 can not be traced back to a Wisconsin source, and no Wisconsin was found 

 in the area under discussion. 



The loesses. — While very distinct, the two loesses do not attain great 

 thickness, for they seldom reach a total depth of 10 feet in this region. 



The small amount of loess is probably due to the absence of streams 

 with broad beds and numerous bars, from which the wind could carry 

 dust. Probably a large part of the upper or yellow loess was carried from 

 the distant Missouri. 



They cover the hills opposite Canton and northward, and also the up- 

 lands in the great bend of the Big Sioux both east and southwest of Sioux 

 Falls and the uplands west of Fairview. Sometimes the lower loess is 

 missing, and less frequently the upper is not present, but in the rougher 

 areas both frequently appear in the same sections. 



Fossils are very rare in the loesses of this territory, possibly because 

 the accumulation of the loess has been so slow that the shells disintegrated 

 before they were completely buried. MoUusks now live in the region in 

 timbered areas and have probably existed here for a long time. 



Among the exposures showing two loesses the following may be men- 

 tioned : 



On the north side of the northeast quarter of section 2, township 98 

 north, range 48 west, showing Kansan and both loesses. 



On the north side of section 14, township 98 north, range 48 west, 

 both loesses and Kansan appear in normal relative position. 



Numerous sections appear along the road between the last section and 

 the river, and other portions of the uplands east of Canton show similar 

 sections. 



In the southeast quarter of section 13, township 97 north, range 49 

 west, two loesses lying on Kansan drift are exposed in four sections on 

 the south side and two on the east side of the quarter section, and several 

 exposures along the road between this point and Fairview show the same 

 formations. 



Near the southeast corner of the southwest quarter of the southwest 

 quarter of section 19, township 101 north, range 48 west, Kansan drift, 

 bluish loess, and yellow loess appear in a cut along the road, and other 

 portions of the uplands east of Sioux Falls show the same formations. 

 It is evident that no Wisconsin drift occurs on these uplands. 

 XI — Bull. Geol. Soc. Am., Vol. 23, 1911 



