BLUFF SECTIONS 1 o7 



2. Section four and one-half miles west of Fairview. — This section is 

 located in the bluff near the north line of section 18, township 97 north, 

 range 49 west. 



Kansan, 10 feet exposed. 

 Af tonian : 



Silt containing fragments of shells, about. 10 feet. 



Sand, about 15 feet. 



The base of the Af tonian appears to be about 75 feet above the river 

 bottom, but the lower part is slumped and the base could not be deter- 

 mined. Copious springs flow from the Aftonian along these bluffs. 



3. Beloit section. — This is located in section 19, northeast of Beloit, 

 Iowa, opposite Canton. It was formed b}^ a land-slide and shows the fol- 

 lowing members: 



Yellow loamy material, probabl}^ loess overwash, 5 feet. 

 Kansan drift, typical, with boulders, 27 feet exposed. 

 Aftonian sand, 13 feet. 



Nebraskan drift, rising 65 feet above the river, its upper 30 feet 

 clearly exposed. 



The Kansan and Aftonian are separated by a sharp, ferruginous line, 

 and the Aftonian has a layer of cemented sand, 2 inches thick, at its base. 

 The Nebraskan is typical blue-black till, with its uppermost 5 or 6 inches 

 very ferruginous. 



Aftonian and Nebraskan appear at other points between this section 

 and the bend of the river to the east. 



4. Section in the southwest quarter of section 33, township 99 north, Ci 

 range 48 west. — This section has been exposed by a land-slide, and is 

 located on the Iowa side of the Big Sioux. The north side of this ex- 

 posure shows : 



Kansan, 15 feet exposed, but Kansan boulders strew the hillside for 



85 feet above the section. 

 Aftonian, chiefly sand, with a few lines of pebbles, capped with 



about 2 feet of silt containing shells, 10 feet. 

 Nebraskan, typical blue-black till, with a large number of boulders, 



60 feet. 



This is the finest section of Nebraskan which has yet been discovered, 

 and the exposure is clear for fully 60 feet, its base disappearing in the 

 river. The Nebraskan here contains an unusually large number of boul- 

 ders and portions of it are coarsely jointed. This is probably what has 



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



