140 B. SHIMEK PLEISTOCENE OF SIOUX FALLS AND VICINITY 



Eock Island and Pacific Eailway bridge west of Granite, at points where 

 the river comes in contact with the bluffs, causing a slumping. They are 

 of special interest because they are located near or on the side of the 

 ridge which has been referred to the Altamont moraine, and show its 

 structure. All show typical Kansan above, which was also traced to the 

 summit of the ridge, and the southernmost, the first north of the railway 

 bridge, shows a band of sand near the base resting on a stratum which 

 appears to be N'ebraskan. 



The most interesting section in this series is located at the base of the 

 northward extension of this ridge at the Louis Egge house, opposite and 

 just south of the Iowa State line. Below this point ledges of Sioux 

 quartzite rise fully -10 feet above the river valley. Between the house and 

 these ledges numerous springs flow from beneath the Kansan drift-covered 

 slopes. A fine section, marked on the map, is exposed on the south side 

 of the small creek a few rods west from the slopes of the main bluffs 

 facing the river. It presents the following members : 



Kansan drift, typical, bluish, calcareous ; 6 feet exposed, but appear- 

 ing at greater elevations on the slopes above. 



Silt, grayish and ferruginous, 8 to 12 inches. 



Coarse sand, cross-bedded, water-bearing, more or less slumped, 7 

 feet. 



A very dark bed of heavy, tough material appears in the bed of the 

 creek at the base of the section. This is probably Xebraskan 

 drift. 



The silt and sand are evidently Aftonian, and the entire section closely 

 resembles some of the clearest sections along the Big Sioux and Mis- 

 souri rivers in both structure and relative position of the members. 



Another bluff section which is worthy of note in this connection lies to 

 the south of our territory, but belongs to the series of exposures which 

 may be traced to and along the bluffs of the Missouri Eiver. It is 

 known as : 



12. Otis miU-site section. — This section is located in the bluffs on the 

 west side of the Big Sioux Eiver opposite Chatsworth, Iowa. "\Miile it is 

 somewhat remote it belongs to this general region and has been discussed 

 by both Todd and Wilder. 



It shows a bed of dark fossiliferous silt resting on the Cretaceous; 

 above it is an irregular stratum of ferruginous gravel, and resting on 

 this is a thick bed of t3'pical Kansan drift covered with loess. 



Todd (1908) reports a lower jaw of a fossil horse and many fresh- 



