THE ILLINOIAN ICE INVASION 289 



A caribou (Rangifer muscatinensis) was found by Mr. Witter in a deposit 

 thot to be loess. 13 Shimek (vide Hay, Geol. Iowa, XXIII, page 34) states 

 that the bones were in a deposit bearing the same relation to the Illinoian 

 drift that the Loveland bears to the Kansan drift, hence preceding the forma- 

 tion of the post-Illinoian loess. A fragment of an antler of a caribou was also 

 said to have been found by Prof. Witter, in the loess at Neibert's brickyard, 

 near Woodlawn and Orange streets, Muscatine. 



A tooth of Manumit americanum was secured from the bank of Mad Creek, 

 about a mile from its point of entrance to the Mississippi River. The tooth 

 was found about 10 feet beneath the surface of the bluff in a bed of gravel. 

 The deposit appears referable to the Sangamon. 14 



2. ILLINOIS 



The Sangamon horizon is widely distributed in southern, western and north- 

 western Illinois, and old soil or weathered strata have been found in almost 

 every county. In northwestern Illinois, the lowan was at one time thot to 

 overlie the Illinoian drift, 15 but later investigations 16 have shown that the older 

 drift is all referable to the Illinoian drift sheet. A typical section showing 

 post-Illinoian deposits is afforded by a coal shaft at Ashland, near the line of 

 Sangamon and Cass Counties. 



Black soil 1}^ feet 



Loess of yellow color (lowan loess) 9 " 



Loess of blue color (Illinoian loess) 2 " 



Peat and black sandy slush (Sangamon) 22 " 



Bluish gummy clay 20 " 



Yellow till (Illinoian) 30 



Height of section 84J^ feet 



a. Deposits of Fluviatile Origin 



Five miles south of Milan, Rock Island County, a deposit occurs at the 

 base of the loess in the bluff of Mill Creek. The fauna is almost exclusively 

 aquatic. 17 



Succinea avara Planorbis parvus 



Lymnaa stagnalis appressa? (fragment) Valvata tricarinata 



Galba reflexa " sincera 



Planorbis albus Pisidium species (fragments) 



"Leidy, Amer. Journ. Sci., (iii), XVH, p. 410; Hay, Geol. Iowa, XX111, pp. 34, 279. 

 u Witter, Proc. Iowa Acad. Sci., I, part 2, p. 67 ; Udden, Iowa Geol. Surv., IX, p. 352 . 

 u Leverett, Illinois Glacial Lobe, Chapter Vll. 

 u Alden, Journ. Geol., XVII, p. 694. 

 17 Leverett, Illinois Glacial Lobe, p. 174. 



