THE SANGAMON SOIL AND WEATHEEED ZONE. 127 



in this railway cutting represents about the average depth found in the interior 

 portions of the district covered by the Illinoian drift. Along the borders 

 of the drift, as previously noted, the Illinoian till is, in places, noncalcare- 

 ous throughout its entire depth, and seems to be made up largely of the 

 leached portion of the Kansan drift which it had overridden. Some care 

 must be exercised, therefore, in deciding upon the amount of leaching which 

 has taken place since the Illinoian ice sheet disappeared. 



In northern Cumberland County, Illinois, a short distance north of 

 Greenup, Professor Chamberlin and the writer examined exposures of the 

 Sangamon soil in which branching rootdike extensions of the soil penetrate 

 several inches into the underlying subsoil. These are thought to mark the 

 former presence of forests on that soil. 



In a few places peat beds of considerable depth have been found at 

 this soil horizon. Some of the best instances occur a short distance west 

 of the region in which the section reported by Worthen is found. The coal 

 shaft at Ashland, Illinois, near the line of Sangamon and Cass counties, 

 shows the following series of drift beds : 



Section of the drift beds in a coal shaft at Ashland, Illinois. 



Feet. 



Black soil 1£ 



Loess of yellow color 



Loess of blue color 2 



Peat and black sandy slush 22 



Bluish gummy clay 20 



Yellow till 30 



Total drift 85 



At the air shaft sand was found beneath the peat in the place of the 

 blue gummy clay. At Virginia, Illinois, a well made by Mr. Oldridge 

 entered a bed of peat at the base of the loess at about 1 5 feet g„nd continued 

 in it to a depth of 28 feet, beneath which a blue clay was entered. 



An instance of the occurrence of animal remains in the basal portion 

 of the loess, immediately above a deposit of peat, probably Sangamon, was 

 long since brought to notice by Mr. Pratt, of Davenport. 1 In a railway 

 cutting made by the Chicago, Rock Island and Pacific Company, in the 



1 Proc. Davenport Acad. Sci., 1876, p. 96, PI. XXXII. See also Geol. of Iowa, by C. A. White, 

 Vol. 1, 1870, p. 119. 



