I ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 486 



A-horizons merge into a single A-horizon only 1 to 2 feet thick, the thickness 

 of loess above the soil thins sharply, and the texture of the loess becomes finer 

 grained. The type section of the Jules Soil is in such a situation. 



Exposures in roadcuts at the Cottonwood School South Section, 1 mile 

 west of the Jules Section in Cass County, Illinois, afforded an especially good 

 opportunity to study this buried soil, including its age by radiocarbon dating; 

 the molluscan faunas above and below the soil; and the clay mineral composition 

 of the deposits. The Cottonwood School Section had been studied in some detail 

 (Willman and Frye, 1970); the Cottonwood School South Section occurs in a road- 

 cut immediately south of this classic section. A description of the Cottonwood 

 School South Section follows. 



Cottonwood School South Section 



Cottonwood School South Section, measured in roadcuts in NW^NW^SW^; 

 sec. 12, T. 18 N., R. 11 W. , Cass County, Illinois (1972). 



(Sample numbers preceded by "P" are the numbers used in the Illinois 

 State Geological Survey collection of lithologic samples.) 



Thickness 

 (feet) 

 Pleistocene Series 

 Wisconsinan Stage 



Woodfordian Substage 

 Peoria Loess 



6. Loess, coarse; contains Modern Soil in top; calcareous in 

 lower part; the gray to gray-tan A-horizon of the surface 

 solum is granular and friable; the light tan-brown B- 

 horizon has weak textural contrast and indistinct structure . 6.0 



5. Loess, coarse, calcareous, massive, fossilif erous, gray to 

 gray-tan; radiocarbon date on snail shells 10,410 ± 650 

 (ISGS-138). Samples: P-7586, h foot below top; P-7585, 

 middle; P-7584, h foot above base 2.0 



4. Loess, massive, calcareous, gray, highly fossilif erous; 

 radiocarbon date on snail shells 15,640+580 (ISGS-137) . 

 Samples: P-7583, top; P-7582, h foot above base; P-7581, 

 base 1.0 



3. Jules Soil (A-horizon), silt with some clay; dark gray- 

 brown in upper part becoming lighter tan-brown in lower 

 part; granular to massive, weakly calcareous, less friable 

 than bed above; generally lacks snail shells but contains 

 rare examples of Suaoinea sp. and some small nodules of 

 CaC0 3 . Radiocarbon date on humus 12,740+210 (ISGS-195) ; 

 date on humus from Jules Soil at the type section, 1 mile 

 to the east of this section, 15,020 ±300 (ISGS-179) . 

 Samples: P-7580, top; P-7579, h foot below top; P-7578, 

 1 foot below top 1.2 



2. Loess (C-horizon of Jules Soil), medium, massive, calcar- 

 eous, fossilif erous, gray to tan-gray; contains nodules of 

 CaC03 up to h. inch in diameter. Radiocarbon date on outer 

 one-third of nodules, 5,030 ±100 (ISGS-139A) ; on middle 

 one-third of nodules, 5,867 ± 80 (ISGS-139B) ; on inner one- 

 third of nodules, 7,370±140 (ISGS-139C). Samples: P-7577, 

 top h foot; P-7576, \ foot below top 0.8 



1. Loess, medium, massive, calcareous, friable; contains 



sparsely distributed snail shells; gray, with some streaks 



of light brown; slumped in lower part. Samples: P-7575, 



h foot below top; P-7574, 1 foot below top; P-7573, lh 



feet below top; P-7572, 2 feet below top; P-7571, 2% feet 



below top. To level of road grade 6.0 



Total 17.0 



