THE JULES SOIL AND ASSOCIATED MOLLUSCAN FAUNAS 



TABLE 1 — GRAIN SIZE AND CLAY-MINERAL COMPOSITION OF PEORIA 

 LOESS AT COTTONWOOD SCHOOL SOUTH SECTION 



Sample 

 no. 



Gravel* 

 (%) 



Matrix 



particle size 



(%) 



Clay minerals 

 (%) 



Sand* 



Silt 



Clay 



Expandable 

 clay minerals 



Illite 



Kaolinite 

 and chlorite 



P-7586 



2.2 



1.7 



90.8 



7.5 



29 



52 



19 



P-7585 



3.3 



0.6 



92.0 



7.4 



35 



47 



18 



P-7584 



0.7 



1.2 



91.1 



7.7 



32 



50 



18 



P-7583 



0.8 



0.4 



93.4 



6.2 



38 



45 



17 



P-7582 



0.0 



0.8 



93.5 



5.7 



34 



51 



15 



P-7581 



0.4 



1.3 



92.2 



6.5 



36 



46 



18 



P-7580 



3.1 



2.0 



83.2 



14.8 



60 



29 



11 



P-7579 



1.1 



1.5 



85.3 



13.2 



58 



30 



12 



P-7578 



0.4 



0.9 



89.2 



9.9 



56 



32 



12 



P-7577 



3.6 



1.0 



88.8 



10.2 



50 



36 



14 



P-7576 



1.5 



1.7 



87.6 



10.7 



53 



33 



14 



P-7575 



0.9 



1.0 



88.7 



10.3 



38 



47 



15 



P-7574 



0.5 



0.8 



91.2 



8.0 



31 



51 



18 



P-7573 



0.6 



0.3 



93.4 



6.3 



29 



53 



18 



P-7572 



0.6 



1.1 



90.7 



8.2 



33 



49 



18 



P-7571 



0.8 



1.3 



91.4 



7.3 



44 



39 



17 



'Mostly CaCO. concretions. 



increase in percentage of clay that is sharply terminated at the top of the Jules 

 Soil. The clay mineral composition (fig. land table 1) shows a sharp change 

 at both the top and bottom of the soil. Clay mineral data for the nearby Jules 

 Section have been published previously (Frye, Glass, and Willman, 1968) and 

 show similar relationships. 



In order to show the extreme situation that locally occurs at the bluff 

 line in exceptionally thick, coarse-textured Peoria Loess, we sampled the Jules 

 Soil interval at the Bunkum South Section, SEiNWiNEi sec . 24, T. 2 N. , R. 9 W. , 

 St. Clair County. The clay mineral data and the positions of A-horizons are 

 shown in figure 2. At this locality four A-horizons occur within a vertical dis- 

 tance of 9 feet and are separated by 1 to 2 1/2 feet of loess that superficially 

 resembles the deposit above and below the soil zone. Although the sequence 

 is much thicker and the deposits are coarser textured, the relationship of the 

 clay mineral assemblages strikingly parallels that shown at the Cottonwood 

 School South Section (figs. 1 and 2). 



