24 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 304 



GEOLOGIC SECTIONS 



The locations of the 11 measured geologic sections presented here and of 

 four similar sections published in Circular 285 are shown on the map in figure 1. 

 The numbers enclosed in parentheses, for example (P-762), refer to samples collec- 

 ted for mineralogical study and will be described in a subsequent report. The 

 sections are arranged alphabetically by name. 



ALTON QUARRY SECTION 



SE-f SW?- NE-f sec. 10, T. 5 N., R. 10 W. , Madison County, Illinois; measured in 

 Mississippi Lime Company quarry, 1958. (Type locality of Altonian Substage). 

 Measured by John C. Frye and H. B. Willman 



Pleistocene Series Thickness 



Wisconsinan Stage (feet) 



Woodfordian Substage 

 Peoria loess 



9. Loess, coarse, massive, yellow-tan, weakly calcareous 



(P-20). 12.0 



Altonian Substage 

 Roxana silt 



8. Loess, coarse, massive, pinkish tan (P-21 ), gradational 



with yellow-tan above;weakly calcareous; fossil snails 



sparse (locality 54). 14.0 



7. Loess, massive, noncalcareous, non fossilif erous, medium 

 gray to gray-tan (P-22); sharply truncated at top and 

 a darker zone gradational at base. 5.0 



Illinoian Stage 



6. Silt, sand, and clay, massive, noncalcareous, reddish brown, 

 general appearance of colluvium (P-23). This zone is 

 entirely within the A- and B-horizons of a soil profile 

 7 feet thick that extends into the underlying unit. 2.0 



5. Till, massive, highly calcareous except the uppermost 5 feet 

 which is leached (P-24, 2 feet below top), relatively 

 fine-textured, blue-gray to dark gray (P-26, 10 feet below 

 top). A one-foot sand zone (P-25) occurs 8 feet below 

 the top; lowermost 10 feet contains distorted masses and 

 bands of gray silt, fragments of wood, and scattered 

 snail shells. 35.0 



4. Silt, massive, light gray at bottom grading upward to 

 dark gray, calcareous, fossilif erous, gradational at 

 base, stems and wood fragments in upper part, and at 

 top a thin clay slickenside zone suggesting glacial 

 override. 1.0 



3. Silt, loess or loess-like, massive, calcareous, yellow- 

 buff, limonite banding in upper part (P-27); contains 

 abundant fossil snails. 4.0 



2. Silt, loess or loess-like, massive, weakly calcareous, 



tan to yellowish buff, limonitic banding. 6.0 



1. Silt, very fine sand, and clay, thinly laminated, non- 

 calcareous, rusty brown to chocolate (P-28); rests on 

 Mississippian St. Louis Limestone at a low point on 

 the unconformable surface. 3.5 



Total Pleistocene 82.5 



