WISCONSINAN MOLLUSCAN FAUNAS 29 



LAKE BLOOM INGTON SPILLWAY SECTION 



SWi NEi sec. 1, T. 25 N., R. 2 E., McLean County, Illinois, 1957, 1958, and 1959. 

 Adapted from earlier section by George E. Ekblaw 



Pleistocene Series Thickness 



Wisconsinan Stage (feet) 



Woodfordian Substage 

 Richland loess 



10. Loess, oxidized, leached, massive, buff. 3.0 



Normal till 



9. Till, clayey, massive, gray-tan, leached in uppermost 



part (P-148). 3.0 



8. Sand and gravel, calcareous, tan (P-147). 2.0 



Normal or Bloomington till 



7. Till, massive, pebbly, calcareous, pink-tan (P-146). 3.0 



Interstadial silt 



6. Silt with some sand, massive, weakly calcareous, streaked 



gray-tan and brown. 1.5 



Bloomington, Leroy, or Shelbyville till 



5. Till, massive, pebbly, calcareous, gray to blue-gray (P-145). 8.0 

 Farmdalian or Altonian Substage 



4. Silt, massive, compact, greenish gray to pink-gray with 

 some color banding (P-144); contains peaty zones and 

 streaks; lenticular; yielded C^ 4 date (W-67) greater 

 than 34,000 years (note conflicting date from bed l). 

 Yielded fossil snails (locality 24). 2.5 



Altonian Substage, or older 



3. Till, cobbly and gravelly, relatively loose locally in 

 lower part, in upper part more compact, calcareous, 

 oxidized at top (P-143). 3.0 



2. Till, compact, massive, pebbly, calcareous, gray (P-142). 5.0 

 1. Till, compact, massive, jointed, calcareous, pebbly, 



purplish-gray, upper 8 inches slightly less calcareous 

 than remainder of till (P-141); top marked by a pave- 

 ment of pebbles, cobbles, and boulders, all faceted, 

 polished, and striated along a planeate surface. Sample 

 of wood from till gave a C^ date of 31,000 or older 

 (W-186); to level of water in spillway channel. 8.0 



Total Pleistocene measured 39.0 



MASON COUNTY SECTION 



SEi NEi NWi sec. 36, T. 20 N., R. 7 W. , Mason County, Illinois; 



along north valley wall of Sangamon River Valley, 1959. 



Measured by John C. Frye, A. Byron Leonard, and H. B. Willman 



Pleistocene Series Thickness 



Wisconsinan Stage (feet) 



Woodfordian Substage 

 Peoria Loess 



5. Loess, gray and yellow-tan in indistinct zones, massive, 

 calcareous, medium coarse (P-577 base); fossil snails 

 in upper one-third below the soil profile (locality 28). 40.0 

 Altonian Substage 

 Roxana silt 



4. Loess, pink, massive, weakly calcareous, compact, non- 



fossilif erous (P-576). 4.0 



