12 



■All. MAC CLINTOCK 



DESCRIPTIVE NOTES 



8. The post-Illinoian loess is the typical light-buff, fine-textured loess of the 

 southern part of the state. 



7. Illinoian gumbotil is the typical dark bluish-gray, sticky, leached, and 

 highly weathered surface of the Illinoian till. 



6. The leached Illinoian till is fairly dense, dark yellow-brown, and stony, 

 from which the lime content has been so removed by downward moving water 

 that it does not effervesce with acid. Sand and gravel, also leached, are incor- 

 porated as lenses and pockets in the till. 



5. In the northern part of the exposure (Sec. 2) the leached till grades 

 almost imperceptibly downward into calcareous till, from which the lime carbonate 

 has not yet been removed. This calcareous till is darker in color and somewhat 

 more dense than the overlying drift. It shows also the fracture and texture of 

 fresh till. At its base in one place 4 inches of sand and small pebbles have been 

 cemented by lime into a fairly well-indurated conglomerate. In the southern part 

 of the exposure (Sec. 1) the Illinoian till with the incorporated sand and gravel 

 is leached to its base. 



4. The 12-15-foot layer of dark brownish-gray loessial silt is entirely leached. 

 Uniform in texture and composition from bottom to top, it fractures with char- 

 acteristic loess faces and columns. 



^-^— — "^ 



"~- 2 



. — — — ^7> '•'.' • 



iiuiuuuiUt!iu>umtjiir^ - , — : ~ 



./• 





-.:-------' - '-r';-. ■-- '---■ f °~ 





<- I.oess 

 *- Gumbotil 

 <r-Lchd. till 

 <nCalc. till 



<-Lchd. Loess 



<- Gumbotil 

 <-Lchd. till 

 «-Calc. till 



Fig. 3. — Diagram of the Schuline cut 

 Scale: Vi inch = 10 feet 



3. In the northern part of the cut (Sec. 2) the leached loess lies on a 3-foot 

 horizon of brown-mottled, blue-gray dense, sticky gumbotil. While not as well 

 developed as the Illinoian gumbotil in this cut, it is nevertheless a very old - 

 zone and represents a long interval of weathering. In the southern part of the 

 cut (Sec. 1) the gumbotil was eroded away before the loess (No. 4) was deposii' 



2. The leached till is entirely oxidized to a yellow-brown color. It is fairly 

 hard and medium stony. Stones up to 3 inches are not uncommon. 



1. The calcareous till at the base of the cut is notable because of its hardm 

 compactness, and durability. The sharp pick must be driven with considerable 

 force to dig into it. The mass is entirely oxidized to a yellow-brownish color, 

 which is more pronounced along the many joints traversing it (Fig. 4). In the 

 joints themselves, however, gray deoxidized color is seen. Along these joints, 

 also, secondary lime has been deposited to so great an extent that erosion has left 

 the joint filling projecting bsyond the general surface (Fig. 4). 



The lower till contains not only many small polished and striated lime- 

 stone pebbles, but also numerous cobbles and a few bowlders ranging in 

 diameter up to a foot and a half. Sand and gravel lenses are also present) 

 No purple quartzites were seen. A pebble count gives the percentage of 



