KANSAX DRIFT ON SUB-AFTOXIAX 



137 



Pebble counts from the unleached portions of both tills yielded 

 the following results : 



Kind 



Kans \n 



Tin. 



Per Cen'j 



SUB-A] IONIAN 



Tu i. 

 Per Cent 



Greenstone and Dolerite. 



Limestone 



Granite 



Chert 



Quartzite 



Schist 



Quartz 



Volcanic Porphyry 



46 

 30 

 8 

 4 

 6 

 4 

 2 

 



42 

 28 

 6 

 8 

 6 

 2 

 2 

 6 



100 



100 



Interpretation: — In this exposure, which is one-half mile from 

 the former, the existence of the non-calcareous silts, containing 

 carbonaceous material, between the calcareous till above and the 

 leached and calcareous till below, makes it obvious that here 

 there are also two till-bodies of different age. Inasmuch as this 

 general region is one of mature erosion, as mentioned in the 

 former case, the upper till is believed to be Kansan till, the silts 

 Aftonian, and the lower till sub-Aftonian. The relations of 

 the loess to the Kansan till in this cut do not clearly show an 

 interval between their dates of deposition, but in view of the re- 

 lations in the cut first described and of the mantling nature of 

 the loess, it is probable that the rate of leaching of the Kansan 

 till was at least equaled by erosion and consequently no leached 

 zone remains. The lithology of the two tills, according to the 

 pebble count, does not show any marked difference. 



3. Farther east, about six miles east of Delmar Junction and 

 one mile northeast of Riggs, a Chicago. Milwaukee and St. Pan! 

 Railway cut, trending north 30° east, fifty to sixty feel deep, 

 and two hundred yards long, exposes two bodies of till, sep- 

 arated by a body of gravel. By referring to figure 14, B, the 

 relations of the materials, which are described below, will be 

 clear. 



F\ E I 

 7. Loess, soil-layer at the top 1 ft. thick, brownish 

 yellow and non-calcareous down to the till, snail 

 shells only in the calcareous portion; maximum 

 thickness 30± 



6. Ferretto zone of till, reddish brown, ahsent on lower 



slopes 0- 1 ' j 



