THE IOWAN DRIFT 585 



might wish; but where the Buchanan gravels intervene, the fact 

 that there is a drift younger than the Kansan and perfectly distinct 

 from it is as clearly indicated as that there are two drifts separated 

 by the Aftonian horizon. 



Leaving out, therefore, all the evidence from the multitudes of 

 well sections and all other natural or artificial exposures that do 

 not show the intervening aqueous deposits, a few of the scores of 

 points where a young till overlies super-Kansan gravels may be 



Fig. 2. — View in the same pit a few rods west of point shown in Fig. 1, taken while 

 work of excavation was in progress, showing the uneven line of contact between the old 

 gravels and the younger, overlying Iowan. The irregularity in the contact line may 

 be due to plowing or gouging by the Iowan ice. 



cited. The best-known of these is the old Illinois Central gravel 

 pit near Doris in Buchanan County, a point that has been fre- 

 quently mentioned. Here are gravel beds with a maximum thick- 

 ness of fifteen feet or more. The deposit furnished many hundreds of 

 carloads of railway ballast annually for a number of years. In the 

 central part of the pit the gravel was taken out down to the blue 

 Kansan till, and balls of the same blue till are included in the 

 deposit. At the east end of the excavation there are at least ten 

 feet of yellow till above the gravel, recording a later, newer stage 

 of glaciation. The thickness of the later deposit is variable, for it 



