394 IOWA ACADEMY OF SCIENCE Vol. XXVI, 1919 



especially in the middle of the deposit, are more or less horizontal. 

 A lens and pocket structure is conspicuous throughout the exposure 

 in which occasionally leached mud or clay balls are found. 



Although but ten feet of the ash-colored drift is exposed, the 

 slope of the hill is covered by drift to a height from forty to fifty 

 feet above the section. The exposed portion of the till contains 

 limestone pebbles and is filled with many concretions. Higher up 

 the slope of the hill, the drift is leached. The entire outcrop is from 

 150 to 250 feet long. 



The other section differs but little from the one just described, 

 except that it contains less gravel and no drift is exposed beneath 

 the sands. However, it contains near the base several thin leached 

 layers of till from one to two feet thick. Here and there, a well 

 weathered limestone pebble occurs in it, nor are lime concretions 

 entirely wanting. 



On the whole, the stratification of the sands and gravels of the 

 exposure in Louisa county is more horizontal than that of the one 

 .in Washington county. Barometric readings show that the two sec- 

 tions lie approximately at the same elevation : namely, from 620 to 

 630 feet above sea level. The length of the second outcrop is the 

 same as that of the first and the exposure is forty feet high. 



INTERPRETATIONS OF THE DEPOSITS. 



The deposits above described may be interpreted in either of the 

 following ways : 



1. The sand and gravel deposits are inclusions incorporated in 

 the Kansan drift. 



2. The sands and gravels are interbedded outwash material be- 

 tween two drifts which are of the same age and therefore Kansan as 

 the uppermost till is known to be of Kansan age. 



3. The sand and gravel deposits lie between drifts of two 

 different ages, the gravels and sands having been deposited in 

 connection with the lower till, but having been weathered during 

 interglacial times or before the deposition of the upper drift. 



VIEW 1. 



The sand and gravel deposits are inclusions incorporated in the 

 Kansan drift. 



Discussion. — Sand and gravel pockets incorporated in tills are 

 familiar to all. But whether large stratified inclusions of leached 

 and oxidized sands and gravels in fresh drift are common is very 



