THE IOWAN DRIFT 



587 



Many similar cases could be cited, but it surely is not necessary 

 to multiply arguments in support of a fact that is so perfectly 

 obvious as the existence of the Iowan drift (Figs. 1 and 2). There 

 is no sheet of till that has more distinctive characters, more definite 

 stratigraphic relations. A glacial deposit showing thicknesses of 

 4 feet, 10 feet, 22 feet, 30 feet, a deposit with distinctive bowlders 

 of enormous size, a deposit that is young, fresh, uneroded, and 

 separated from the Kansan by a weathered ferretto zone and pro- 

 foundly altered gravels, is certainly a very real and substantial 



Fig. 3. — View in the Doris gravel pit, showing undermined Iowan bowlders; 

 one is still perched on the brink of the excavation; the larger companion has fallen 

 into the pit. 



thing that may not be disposed of by referring to it as "only the 

 weathered surface of a drift," or by the use of such a qualifying 

 phrase as "so-called Iowan." 



That there are two gravel horizons in this region — one Aftonian, 

 the other Buchanan, one below the blue Kansan drift, the other 

 above it — is indicated by two wells near the northwest corner of 

 Section 22, Buffalo Township, Buchanan County. One of the 

 wells, 152 feet deep and ending in gravel (Aftonian) which lies 

 beneath the Kansan, furnishes a constant stream of water an inch 

 in diameter; the other, which is not flowing, is 25 feet deep and 

 ends in a bed of Buchanan gravel which overlies Kansan. 



