62 
IOWA ACADEMY OF SCIENCES. 
exposure. Granitic pebbles and boulders are, almost if not 
entirely, wanting. The pebbles in this as in the Kansan often 
exhibit polished, striated and facetted surfaces. The sub- 
Aftonian shows oxidation only where the superficial deposits 
are thin and the indications are that such oxidation took place 
after the deposition of the Kansan. At the extreme east end 
of the cut, beyond the peat-bed, there is an apparent exception 
to this rule. Blue till boulders of the Kansan are imbedded in 
an oxidized matrix of the basal drift sheet. 
Albion Section , — Another section has come to the writer’s 
notice during the past year which bears additional testimony 
to a drift sheet older than the Kansan. At the Albion mills on 
the Iowa river about ten miles northwest of Marshalltown, the 
following series of deposits may be observed: 
6. Loess, stratified sands below 20 feet. 
5. Till, yellow in some places apparently wanting and often rep- 
resented by characteristic boulders, only. (Iowan) 0-1 foot 
4. Gravel, some boulders four or five inches in diameter; granitic 
members often much decayed; limestone pebbles are common 
and boulders of Kansan till decorated with pebbles were 
noted. (Buchanan) 2 feet. 
3. Till, the upper portion highly oxidized to a deep reddish- 
brown, unoxidized portion a gray-blue, exhibiting a jointed 
structure. (Kansan) 4 feet. 
2. Sands and gravels, stratified and coarser below; oxidized in 
streaks, and bands approximately parallel to bedding planes; 
certain bands contain a considerable percentage of silt and 
clay. (Aftonian) 10 feet. 
1. Till, blue. (Sub- Aftonian).. 10 feet. 
The Kansan at this point is more highly oxidized than at 
Oelwein, while the gravels between the Iowan and Kansan are 
very sharply defined. 
The Aftonian does not present the iron- stained appearance 
usual to such deposits. Many of the pebbles and boulders are, 
however, in an advanced stage of decay. 
EXPLANATION OP PLATES. 
Plate II. The Oelwein Section. 
1. Sub- Aftonian. 
2. Aftonian. 
3. Kansan, composed of an upper oxidized and a lower unoxidized 
portion. 
5. Iowan. 
Plate III. The Albion Section. 
2. Stratified sands and gravels of the Aftonian. 
3. Kansan till oxidized in part. 
4. Buchanan, consisting of coarse gravel. 
6. Loess, with stratified sands and silts below. 
