IOWA ACADEMY OF SCIENCES. 
59 
and currently known as the Kansan, must be correlated with the 
upper till at Af ton Juncton. The Aftonian gravels were demon- 
strated to lie below the Kansan instead of above it, and the 
lower boulder clay at their type locality must be rechristened. 
Professor Chamberlin,* in an editorial on the series of glacial 
deposits in the Mississippi valley, designates the lower till at 
Afton by the term sub- Aftonian and suggests its probable 
equivalency with the Albertan of Dawson. 
This fortunate discovery and happy recognition of a sub- 
Aftoiiian drift sheet in south central Iowa naturally suggested 
its probable presence in other portions of the state. 
During the present autumn one and perhaps two sections in 
northeastern Iowa have been brought to light which afford 
additional evidence of a pre-Kansan ice sheet. 
Oelwein Section . — The cut on the Chicago Great Western 
railway, east of the town of Oelwein, in southern Fayette 
county, exhibits the following series of glacial deposits: 
5. Boulder clay, rather dull-yeilow in color; the upper portion 
is modified into a thin soil layer. Large boulders, mainly 
of the granitic type, are present, often resting on or par- 
tially imbedded in the deposits lower in the series. 
(Iowan) 0-10 feet. 
4. Sand and gravel— -not a continuous deposit; often shows 
water action expressed in parallel stratification lines and 
false bedding. The gravels are usually highly oxidized 
and fine textured. (Buchanan) 0-2 feet. 
3. Till, usually bright-yellow above, graduating into a gray- 
blue when dry or a dull-blue when wet, below. This 
deposit is massive and exhibits a tendency to joint when 
exposed. Decayed granitic boulders are common. (Kan- 
san) 3-20 feet. 
2. (a) Sand, fine-white, well water-worn; often with a slight 
admixture of silt and clay. (Aftonian) 0-6 inches. 
{b) Vegetal layer and soil, from two to four inches of almost 
pure carbonaceous matter, with one to three feet highly 
charged with humus. The peaty layer often affords 
specimens of moss (Hypnum) perfectly preserved. 
(Aftonian) 0-4 feet. 
1. Till, greenish-blue when wet or gray-blue with a greenish 
cast when dry. Greenstones and vein quartz pebbles 
predominate. (Sub- Aftonian or Albertan.) Exposed 10 feet. 
The Oelwein hill trends northwest and southeast and is 
bilobed. The divisions will be referred to in the present paper 
as east and west lobes. 
* Journal of Geology, vol. IV, No. 7, p. 873 et seq., 1896. 
