104 
IOWA ACADEMY OF SCIENCES. 
It will be seen from the above section that the exposure 
reveals two beds of drift which are separated from each 
other by an accumulation of vegetable material. Since 
this particular area is embraced within the region whose 
superficial till is of Kansan age, the age of the lower or 
older drift, number 1 of the section, can be safely referred 
to that of the pre-Kansan. 
The materials of this bed are dark blue in color with the 
exception of a zone about three feet in depth in the upper 
part. The superficial portion of this zone is iron-stained 
and is deep brown in color to a depth of two to four inches. 
Below this brown horizon the color changes to a light gray 
and this, in turn, passes with a gradual transition into the 
blue colored drift below. The constituents of this drift 
are calcareous to the very top of the bed. The clay shows 
nothing of the jointed structure that is a common feature 
of the beds of Kansan till. It contains numerous pebbles 
and small bowlders few of which exceed twelve inches in 
diameter. 
The second member of the section consists of narrow 
layers of quite pure peaty material intercalated between 
layers of sand. At the very base of this bed, and imme- 
diately overlying the iron-stained horizon of number 1, 
there is a layer of clean, fine-grained, light colored sand 
about four inches in thickness. This bed of sand is suc- 
ceeded by a layer of brown vegetable matter, three to four 
inches in depth, which in places is crowded with branches 
and splinters and fragments of wood. With these coarser 
wood-fragments are mingled masses of more or less com- 
minuted and disintegrated remains of vegetable matter. 
The entire thickness of the second member, above this 
basal layer of organic material, is made up of layers of 
fine-grained, light colored sand, which vary in thickness 
from two to four inches, alternating with brown colored 
layers of vegetable debris about equal in thickness with 
those of the sand. These layers of organic matter contain 
a surprisingly small admixture of sedimentary impurities. 
They are so compact that they stand out in conspicuous 
