POST-KANSAN GLACIATION NEAR IOWA CITY 
fracture. Joints are preva- 
lent in the yellow clay and in 
the upper part of the blue, 
but instead of being vertical 
they dip toward the west, 
suggesting that they are the 
result of pressure from that 
direction. In that case they 
might be regarded as slight 
shear planes resulting from 
the same force that produced 
the distortion of the gravel 
above. Overlying this, in a 
peculiarly folded and con- 
torted manner, is Buchanan 
gravel, the textural range of 
which is from fine flour to 
bowlders 1 foot in diameter. 
The gravel exhibits the usual 
oxidized, weathered, and de- 
cayed character. Ironstones 
are not uncommon and 
cementation by iron oxide is 
sufficiently prevalent to have 
preserved stratification lines 
at many points. 
At the west end of this 
section (left end of Fig. 2), 
the gravel appears in a narrow 
band in the lower part and 
rises to the east at an angle 
of about 45 degrees, reaching 
a height of 16 feet. From 
this point the gravel follows 
a horizontal course eastward 
for about 75 feet and ends 
rather abruptly against till. 
433 
Fic. 2.—View of the north face of Interurban cut, 15 miles northwest of Iowa City, [owa, showing the arrangement of Buchanan 
The numerical index is referred to in the text. 
overlain by a later till. 
gravel on Kansan till and 
