AN EXPOSURE SHOWING, POST-KANSAN GLACIATION 
NEAR IOWA CITY, IOWA 
MORRIS M. LEIGHTON 
University of Iowa 
While collecting field data pertaining to the Pleistocene history of 
Iowa River, in Johnson County, Iowa, the writer recently examined 
a railway cut which furnishes some striking evidence, additional 
to that already presented by the late Professor Calvin, that a post- 
Kansan ice-sheet, much younger than the Kansan, invaded this 
part of the state of Iowa. It was thought, while this paper was 
being prepared, that no previous study of this interesting cut had 
been made, but Professor Shimek states that he examined the 
exposure some years ago. 
The exposure is in a cut made in 1905 by the Cedar Rapids & 
Iowa City Interurban Railway. It is located } mile northwest of 
the upper Interurban bridge across Iowa River and about 15 miles 
by rail northwest of Iowa City. The railroad grade here runs 
through the south end of a divide projecting somewhat into Iowa 
River valley, the summit of the divide at the surface of the cut 
being about 30 feet above the valley flat. The physiographic 
setting is shown in Fig. 1. This is within the area mapped as 
Iowan drift by Calvin." 
The cut is about 250 yards long and attains a maximum depth 
of 20 feet. For about 120 yards, the east end is till, and for 100 
yards at the west end the material is yellow fossiliferous loess. 
Between these are contorted folds and rolls of Buchanan gravel in 
peculiar relation to the Kansan till below and overlain by 2 to 8 
feet of till. The arrangement of the materials is shown in Fig. 2. 
The oldest material in the cut is Kansan till—blue at the bottom 
and grading up in places into a grayish to yellow color according to 
the degree of weathering. The blue is very clayey, contains small 
pebbles, many of which are greenstone, and breaks with polyhedral 
t Samuel Calvin, Towa Geological Survey, VII, opposite p. 92. 
431 
