252 
IOWA ACADEMY OF SCIENCE 
former discussions. 
A discussion of this area has been partially entered into by Calvin. 
The contrast between the youthful topography of the North Liberty 
lobe and the mature topography of the bordering Kansan, together with 
the marginal deposits of loess bounding the lobes of the Iowan, are noted 
in Volume VII of the Iowa Geological Survey, pp. 39-46 and 83-87. 
Reference is also made in several of the county reports to terraces of 
Iowan gravel in the valley of Iowa River, but no location, description, 
or adequate' significance is pointed out concerning them. During the 
field-work of the present writer, some of these terraces, formerly unbe- 
known to him and perhaps the identical ones referred to by Calvin, were 
found. The typical ones of these will now be considered. 
VALLEY-TRAIN TERRACES. 
In valleys leading down from the North Liberty lobe and from the 
Shueyville lobe to Iowa River, and along Iowa River from Curtis to 
Iowa, City, are the following terraces of sand and .gravel : 
Pardieu Creek Terrace . — A notable terrace occurs on the west side of 
the valley of Pardieu Creek about one mile below the North Liberty lobe, 
in the west central part of section 29, township 80 north, range 6 west. 
The terrace is about % mile long, 15 feet high, and from 25 to 75 yards 
wide. Except where dissected it has a flat top, and is backed by a hill 
that rises 60 feet above the terrace. (See Fig. 2.) 
Several exposures in the side of the terrace show stratified sand and 
gravel, with a few small lenses. The sand is dominant, but gravel ranging 
in size up to three inches, is mixed with the sand. The material shows no 
alteration, and it is so loose that it will not stand with steep face. In 
every way it presents a fresh appearance. 
The deposition of the sand and gravel took place, it is clear, after Par- 
dieu Creek had cut its valley. Whether the deposition took place by 
drainage waters from the North Liberty lobe or from a wash into the 
valley from the west, the significance is the same. The material is of 
glacial origin, and the fact that Pardieu Creek was changed from an 
eroding stream to a depositing one for a, period sufficiently long to 
aggrade its bed 15 feet, together with the fact that it drains from the 
North Liberty lobe, indicates that Pardieu Creek was a drainage line 
from an ice-sheet after its valley was eroded. 
Two deposits, apparently of similar character, occur in other drain- 
age lines leading from the North Liberty lobe. One of these is in a 
