254 
IOWA ACADEMY OF SCIENCE 
of a mile, with higher land to the north, as shown in Fig. 3, still 
further suggests a terrace. Were it not for the break in continuity by 
the tributary, the semblance would undoubtedly be even more perfect. 
In the bottom of the pit, are distinct pockets and lenses of gravel, 
sand, and some silt, with a range in texture from very fine to pebbles 
the size of a walnut. The outlines of the pockets depict well the courses 
of rapid currents, which afterward became filled with sand and gravel. 
About 4 feet higher the material grades into sand and silt. From the 
dominancy of sand the material grades upward until it becomes domi- 
nantly silt and finally loess, containing terrestrial molluscan shells. The 
material at the bottom is unquestionably a running water deposit, that 
at the top is clearly eolian, but no line between them can be drawn. 
However, at least ten feet of the bottom of the exposure is aqueous. 
Just how much lies below this is not shown. At present the deposit is 
separated from Iowa River by a “second-bottom” one-eighth of a mile 
wide, and by a vertical distance of 24 feet. The materials are hetero- 
geneous in composition, fresh, and unconsolidated. 
Inasmuch as the materials are of glacial character and similar to 
those in Pardieu Creek and other tributaries to Iowa River upstream, 
it seems best to refer them to the same origin. 
There are several other terraces along the course of the river between 
the one mentioned above and upstream to where the Iowan drift-area 
crosses the river, some of which are quite perfectly developed. One espe- 
cially deserving of mention occurs just above the Mehaffey bridge, in 
the southeast quarter of section 32, township 81 north, range 6 west. It 
is about 30 feet high, % m ^ e long, % mile wide at a maximum, and is 
backed by a distinct valley-wall 40 to 60 feet high. A well by the 
house on the east end of the terrace has the following log, as given by 
the digger: Depth 63 feet (dug 27 feet, drove 36 feet) ; yellow clay lfi 
feet, river-sand and gravel about 27 feet; hard-pan 20 feet. 
CONTORTED BUCHANAN GRAVEL. 
An excellent exposure of folded and contorted Buchanan gravel in 
intimate relations to weathered and unweathered Kansan and overlain 
by till, is shown in the first Interurban cut north of the upper Inter- 
urban bridge across Iowa River. 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. This is within the area mapped as Iowan Drift 
by Calvin. 
