IOWA ACADEMY OF SCIENCE 
247 
California Junction, Iowa. These areas, therefore, give strong 
support to the aeolian hypothesis.* 
The other type occurs between the Kansan drift and loess, and 
may be found at various points in Iowa, Nebraska and Missouri. 
In the Kansan territory the drift is very generally covered with a 
more or less variable layer, seldom exceeding one or two feet in 
thickness. It is usually dark (generally blue or reddish-brown), 
very compact and almost impervious, with pebbles and coarse 
grains of sand in the lower portions, but the upper parts usually 
fine, and often grading into loess, the change being usually com- 
pleted within a few inches. It is the deposit which McGee in- 
cluded as the lowest member of the loess series, and which Udden 
designates as gumbo. 
It is also the same as the lowest of the three “loesses” reported 
by Wilcox at Red Oak, Iowa, to which Todd refers. Professor 
Todd states (p. 191 1. c.) that “Udden admits that ‘red clay or 
gumbo’ may be a loess,” but a reading of the references which he 
cites shows that Professor Udden simply suggested the possi- 
bility that gumbo may be in part old loess which has been modified 
by subsequent conditions, and that he does not consider it typical 
loess. 
An examination of a large number of sections of this kind 
has convinced the writer that the gumbo is not genetically the 
same as loess. The material is harder, more compact, being evi- 
dently chiefly a glacial “joint clay,” and almost invariably contains 
pebbles, usually more or less scattered, or coarse grains of sand, at 
least in its lower parts. So far as the writer’s observations show 
it is wholly devoid of fossils, and none have been reported from it. 
It often grades downward into true drift, and not infrequently 
upward into true loess. This latter transition usually occurs within 
a very short vertical distance, rarely more than from one to six 
inches. Occasionally the line between the gumbo and the loess 
is sharp but a slight intergradation is more common. 
In its texture and presence of occasional pebbles the transition 
part of gumbo often resembles somewhat the deposits which the 
writer has observed in somewhat swampy places on the Wisconsin 
drift area in northern Iowa, and probably represents an old post- 
Kansan soil, the first to be formed after the withdrawal of the ice- 
sheet, probably chiefly by water action. A similar slightly pebbly 
*This question will be discussed more fully by the writer in a paper on the “Loess of 
the Paha and River-ridges.” 
