CERAMICS OF GUMBO SOILS 
405 
patches. Topographically the gumbo soils have very definite re¬ 
lations. The circumstance that in southern Iowa gumbo rests on 
the oldest till sheet is, therefore, not in any sense a genetic rela¬ 
tionship. When wider prospect is taken, gumbo is discovered not 
to be restricted to the surfaces of the oldest drifts. Gumbo is 
found not only not confined to this till, but reposed upon alluvium, 
loess, and even sands. It occurs in full force far outside of the 
limits of glaciation, and among residual soils that glacier never 
touched. In the continental interior gumbo is as common on the 
Mexican border as it is in southern Iowa. 
From the viewpoint of the clay-worker gumbo is a typical silt. 
Calvin’s title of “blue soil” expresses the essential qualities as recog¬ 
nized in ceramics. This name also indicates its real genesis. It 
is, indeed, a water-formed product, although perhaps not always a 
true sedimental deposit. It is not all a formation of the long, long 
ago. To the contrary it is actually being formed today abundantly 
on the bottom lands of nearly every stream, where during times of 
flood the waters are highly charged with fine mud in suspension. 
Wherever the current slackens or the waters spread out over the 
lowlands the settling silt forms as typical gumbo as may be found 
anywhere. Gumbo is often a direct product of muddy waters. It , 
is known to form over night. In direct opposition to the claim of 
Kay and Pearce that gumbo is an index to the relative antiquity 
of the Glacial tills it is more properly indicative to its formation 
only yesterday. 
The same is true of the uplands. Whenever the drainage is 
^poor gumbo forms. It is especially in evidence in the prairie 
swales between hills. These spots are the' ones where unimproved 
highways are most impassible in wet weather. Like conditions pre¬ 
vail far beyond the bounds of the glaciated area. 
Whenever formed on alluvium the gumbo appears to pass into 
it by imperceptible gradations. Likewise, when it rests on till, 
or loess, it seems to be a part of the same. The intrinsic evidence 
is everywhere plain that gumbo is not developed in situ by ordinary 
normal weathering of subjacent clays. The gumbo materials are 
often clearly transported. The failure of McGee ^ to recognize in 
gumbo a true silt led him into fantastic speculation. Kay and 
2 Eleventh Ann. Rept. U. S. Geol. Surv,, pt. x, p. 509, 1891. 
