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Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume IV (1876-1877)

Chamberlin, T. C.
On the extent and significance of the Wisconsin Kettle moraine,   pp. [unnumbered]-234 PDF (11.1 MB)


Page 232


232     Wisconsin Academy of Sciences, Arts, and Letters.
stage of its activity, and separating the formations on either hand
by a chronological barrier. It is manifest that the true Boulder
Clay, or ground moraine, south of the belt, must have been formed
earlier than that north of it, and that the two portions are not at
all synchronous. In sedimentary formations synchronism is found
in horizontal strata, but in glacial deposits it is to be sought in
linear belts, concentric with the margin of the glacier. This fact
finds illustration, and emphasis, in the demarcation introduced by
this singular corrugation of the wide-spread glacial sheet. It is
difficult to limit the value of such a determinate line, in the midst
of the complex drift formations, if fully established, and should
similar belts be found to mark other stages of glaciation, there
would be opened a definite line of investigation that promises
much assistance in unraveling the gnarled skein of Quaternary
history.
  While it does not follow, necessarily, that all formations over-
laying the true glacial clay, south of the Kettle moraine, are older
than those occupying similar relations to the newer Till, north of
it, it is clear, that similarity of stratigraphical sequence is not, by
any means, sufficient ground for assuming chronological equiva-
lence. - It is evident, that all endeavors at correlation between the
superficial deposits, on the opposite sides of the moraine, should
be attempted with much circumspection.
  These suggestions have especial application to the discussion of
the vegetal deposits, so frequently found in the later Quaternary
formations. By many writers, the various deposits of this kind,
in the Mississippi basin, have been, very naturally, in the present
state of our knowledge, grouped together without reference to the
necessary discriminations above indicated, and, as a result, beds
of diverse age are referred to a common stratum. A general dis-
cussion of these deposits is not sufficiently germane to our sub-
ject to be fittingly introduced here, but it is appropriate to point
out the fact that some of the vegetal strata sustain such a relation
to the Kettle moraine, that they must be widely separated from
others, in the date of their accumulation and burial. Some of
these organic strata lie at the immediate foot of the moraine, be--
neath fluviatile and lacustrine deposits that, I am confident, began


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