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The history of Columbia County, Wisconsin, containing an account of its settlement, growth, development and resources; an extensive and minute sketch of its cities, towns and villages--their improvements, industries, manufactories, churches, schools and societies; its war record, biographical sketches, portraits of prominent men and early settlers; the whole preceded by a history of Wisconsin, statistics of the state, and an abstract of its laws and constitution and of the constitution of the United States
(1880)

Chamberlin, T. C.
Topography and geology,   pp. [110]-120 PDF (5.3 MB)


Page 113


TOPOGRAPHY AND GEOLOGY
mud and sand, as at the present day, and we have before us the first authentic
stage of the history
under consideration. Back of that, the history is lost in the mists of geologic
antiquity. The
thickness of the sediments that accumulated in that early periodwaslmeiiiriiine&,
biingm..easured
by th      ds--o-ff   Te-eet.  - -n  occupied of course an essentially horizontalp.ositionand
were,   t- ie  n a large degree hardened -nto---eof impure sandstone, shale,
and other sedi.
mentary fork  t     inthe pfogress of time an enormous pressure, attended
by heat, was brought
to-ear upon them laterally, or edgewise, by which they were folded and crumpled,
and forced
up out of the water, giving rise to an island, the nucleus of Wisconsin.
The force which pro,
duced this upheaval is believed to have arisen from the cooling and consequent
contraction of
the globe. The foldings may be imaged as the "rinkles of a shrinking
earth. But the contor-
tion of the beds was a scarcely more wonderful result than the change in
the character of the
rock which seems to have taken place simultaneously with the folding, indeed,
as the result of the
heat and pressure attending it. The sediments, that seem to haveprevioiusly
taken the form of
impure sandstone and shale fo.rthe most part,..underw ent achange, in which
re-arrangement and
crystalization of theingr edi ents .p!ay ed a c n._spicucuous-.part. Byt--his
mietanionphism, granjt,ý gneiss,
mica schist, syen it e, hJornblenderoucks, chloritic schists-and-other- crystalline
rocks were formed.,
These constitute the Laurentian formation and belong to the most ancient
period yet distinctl
recognz     ne~~o        hyeugthewere undoubtedly more.ancient rocks. They
are therefore
Tiffitting1y termed Archliean-ancient-rocks (formerly Azoic.)  No remains
of life have been
found in this formation in Wisconsin, but from the nature of rocks elsewhere,
believed to be of the
same age, it is probable that the lowest forms of life existed at this time.
It is not strange that
the great changes through which the rocks have passed should have so nearly
obliterated all
"traces of them. The original extent of this Laurentian island. can
not now be accurately ascer-
tained, but it will be sufficiently near the truth for our present purposes
to consider the formation
as 4t is now exposed, and as it is represented on the maps of the geological
survey, as showing
app0roximately the original extent. This will make it include a large area
in the north-central
portion of the state and a portion of the Upper Peninsula of Michigan. All
the rest of the state
was beneath the ocean, and the same may be .said of the greater portion of
the United States
The height of this island was doubtless considerable, as it has since been
very much cut down by
denuding agencies. The strata, as now exposed, mostly stand in highly inclined
attitudes and
present their worn edges to view. The tops of the folds, of which they are
the remnants, seem
to have been cut away, and we have the nearly veitical sides remaining.
                                      HURONIAN PERIOD.
     As soon as the Laurentian island had been elevated, the waves of the
almost shoreless
ocean began to beat against it, the elements to disintegrate it, and the
rains of the then tropical
climate to wash it; and the sand, clay and other debris, thus formed, were
deposited beneath the
waters around its base, giving rise to a new sedimentary formation. There
is no evidence that
there was any vegetation on the island: the air and water were, doubtless,
heavily charged with
carbonic acid, an efficient agent of disintegration: the climate was warm
and doubtless very
moist - circumstances which combined to hasten the erosion of the island
and increase the
deposition in the surrounding sea. In addition to these agencies, we judge
from the large amount
of carbonaceous matter contained in some of the beds, that there must have
been an abundance
of marine vegetation, and, from the limestone beds that accumulated, it is
probable that there
was marine animal life also, since in later ages that was the chief source
of limestone strata.
The joint accumulations from these several sources gave rise to a series
of shales, sandstones
and limestones, whose combined thickness was several thousand feet.
113


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