University of Wisconsin Digital Collections
Link to University of Wisconsin Digital Collections
Link to University of Wisconsin Digital Collections
The State of Wisconsin Collection

Page View

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

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

Page 118

                                     CINCINNATI SHALES.
     A change ensued upon the formation of the Galena limestone, by virtue
of which there fol-
lowed the deposition of large quantities of clay, accompanied by some calcareous
material, the
whole reaching at some-points a thickness of more than 200 feet. The sediment
has never
become more than partially indurated, and a portion of it is now only a bed
of compact clay.
Other portions hardened to shale or limestone according to the material.
The shales are of
various gray, green, blue, purple and other hues, so that where vertical
cliffs are exposed, as along
Green bay, a beautiful appearance is presented. As a whole, this is a very
soft formation, and
hence easily eroded. Owing to this fact, along the east side of the Green-bay-Rock-river
ley, it has been extensively carried away, leaving the.hard overlying Niagara
limestone projecting
in the bold cliffs known as "The Ledge."  The prominence of the
mounds in the southwestern
part of the state are due to a like cause. Certain portions of this formation
abound in astonish-
ing numbers of well preserved fossils, among which corals, bryozoans, and
brachiopods, pre-
dominate, the first named being especially abundant. A little intelligent
attention to these might
have saved a considerable waste of time and means in an idle search for coal,
to which a slight
resemblance to some of the shales of the coal measures has led. This formation
underlies the
mounds of the lead region, and forms a narrow belt on the eastern margin
of the Green-bay-Rock-
river valley. This was the closing period of the Lower Silurian Age.
                                      CLINTON IRON ORE.
     On the surface of the shales just described, there were accumulated,
here and there, beds of pecu-
liar lenticular iron ore. It is probable that it was deposited in detached
basins, but the evidence
of this is not conclusive. In our own state, this is chiefly known as Iron
Ridge ore, from the
remarkable development it attains at that point. It is made up of little
concretions, which from
their size and color are fancied to resemble flax seed, and hence the name
" seed ore," or the
roe of fish, and hence oblitic ore. "Shot ore" is also a common
term. This is a soft ore occur-
ring in regular horizontal beds which are quarried with more ease than ordinary
limestone. This
deposit attains, at Iron Ridge, the unusual thickness of twenty-five feet,
and affords a readily
accessible supply of ore, adequate to all demands for a long time to come.
Similar, but much
less extensive beds, occur at Hartford, and near Depere, besides some feeble
deposits elsewhere.
Large quantities of ore from Iron Ridge have been shipped to various points
in this and neigh-
boring States for reduction, in addition to that sme'ted in the vicinity
of the mines.
                                     NIAGARA LIMESTONE.
     Following the period of iron deposit, there ensued the greatest limestone-forming
era in the
history of Wisconsin. During its progress a series of beds, summing up, at
their points of great-
est thickness, scarcely less th in eight hundred, feet, were laid down. The
process of formation
was essentially that already described, the accumulation- of the calcareous
secretions of marine
life. Toward the close of the period, reefs appeared, that closely resemble
the coral reefs of the
present seas, and doubtless have a similar history. Corals fo.m a very prominent
element in the
life of this period, and with them were associated great numbers of mollusks,
one of which
(Pentamerus oblangus)-sometimes occurs in beds not unlike certain bivalves
of to-day, and may
be said to have been the oyster of the Silurian seas. At certain points,
those wonderful animals,
the stone lilies (Crinoids), grew├Ż in remarkable abundance,, mounted
on stems like a plant, yet
true animals. Those unique crustaceans, the trilobites, wereconspicuous in
numbers and variety,
while-the gigantic cephalopods held sway over the life of the seas. In the
vicinity of th2 reefs,

Go up to Top of Page