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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

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

Page 119

there seem to have been extensive calcareous sand flats and areas over which
fine calcareous mud
settled, the former resulting in a pure granular dolomite, the latter in
a compact close-textured
stone. The rock of the reefs is of very irregular structure. Of other portions
of the formation,
some are coarse heavy beds, some fine, even-bedded, close-grained layers,
and.some, again, irregu-
lar, impure and cherty. All are highly magnesian, and some are among the
purest dolomites
known. The Niagara limestone occupies a broad belt lying adjacent to Lake
                               LOWER HELDERBERG LIMESTONE.
     On Mud creek, near Milwaukee, there is found a thin-bedded slaty limestone,
that is
 believed to represent this period. It has neglected, howe.ver, to leave
us an unequivocal record
 of its history, as fossils are extremely rare, and its stratigraphical relations
and lithographical
 character are capable of more than one interpretation. Near the village
of Waubeka in
 Ozaukee county, there is a similar formation, somewhat more fossiliferous,
that seems to repre-
 sent the same period. The area which these occupy is very small and they
play a most insignifi-
 cant part in the geology of the state. They close the record of the Silurian
age in Wisconsin.
 During its progress the land had been gradually emerging from the ocean
and increasing its
 amplitude by concentric belts of limestone, sandstone and shale. There had-been
no general
 disturbance, only those slight oscillations which changed the nature of
the forming rock and
 facilitated deposition. At its close the waters retired from the borders
of the state, and an
 interval supervened, during which no additions are known to have been made
to its substructure.
                                      DEVONIAN       AGE.
                                   HAMILTON CEMENT ROCK.
     After a lapse of time, during which the uppermost Silurian and the lowest
Devonian strata,
as found elsewhere, were formed, the waters again advanced slightly upon
the eastern margin of
the state and deposited a magnesian limestone mingled with silicious and
almuninous material,
forming a combination of which a portion has recently been shown to possess
properties of a high degree of excellence. With this deposition there dawned
a new era in the
life-history of Wisconsin. While multitudes of protozoans, radiates, mollusks
and articulates
swarmed in the previous seas, no trace of a vertebrate has been found. The
Hamil-ton period
witnessed the introduction of the highest type of the animal kingdom into
the Wisconsin series.
But even then only the lowest class was represented-the fishes. The lower
orders of life, as
before, were present, but the species were of the less ancient Devonian type.
Precisely how far
the deposit originally extended is not now known, as it has undoubtedly been
much reduced by
the eroding agencies that have acted upon it. That portion which remains,
occupies a limited
area on the lake shore immediately north of Milwaukee, extending inland half
a dozen miles.
The cement rock proper is found on the Milwaukee river just above the city.
At the close of
the Hamilton period the oceanic waters retired, and, if they ever subsequently
encroached upon
our territory, they have left us no permanent record of their intrusion.
    The history of the formation of the substructure of the state was, it
will be observed, in an
unusual degree, simple and progressive. Starting with a firm core of most
ancient crystalline
rocks, leaf upon leaf of stony strata were piled around it, adding belt after
belt to the margin of
the growing island until it extended itself far beyond the limits of our
state, and coalesced with
the forming continent. --An ideal map of the state would show the Archoean
nucleus surrounded
by concentric bands of the later formations in the order of their deposition.
But during all the

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