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Wallings Atlas of Wis

GEOLOGY

BY I. A. LAPHAM, LL.D., STATE GEOLOGIST.

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The first considerable effort to develope
the geological features of the territory
now constituting the State of Wisconsin, was
made in 1839, by Dr. D. D. Owen, Dr. John
Locke, and others, in what is known as the
lead region, chiefly in the counties of Grant,
Iowa, and La Fayette, in the south-western
part of of the State.

This work was done in pursuance of a resolution
of Congress, calling for information
relative to the mineral lands of the United
States, and the results were reported in an
Executive document ^1 with maps, sections
and drawings of fossils. The next was also
made by Dr. Owen, or under his direction, on
behalf of the general government, being a
Reconnoissance of the Chippewa Land District
which then included a large portion of
the State. The results were reported in
1848 ^2 with a large map; and again more
fully in 1852 in a large volume on the Geology
of Wisconsin, Iowa and Minnesota.

In Foster and Whitney's Reports upon the
Copper and Iron Regions of Lake Superior,
(1850 & 1851) are some chapters relating to
eastern and north-eastern Wisconsin.

The State has made several efforts towards
a geological survey of its territory, and a
number of "Annual reports" in pamphlet
form have been published. The report of
Hall and Whitney (1862) forms a volume of
455 pages, with maps, sections, and wood
cuts of the characteristic fossils, and is the
only considerable publication heretofore made
by the State. Professors Edward Daniels,
Ezra S. Carr, James Hall, J. D. Whitney,
James G. Percival and John Murrish, have
been employed in this work at various times.

A more complete geological survey of the
State is now in progress, under the authority
of a law approved in March, 1873; but no
report of the results has yet been published.

It is proposed to give, briefly, a general
idea of the principal facts already known by
describing each rock-formation, in accordance
with its relative age, beginning with

I. THE LAURENTIAN.

The oldest and lowest of these formations
found in Wisconsin are granytic rocks,*
which may be regarded as the foundation, or
floor, upon which all the others have been
laid.

There can be no doubt of the great age of

^1 House Ex. Doc. No. 339, 26th Cong., 1st Session 1840.
^2 Senate Ex. Doc., No. 57, 30th Cong., 1st Session 1848.
* This orthography is adopted by Prof. J. D. Dana to
distinguish between rocks and minerals.

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this granytic series of rocks, as was first indicated
by Foster and Whitney, being so far
as was known, older than any organic life
and hence called Azoic: but as they are
supposed to contains traces of organic remains
elsewhere the name Archaean has been
adopted by recent writers. They usually
exist in the form of rounded or dome-shaped
knolls of considerable extent and of but little
elevation. Essentially, granyte consists of
an aggregation of crystalline grains of quartz,
feldspar, and mica; but the name is usually
applied to rocks in which hornblende takes
the place of mica (syenyte), and to other
crystalline aggregations. When slaty in
sturcture it is Gneiss, or Mica-Slate. All
these forms occur in Wisconsin. Some varieties
especially from the Oconto and Wolf
rivers, have a great resemblance to the Scotch
Granyte of which so much is now imported
for ornamental purposes; but no attempt has
yet been made to quarry any of our granytes,
owing to their remoteness from the
means of transportation, being mostly in parts
of the State but little settled and improved.

Other varieties, caused by the varying constituent
minerals, and their relative proportions,
are found, and might be rendered useful
in masonry; including fine grained and
coarse, red, white, gray, mottled, light-colored,
porphyritic, graphic, &c.

Granyte and Granytic rocks are found at
Black River Falls, on the Wisconsin and
Chippewa rivers, and at numerous other
localities within the district represented on
the accompanying map as "Granytic and
Huronian."

It will be seen that they underlie portions
of the counties of Burnett, Polk, Barron,
Ashland, Chippewa, Clark, Wood, Marathon,
Lincoln, Portage, Waupacca, Shawano, and
Oconto. They are so uniformly covered with
"drift" that it is difficult to ascertain their
presence or to trace their boundaries.

II. HURONIAN ROCKS.

Resting upon these granytic prominences,
and sloping away from their sides in all directions,
are often found strata of chloritic,
talcose, or argillaceous slates and quartzytes,
supposed to have the same age as the rocks
which in Canada are called Huronian. These
rocks are of great practical interest on account
of the masses of iron ore associated
with them; most abundantly at the Penokie
Iron Range, in Ashland County, and at
Black River Falls, (Jackson County.) The
famous iron deposits of the Marquette and
Menomonee regions in Michigan are in the

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same series of rock. It is supposed that the
iron range near the Menomonee extends
across that river into Wisconsin and measures
are in progress for ascertaining the truth
of this supposition.

The Penokie iron-bearing rocks have been
traced for a distance of sixty miles; always
accompanied by magnetic and specular iron
ores varying from a few feet to one hundred
in thickness. The ore is mixed with the
rock in proportions varying from one or two
to eighty per cent. They have been carefully
"sampled" and analyzed, so as to show
their practical value; and it is believed that
as the country becomes better known, richer
and more easily worked deposits may be
found. The completion of the Wisconsin
Central rail-road will bring this now almost
inaccessible region into notice.

Roofing slates are quarried in these rocks
in Michigan and suitable localities may be
found in Wisconsin.

Huronian rocks are found in Ashland,
Bayfield, Oconto and Jackson Counties; also,
in the form of quartzytes, in Sauk, Columbia
and Marquette. No doubt older localities
will be found when these other rocks have
been more thoroughly studied. It is believed
that they rest non-conformably upon the
granytic rocks, as represented on the accom-
panying section; but this fact has not yet
been confirmed by observation within this
state.

The quartzytes in Sauk County show ripple
marks upon surfaces now standing almost
vertically; thus showing that they were once
horizontal sand-beaches, that have been hardened
and tilted up to their present position.
They were also at a very early period broken
up into boulders and pebbles that were again
cemented into layers of breccia and conglomerate.
Thus boulders were formed long
before the glacial or ice-period. By the disintegration
of these conglomerates, boulders
are reproduced that originated in Archaean
times.

Kaolin or Porcelain clay is found in several
localities, resulting from the disintegration
of the granyte and the decomposition of
feldspar. Some efforts have been made to
use this clay in making fire brick for lining
furnaces which seem to have been successful.

Pipe clay, similar to that so celebrated
among the red men, from the Coteau de
Prairie, Minnesota, has been found in Barron
County upon lands belonging to the Cornell
University of New York. It was first discovered
and described by Mr. A. Randall in