Grant County herald. [volume] (Lancaster, Wis.) 1850-1968, 1878-03-07
GEOLOGY OF THE LEAD REGION

TRENTON DUFF AND BLUE) LIMESTONE.
Geographical Boundaries. 1t will
not be necessary to enter upon a de-
tailed description of the ground COW
cred by this formation. 1t is suffi-
Gent to say that it is always found be.
tween the lowest bed of the Galena
limestone and the top of the St. Peters
sandstone, and having an average
thickness of about fifty feet.
Theological characteristics. The
Blue is remarkable as being the purest
limestone in the Lead region, and the
nearest approach to the Trenton lime
stone of the eastern states, both in it's
Theological and archaeological char
acteristics. A very noticeable feat
ure is its marked division into two
parts; one very heavy-bedded, in lay
ers of two or three feet thick, known
as the glass rock, whicl constitutes
the lower half; and the other, thin
bedded, in layers of two or three
inches, graduating sometimes without
much change into the thin.bedded
Galena limestone above. 1t is at this
point that the stratum of carbonaceus
shale occurs, which is the line of de-
narration between the Blue and Ga
lena llmestones, and as such, is an un-
failing guide. 1t varies very much in
its thickness, being from a quarter of
an inch to foot or more, but wher-
ever a good exposure of the two for
nations is seen, it has uniformly been
found.
The carbonaceous shale attains its
greatest thickness in the vicinity of
Shullsburg, At the Oakland level on
the S. w. ar. of Sec. 5, t. /, r. 2, E.,
it varies from one to two feet X and
at the grounds of the Silverthorn mine
on the N. E. or. of Sec. 81, T. 2, r.
2, E., it has a thickness of seven feet,l
affording in each OF these localities
small but handsome crystals of Galen-
lite, having smooth polished faces,
which is but seldom the case with
crystals of this mineral found at other
localities in the Lead region
\ Prof w. w. Daniels, of Madison. has
made the following analysis of the shale car
bonaceous matter, 1880; carbonic acid, 0.SS !;
water, $50.
Also the following analysis of the Silver
thorn shale:
% Carbonaceous matter, 1881; carbonic
acid, 1856; water, 0.4O.
(2) Carbonaceous matter, 1915 carbonic
acid, 0.60; water, 0.S2. No. of the Silver
thorn shale was quite dark colored. while No.
was "a lipbt sh-a0lorpd cha1a
The specimen from Oakland had been for
several years exposed to the weather.
The following section taken from
the Darlington quarry will give a
good general idea of the formation.
The quarry is situated on the N. E.
or. of Sec. 3, t. 2, r. 3, E.:
GALENA LIMESTONE.
F. In.
/. Soil and Loose rock. ....... .
2. Yellowish, hard, compact dolomite,
similar to the Buff on the surface,
but not blue between the layers,
evenly bedded in layers one foot
timex.
s. Thin layers two to four inches thick -.
4. Carbonaceous shale... ....... =. 2
Blue LIMESTONE.
5. Thin-b edded, very fossferous lime
stone, in layers from two to five
inches thick. .......... 6
g. Heavy bedded, dark blue limestone,
very hard and compact, unfossilif-
erous except in the shay partings
between the beds2 ............. IL -.
The following is an analysis, by Mr.. E. T..
Sweet, of the Glass rock from Mineral Point,
corresponding to No. of the above section ]:
Silica. -. 6.l60