St. Charles City Republican intelligencer. [volume] (St. Charles City [Charles City], Iowa) 1857-1861, 1859-05-12

mlnatlon OF one or the highest ridges
in this region, which runs up from th,
southeast to within short distanc,
of Lime creek.
The upper bed Of the section con
tains an abundance of fossils. which
are washed out by the rain from tht
decomposing rock. Among these were
observed, Atypa rugosa or spinosa, A
raicuiaris, Orthis one or two new spe
cies, Spirifer n. sp., Strophomena, and &
few Hamilton corals.
On Shellrock creek, at Rockford
the exposures of the rocks are very
limited There is light greyish buff:
colored stratum, which is somewhat
argi'laceous dolomite, but rather soft
and worthless for building purposes
succeeded by bed of slightly darker
color, but of essentially the same
character. These beds are probably
lower in the geological series than
those indicated in the preceding sec
| ton.
At ShelIrock falls, in Cerro Gordo
county, about thirteen miles above
Rockford, the absence of fossils in the
beds exposed renders it difficult to as
sign them any certain place, although
from their position, they may be sup
posed to belong to the upper part of
the Hamilton or the Chcmung group.
They consist of thin bedded hard and
rather crystalline magnetism lime
stones, varying in color from light
grey to almost black. The exposure
of the rocks at this locality is good,
but the most careful search failed to
reveal the presence of any fossils.
The Theological character of the rocks
at Shellrock creek and falls is peculiar,
and nothing exactly like it has been
observed in other parts of the State.
They are all highly magnetism but
not pure dolomites, as they contain
rather more lime than belongs to the
composition of the double carbonate
of lime and magnesia. The speci-
mems from Shellrock creek have a
considerable resemblance to those from
Cedar falls, which are referred to the
Chcmung by Mr.. Worthen, with some
doubt as to their real position, since
they are quite unfossiiiferous. The
beas at Shellrock falls are very mag
nesian lmestones, or dolomites with a
little excess Of lime, and are remarka
bly, free from siicious are argillaceous
substances. One specimen analysed
from this locality, contained less than
two per cent. of impurities mixed with
the carbonate Of lime and magnesia
These beds are too irregular in thci,
texture for good building.stone, some
of them being hard and brittle, and
others soft and perishable. They are
valuable, however, for lime, and some
Of them will probably furnish good hy-
draulic cement.
In Mitchell county, one and halt
miles above Newburg, on the Cedar
there is a tolerablc exposure of the
rocks where the following section was
observed:
Crystalline limestone, sandy at the
bottom, but growing more calcarcou.
towards the top-2 feet.
Dark-grey thin-bedded limestone
8 inches.
Dark-grey hard and brittle lime
stones in heavy layers, varying from
inches to feet in thickness.-l3 it
in.
Rock not exposed, down to level Of
dam at Newburg-2 it. in.
Another section was measured a
Newburg, the base of which is on tn,
same level with the preceding one
but as there is little agreement il
their details, it appears that the dip o
the strata has probably carried tho
beds of the upper one below those o
the lower.
The section at Newburg is as fol
lows:
Beds of detritus with Spiriter, O
irregular thickness.
l3. Hard brittle light greyish-yel
low magnetism limestone-4 feet.
l2. Unexposed-4 feet.
IL. Hard light-grey somewhat crys
talline beds, with concretionary bands
of darker color-S feet.
TO- Soft sandy beds with clay:
feet inches.
9. Hard light-grey silicious lime
stone-l it. 3 in.
8. Hard limestone like No. 9, de
composing into sandy rock--l0 in.
I, 5, 5, 4, 3, 2, l. Beds of hard buff
grey limestone varying from to IA
inches in thickness, and in various
stages of dccomposition-4 IT. 4 in.
Unexposed, to level of river at New
burg-6 feet.
In this section, No. ii and No. l:
contain Spiriftr closely resembling S
mucronatus no other fossils were nc
ticed
Prof. Hungerford remarks in regar,
to the Theological resemblacces of tn
rocks of these two sections, that ther
is very great similarity betwee
some of the beds of the Newburg sec
ton and those noticed on the border
of Winneshiek and Chickasaw cour
ties, near the one from Fort Atkinso
to Jacksonville, in descending tn
high ridge towards the Little Turkey
ln this vicinity, near lime-kiln, loos
masses Of limestone were observed
marked by concretionary lines, an
having that peculiar sottness and fine
ness Of grain which was noticed abov
as belonging to bed No. ii Of tn
Newburg section. The same rock
seen in No. of the section, eieve
, aud a half miles below Jacksonvill
on Crane creek.
!. ave say to our farmers-plant an
7 sow freely. persistently for graf