Manchester Democrat. [volume] (Manchester, Iowa) 1875-1930, 1921-02-16


! tricts of Iowa are known as the
"older" and younger" drift areas
There is marked contrast between
the driftless area and the areas oil
drift-covered territory. River eros.
ion is responsible for the land forms
with the exception of sand dunes
and ridges which have been formed by
the action of the wind. Many streams
flow Between the rugged and pictur.
esque hills and bluffs into the Miss.
issippi. They are actually and rap.
idly shaping their gradients which
are now high. In distance of thirty
miles there is a decline of 600 feet
from the summit of the ydolomitic
cliffs to the low flood plain. Walls
from $50 feet to $50 are common in
the Southern portion of the area. Al
the north the valleys are still deeper
owing to the rise of the strata.
The rock formations belong to the
Paleozic age and include shales, dol
Omites, sandstones and hard lime
stones. The Galena cliffs rise 23O
feet above the Mississippi river in
| Dubuque county. From this level
there is rolling open plain rising
from $50 feet to ITS feet to the base
Of the Niagara. This is known to the
| biologists as the Horizon of the Ma
| quoketa shales.' The Niagara cliffs
rise above this plain from 100 feet to
200 feet Isolated patches in the form
OF mounds stand out upon this plain
as sentinels in the scenic beauty of the
region.
Although many Of the valleys are
thread-like and narrow, they have the
marks of age. Extensive slopes and
rounded cliffs near the mouths of these
streams evidence long and undisputed
action. Long slopes covered with
grass hide the cliffs, and talus have
accumulated where the streams have
not impigned against their banks in
times of flood.
The Oneonta or Upper Iowa has cut
valley $50 feet below. the immediate
ly adjacent territory and more than
600 feet below the highest points in
the region. In Allamakee county the
Onenta and Galena-Trenton imestones
form the lower and upper cliffs, the
easily eroded st. Peter sandstone
forms the base of the structural plain
From Dubuque north there is a con-
tlnuous succession of cliffs fronting
the river. From these cliffs extend
long grassy slopes, which eventually |
reveal insignificant streams at their
feet. These streams in some instan-
ces have cut to the level of the main
valley. Treneplano mountain is one
of the best examples Of this feature.
During the Wisconsin period it is
believed the Mississippi river flooded
much and as a result it is Dor
dered by we'll developed gravel ter
races. The tributaries of the Miss
issippi have corresponding terraces.
The small neighboring valleys show
what the character of the Mississippi
river must have been before it was
turned into its present course. The
channel must have been widened. No
doubt the Mississippi river was
small stream before the ice invasions,
out the dendritic arrangement of the
tributaries show that the present val
ey has long been the valley of the
channel of the main stream. It is not
definitely known when these valleys
we're cut.
Strange coincidence of nature that
his comparatively small area should
lave been left by the ice invasions as
hey flowed down from the north.
some think that the plain at the top
II the Galena correlates with the ter
larry cycle of erosion, and that which
ouches the tops of the mounds cor
'elates with the Cretaceous. lam
'rlan sandstones are found in the ;
)neonta valley, and crop out in ALA
nakee and Clayton counties. They
re found as far west as Winneshiek
county. The depth of the formation
s estimated at 1900 feet. Its strata
of the Basal sandstone which
covered by the Lawrence shales and
on top of which is the
Jordan sandstones.
The OrdOvician, or Lower Silurian
les above the Cambrian and near the
Niagara escarpment. 1t extends from
northeast Howard county to Clinton.
Inc thickness is about equal to that
u the Cambrian. 1t consists of four
MEMBERS with minor subdivisions
Inc lower is the Oneonta dolomite of
wo divisions separated by the new
richmond sandstone. This is some
lines called the Lower Magnetism.
It Is this that gives the picturesoue-
hess OF Allamakee county. st. Peter
which is exceedingly pure.
1es above the Oneonta Dolonite. It'll
IS covered with the Galena-Trentonl
series. The lower series is undolo-
notlzed and is known as the Trenton
mat which has been dolomotized has
been named the Galena The cliffs
around Dubuque are formed of these
rocks and are the source of the lead
and zinc ores of Iowa.
Maquoketa, or Hudson river shales
stretch above these cliffs to the base
0f the Niagara escarpment. The Mia
CARA, or Silurian, although Invisible
INTO several minor formations is gen.
orally considered as making up dolo-
Noticed limestones stretching over the
entire area of northeastern Iowa.
The Sioux quartzite, Devonian.
Lower and Upper Carboniferous and
The Cretaceous lie over the other Dor
tons of the state.
Northeastern Iowa stands out as a
rugged and majestic piece of Gods