Bonners Ferry herald. [volume] (Bonners Ferry, Idaho) 1904-current, 1922-07-13

issue of the Herald and written by
Prof Virgil r. d. Kirkham, assistant
geologist. School of Mines, Univer-
sity of Idaho, for the Herald
Over 500 million years ago, the
region that is now the panhandle of
Idaho was underlying a deep sea.
i The continent of North America has
had, through the past ages, certain
areas which were prone to become
submerged and covered by deposition
sidence. These are called negative
areas as opposed to certain positive
areas which rarely, if ever, became
submergedeand covered by deposition
The positive areas, suffering erosion
furnished material which was de-
posted in the vast seas of the
negative areas to build up tremen
Gus thicknesses of sediments.
! Northern Idaho was one of these
negative areas and supported a vast
sea so persistent that $4,000 feet of
sediment was laid down in it's waters
before it receded. This was in the
days when animals had no shells. 1t
may even have been previous to life;
at any rate these great areas of beds
contain no fossils, and their relations
TO later rock convince us they be-
longed to the earliest period of sed-
imentation. They have suffered and
withstood various movements and
agencies that have attacked the earths
crust in the intervening 500 million
years but have become somewhat
changed as a consequence. They
were originally sedimentary beds of
shale, limestone, sandstone, and in
termediate variations of them: ripple
marks, sun cracks and thin bedding
show their shallow water manner of
dispositions, but we now class them as
metamorphic rocks called schists
states, argillites, quartzites, marbles
and the like. Heat, pressure dis
tortion and hot water have conspired
to re-crystalize many of the minerals
and they present vastly different
texture, color hardness and general
appearance than their original sedi-
ments during the first period of ex-
stence.
The geologist calls these rocks the
Algonkian Group, and the area lying
in North idaho, Montana and Canada
probably represents the largest area
of their kind in North America. Thel
greater part of these older metamor- |
phic sedimentaries are known as the |
Belt Series.
Many areas of igneous rocks are
exposed in this region They are
mainly GRANTEES and similar rocks that
cooled from molten magmas which in Il
truded these older sediments at |
date long after they were deposited. |
Many of these igneous exposures re-
suit from the stripping away of the
overlying Belt Series by the age-long
erosion of running water and the ice /
sheets.
In the days of the intrusions of
these great bodies of molten magma |
into this everything crust sufficient
disturbances occurred to change the |
originally horizontal or nearly hor-
zontal position of this great mass of |
old sedimentary beds.
Resulting from the great tensions
and compressions applied to these
fairly resistant strata, great folds /
were developed. Where the beds /
were particularly resistant to the for
ces, breaks would occur permitting one
side of an area to drop below the op-
posite side Often when this force
were continued one great layer would
slide over the other part of itself
which had been broken off. These
breaks which are common throughout
the Belt Series are called faults.
Many Of the faults in this country
are remarkable for their vast size
and persistence, indicating the tre-
mendous stresses that have been so
important a factor in developing the
geologic and photographic appear
ances of the region
Four great photographic provin-
ces are contained in or border upon
the area of this description They
have been produced by the faulting
and folding of the older Belt rocks by
great intrusisions of magma and
crystal disturbances of the same area
They are represented by two noun
tain ranges and two great valleys,
known respectively as the Cabinet
Range. Purcell Range. Purcell Trenc,
and Kootenai Valley.
Cabinet Range
This range begins at Bonners Ferry
and extends southeastward through
Montana to the Flathead river and
Jocko Creek. 1t is bordered by the
Purcell Trench and part of Clarks
Fork Valley and is cut into two por-
tions by the deep trench of Bull
River and Bull Lake. The western
region southeast of Bonners Ferry is
a great plateau that is dissected, or
cut up. by stream erosion and gla-
citation.
Hardness of the strata and recur-
rent alpine glaciation has effected
serrated details which are repre-
sented by highly picturesque sculp-
ture. Scotchman Peak represents one
of the most majestic features of this
landscape. Some parts of this scenic
range, lofty and rugged in it's top
ranhv are t-ar-.- i'm r,r.occi..o ....a -.