Evening star., 1934-11-21
ROCKY MOUNTAINS
HELD TWO CHAINS
Scientist Says New Data
Explains Difference of
Southern Range.
BY THOMAS r. HENRY.

The Rocky Mountains probably con-
sist of two distinct parts which just
happen to be contiguous.
Such is the deduction of DR.. Charles
E. Resser, Smithsonian Institution
paleontologist, based upon his study
of conditions in the lower and middle
Cambrian geological eras, approx
mately 500, 600, 900 years ago, and the
imprints left in the rocks by the
earliest living creatures of which
science has any knowledge. Events IN
that distant past, according to DR..
Resser's reconstruction, explain the
present difference in the scenery OF the
Northern and Southern Rockies and
the necessity for different engineering
methods of road building IN the two
areas. The two systems come together
in Yellowstone National Park.
1t was during the Cambrian, DR..
Resser says. that the fundamental
conditions were established. The actual
mountains of today are much younger,
having constituted the sea bottom
several times since then.
Sea Over Continent.
During the Cambrian, as throughout
most of geologic history, long. mar
row, shallow arm of the Arctic Ocean
extended southwark into the low-lying,
fat North American Continent. The
waters swarmed with curious crab-like
creatures known as trilobites and
shelled animals of the lamp shell
family. When they died their hard
skeletal parts sank into the soft ooze
of the sea bottom where they made
imprints which remained when the
mud became rock.
The course of this embayment can
be followed roughly through the i'm
prints of the earliest animals SOUTH
ward through Canada to Montana.
Cambrian deposits again are picked
up west of the Rockies and continue
southwark to the Great Basin. The
implication has been that there were
two Cambrian embayments. the sec
ond entering the Pacific in the neigh
borhood of what is now Los Angeles
and extending northward through the
Great Basin
But recent Cambrian finds, speci-
mems from which have been sent DR..
ResSer to identify, indicate that there
was only a single embayment. It
followed the general course Of the
Northern Rockies, but turned west
ward in Montana. continued along
the so-called Rocky Mountain trench
between the Rockies and the Selkirks,
passed through the Great Basin and
extended south as far as Southern
California. 1t passed west of the
present Southern Rockies.
Ancestral Mountains.
Many geological periods later the
rocks deposited in this embayment
were folded up, forming the heights
ancestral to the Northern Rockies of
today and the mountains of the Great
Basin.
During the lower and middle Cam
brian, sea waters were not permitted
to enter the region of the Southern
Rockies, but in the upper Cambrian
there was widespread flooding of the
continent. The shallow seas, with
their abundant fauna, spread into
basins between islands, so that much
OF North America must have ap-
peared like great archipelago
These islands were the highest spots
OF the ancient land. They now con-
stltute the cores of the ranges of
the Southern Rockies, such as the
Big Horn Range, the Black Hills and
others.
Around these cores the upper Cam
brian seas deposited sediments at a
very slow rate. The same phenomenon
is in progress in the West today, but
on much greater scale. The upper
Gambrian islands were low-lyine lands
with slow-flowing rivers that could
carry only the finer materials.
Difference Pointed Out.
1t is due to this different history.
says DR.. Resser. that the scenery of
the Northern and Southern Rockies
is so different. North of Yellowstone
the thick masses of sediment laid
down from the Cambrian to the coal
period in the embayment were folded
and faulted to make castle-like noun
tains such as those of Glacier Ma
tional Park and Canada. Southwark
the granite cores were uplifted so
that there rather thin sheets of sedi-
ment resulted in the so-called hog
backs'-such as are typical of the
Garden of the Gods. The tops of
these ranges today constitute a roll
ing, fiat country roughly similar. ex-
cept for the presence of land vegeta-
ton, to the appearance in the upper
Cambrian.
Hitherto, the Rockies have generally
been looked upon as a continuous
mountain system all of whose parts
owe their existence to the same basic
phenomenon in past ages. The new
Cambrian data shows that the two
parts are at the best distant cousins
with no direct ceneric reIo otiopeb;r