Salt Lake evening Democrat. [volume] (Salt Lake City, Utah) 1885-1887, 1885-06-25
THE GEOLOGY OF THE WEST.
-ePOrt on the Great Plateau and
Mountain Region.

mountain Region.
captain Clarence +. Dutton. of the
ordnance Department of the army. Who
mas been engaged for ten wears in fine
study of the geology OF the great plateau
region OF the West, left Washington re-
Gently for California, under instructions
from Major Powell, Director of the Geo
logical Survey, to make a study of tba
geological phenomena presented bv the
cascade Mountains, the greatest volcanic
range upon the globe. Before his denar-
lure captain Dutton finished the manu-
SCRIPT OF ms contribution to the next an
nual publication OF the Geological SURVEY.
Inc paper is entitled Mount TAYLOR and
the Aunl Plateau" but although it treats
ID detail OF only two features of the plateau
region, the conclusions which these are
made to illustrate embody in part the re-
suit OF years of study extending over q
very wide area. OF the history of the
plateau region, prior to the carboniferous
time, he says: Little is known to geolo-
glsts. In the latter part of this period
the western part of the United States was
marine area. If any land existed it
was OF small extent. The strata deposited
animals among their fossils, while marine
mollusca are abundant. The waters
were neither very deep nor very
shallow In the Immediately sue
ceedlng geological periods, during
the deposition of the permian and
Jura trlas strata, a curious alteration of
land and sea is found to Nave taken
place, in the level surface of the region,
oscillating from a little above to little
below sea level. During its seasons of
elevation it supported exuberant forests,
through which roamed highly varied
reptilian fauna. The region appears to
have subsidized about as fast as the sedi-
ments were accumulated, thus preserving
the surface at nearly constant level,
and it is surmised that the oscillations
may have been due to variations in the
absolute position of the sea level. What
ever may be the explanation, it is q most
extraordinary fact that between 5000
and + 1000 feet of strata were accumulated
upon an area of over 10000 square miles,
and yet the surface of deposition was
maintained throughout at approximately
the same level. During the cretacious
time the alterations from blooming for
ests to shallow seas continued, but the
fossil remains OF this time are of greater
variety, and are found in greater album
dance. Early in this period the mol
tuscan fossils are of the marine type, but
in its upper strata they were OF the
brackish water type" Whence, the
author asks, came the materials which
constitute the mesOZOic strata of the West,
covering nearly 100000 square miles,
to the average depth of more than > 800
square feet? The great basin which has
been enormously raVaged over an era OF
100000 square miles by evasive forces,
furnished portion of the material, and
possibly small land area, insular in char
acter, existed further south. But it is
not credible that these sources furnished
even one-half the materials of the mesO-
Zoic strata. The fact is general that
these strata grow thinner from west to
east, indicating q Western origin, and
the author concludes that they came
from some great continental area, with
coast line many hundred miles long,
with numerous rivers discharging sand
and silt all along its course. Passing on
its tertiary time, the fossils OF the early
eocene strata, are found to be still of the
brackish type, but these are replaced by
the fresh water forms little higher up.
Thus it is inferred that the complete $50
lation of the plateau province was accom-
plished at the beginning of tertiary time,
and its area became, in great part at
least, a vast inland lake with an outlet.
In the eocene age the great mountain
platforms of the Wasatch, WintaS and
Rockies were upheaved and underwent
rapid foundations. The resulting sedi-
ments were carried down into the lake,
where they were deposited, sometimes to
the depth of 5000 feet. With the pro-
gress of eocene time the lake of the
plateau region gradually vanished, the
southern part being the first to dry up,
and with its disappearance ended the
long period of deposition. The accumu-
lated strata reached the thickness OF
Is 900 feet in the western part, and not
less than 10, 800 in the east. At no time
could the surface of deposition have been
very far from sea level. The progress OF
tertiary time witnessed the slow elevation
of the entire mountain and plateau region
of the west, and along with the denuda-
ton of the country the author traces the
geological history of the region down to
its present condition, finding evidences OF
alternating periods of moisture and dry
ness, of great and sudden uplifts OF great
areas. and of the slow denudation OF i'm
mense tracts, and the cutting of canyons
bv the waters. In the study OF
the Zuni mountains he finds rea-
son for the conclusion that the
mountains of the west have not been pro-
duced bv horizontal compression, but by
the action of some unknown forces be-
meath which have lifted them up. upon
the extensive plateau OF which Mount
Tavlor is the centre, he finds ample con-
firmation of the theory that the volcanic
can which once covered so large portion
of the region and which still tops many
extensive mesas, had its origin, not IN
discharges from immense volcanic noun
tains like Mount Taylor itself, but through
innumerable vents through the sediment
arv strata. These evidences consist
LARGELY in the numerous huge ''necks" OF
nnTe lava. from the vicinity of which the
sedimentary deposits have been eroded-
These necks are the contents OF once eN-
isting tunnels, through which the molten IN
lava was forced to spread itself IN IT Ihlll
cap over the level country above; ihey
exnlain the existence of the lava BEDS az az
tho present time so far distant from the
wy 70 1,oIoonic mountain as to preclude