Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1932-11-26

For The u s. G. S. and Eugene Stebinger

been THREE periods Of uplifting in
Northern Montana and Southern AL
berta. That Is the reason that
many OF the hills. such as the
sweetgrass Hills. came up COLD.
They are hills OF volcanic origin.
oct there Is no evidence OF heat
in the shaies around them. Had
they come up a. hot lava they
would have burned the shale into
slate. These hills were of vol
oanic origin and started upward
In pre-Cambrian times. The pres
sure was not great enough at that
time TO force them through the
surface. The pressure from below
created buldges in the earth's sur
face. however Then came a Sc
cond period Of distnrbance and the
igneons masses were again thrust
upward by tremendous forces be-
meath. This time they forced their
way through lines OF ocean beds and
shales OF continental deposits which
had perhaps been formed between
the time Of the first and second up
lifting.
Then came q third tremendous
pressure from below and these
igneous plugs, now almost entirely
cooled OFF. were thrust through
the surface OF the prairie. The only
evidence Of heat Is the metamor-
Dhism adjacent to the granite mas
ses-heat created By the friction.
This is our hazy recollection Of
the story Of the sweetgrass HllIs
as written By Weed OF the q. s.
@. s., Dawson OF the Canadian
Geological Survey and others
Under the clrcumstances. It stands
% reason that the entire sweetgrass
Arch may have been an island with
an area OF more than 5000 square
miles at the time the Ellis was
laid down and thereafter during
the early Cretaeeous.
In our Bulletin No. 1s4 on the
Sweetgrass Hills we reproduce q
map which shows the shape and
location Of the inundation Of this
region in the early cretaceous times.
It would appear that the coast or
beach was along the west edge
OF what is now known as the
sweetgrass Arch. Because the same
forces which created the mountains
created the Arch. 1t is not at ali
impossible that the surface exposures
may guide us In concluding the To-
cation Of the ancient coast.
Again we are positive that the
Kootenai formation thickens to the
west. At Cat Creek II Is about
400 to 500 feet thick. At the
East face OF the Rocky mountains
1t is NINE HUNDRED feet thick.
and in British Columbia on the
WEST side Of the mountains, the
Kootenai (Blairmore) Is TWO
feet thick.
1t is interesting to read stebin-.
gers description OF the formations
which be said in 1918 would pro-
duce oil: (The capitals are ours.)
II is believed that fhe sand
stones in az least the upPer part
Of the Koofenai formations closely
associated with the overEying pet
roIiSer0us rocks in the lower part
Of the Colorado, offer . possibility
Of being productive Of OH or gas.
The Ko0tenai in the area here des-
cribed has q total thickness Of about
boo feet and Is composed essentially
of shale and clay shaleg that are
mostly red and purple, alternating
WITH SIX TO EIGHT BEDS OF
GREY TO GREENIsH GRAY MED
IU1E 10 COARSE GRAINED SAND
STONE BETWEEN 80 and 80
FEET IN THICKNESS AND
RATHER EVENLY DISTRIBUTED
THROUGHOUT THE FORMATION.
The Kootenai formation % this
1rea IS overiain BY . thickness Of
about 800 feet OF dark bluish-gray
% black shale, which contains .
number o. sandstone beds in it's
over third and makes up . dis
.inctive stzatagraphic mnit known IS
he Colorndo shaie. This aoCumnla-
ION q material was deposited I'm
Upper Cretaeeous time on the bot
ON Of q great sea which occupAed
much o. the Great Plains and Rocky
Mountain region and IN q generni