Great Falls tribune. [volume] (Great Falls, Mont.) 1921-current, 1922-11-26

promising formation for oil production
south Of the Little Rocky mountains.
Ellis formation-210 feet-Greenish
yellow to brown limestone, shalc and
sandstone of marine origin Nearly
equivalent to the Sundance formation
of the Black Hills, S. D.. Reported
to yield oil at Kelvin.
Madison group, Mission Canyon lime
istone-5OO feet-A massive white lime
siliferous as the Iodgepole limestone.
! Yields oil in the Soap Creek field.
Madison group, Lodgepole limestone
500 feet-Thin bedded limestone and
shale. Contains many fossils. Con-
! tains albertite near Landusky.
Devonian. Jefferson 1imestone-35O
feet-Upper $50 feet massive dark
limestone, lower 100 feet thin bedded
limestone. Fetid odor indicates the
presence of disseminated oil. The Ath-
abasca tar sand derives its oil from the
Devonian.
Big Horn limestone-35O feet-Light
colored massive sandy limestone. Fos-
sis principally corals. Fetid odor in
dicates presence Of disseminated oil.
Deadwood formation-SO0 feet-Thin
bedded limestone, shale sandstone and
intraformationaf conglomerate. Con-
glomerate or quartzite at base. Frag-
ments Of trilobites and d small brchio-
pod. May be oil bearing in favorable
localities.
Unconformity.
Schist, mica. %hornblende and field
spar schists. No possibility of oil.
The Quinn Dome
The older formations from the
schist up to and including the Mission
canyon limestone of the Madison group
are exposed principally within the
mountains; the younger ones, from the
Ellis to the recent formations. encircle
the mountains. The rocks of the
Judith river formation are exposed in
many places-in fact, the judith river
is the prevalent formation of the
plains in this vicinity. Sloping away
from the mountains are terraces at
different elevations. which are covered
With gravel derived from mountains.
This gravel, which conceals the under
lying rocks in many places, is prob
ably of Tertiary age and is thought
to be. at least in part, equivalent to
the F1axville gravel. The Little
Rocky mountains are due to intrusions
of porphyry, which raised the sedi-
mentary rocks in great domes.
. HThat the West and Morrison
buttes are laccolithic domes that have
been eroded down to the Madison
group; and that laccoliths underlie the
dome surrounding the southwest cor
ner of sec. is, T. "A n, r. "a E.,
which is here called the Quinn dome;
the dome on which the Phillips ranch
house stands, in sec. IA Of the same
township: and the Grouse-Alder dome.
in secs. 10 and 16. T. "a n. r. % Z.
The Quinn dome is nearly circular
and exposes the Judith river forma-
ton, the upper beds of which lie about
thr~ee-quarters of a mile from the
southwest corne of sec. Is. T. "a n.
r. "a f., and in places form an es-
carpment surrounding the summit of
the dome. The dips away from the
directions and are about IL degrees on /
the outer margin of the Judith river
formation. A well drilled on the crest
of the dome should reach the Eagle
sand at 4 depth of about. 500 feet,
the Mosby sand at about 1900 feet,
the Mowry scale at about 1000 feet.
the Cat Creek G.? SAND at about
$500 feet, and the lower sandstone of
the Kootenai at about 1900 feet.
Other Domes
The Phillips dome. in secs. IS, IA,
23 and "a, Il. q n. r. "a f.. ex-
poses a small area of Judith River
sandstone and is not so nearly cir
cular as the Quinn dome. being flat
tened on the northeast side. The alb
sence of exposures of bedrock on the
northwest side renders that part of the
mapping uncertain. but it is thought
that the dome is fairly complete,
having a good closure on all sides. The
depths of the sands that are most |
likely to yield oil are about the same
as in the Quinn dome.
The Grouse-Alder dome, in secs. Is
and 16. T. 81 n, r. % F., exposes
the Mowry shale in an area of about