Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1946-12-21

Field and office work on the re-
vision was started in September,
1913, by c. E. Erdmann and was
continued during the fall and win
ter of 1916 and 1916 by William
Beer and ]. w Nordquist.
The revision embraces all ele-
ments of the older map, which COW
cred Twps. BON to BIN, inclusive,
and Rigs. 3W to SW, inclusive, an
area of ,728 square miles.
The practice of showing structure
contours on the top of the Colorado
shale at 100-foot intervals has been
continued, but the accuracy of the
contours has been improved and an
Interpretation of faulting has been
added Other significant changes
and additions include stratigraphy
of the lower Kootenai productive
sands, areal geology, culture (roads,
airport, etc., field development
Approximately LOO new well loca-
tons, oil and gas pipelines, refinery
ownership and figures of oil and
gas production for the Cut Bank
field. The map now shows by stan
dard symbol the productive status
on April /, 1916, of more than / $50
wells drilled for oil and gas. A STRAIT
iEEdDItH( NlOo0 nCLlAOtl ~nAAOo0 tkAI
Chalk Butte nose and the north Cut
Bank and west Kelvin districts is
included. as in the earlier edition
The map may be purchased from
the director, geological survey,
Washington 25, ID. c., at 25 cents
a copy and is also available for over
the-counter sale at the geological
survey offices at 314 Boston build
ing, Denver, Colo; 3O5 Federal
building, Casper, Wyo.. and Com
mercial club, Billings, Mont.
The surface of the region is Oc-
cupied by widespread deposits of
glacial drift and alluvium that are
not shown on the map. All exposed
rocks are of Upper Cretaceous age.
Recognized formations are, in down
ward sequence, the Horsethief sand
stone, Bearpaw shale, Two Medicine
formation, Virgelle sandstone and
Transition Zone Telegraph Creek
equivalent) that constitute the Mon
tana group, and the upper one-third
of the Colorado shale Concealed
rocks consist of the remainder of
the Colorado shale, including the
Blackleaf sandy member, the Koo-
tenai formation of Lower Creta-
ceous age, the Ellis group of Jur-
assic age, the Madison limestone of
Lower and Middle Mississippian
age, and the Three Forks shale and
Jefferson dolomite of Devonian age.
Pre-Devonian Paleozoic sediments
are doubtless present but have not
been drilled into in the map area
This general sequence, with signif
icant variations in thickness and
character, Is shown in columnaI
section on the map.
The geologic structure of the re
gion is dominantly homoclinal with
an inclination of about 100 feet pei
mile west from the crest of the
Sweetgrass arch, which is few
miles east of the map. This condi
ton is diversified by a series o.
terraces and anticlinal noses tina
plunge north-northwest, some o
which include areas of small loca
closure. Several small epi-anticlina
faults have been developed by con
touring in Cut Bank oil field. Sub
surface evidence for their existenc'
is suggestive, but it is not conclu
sive, and they are not expressed a
the surface There is some additi
onal structural and iSo-oil gravit1
contour evidence that similar fault
may cut the sands that yield tn
oil and gas. If this is so, operator
might bear in mind that such fault
may serve to divide the field int
units that may have a significan
effect on both production and SEE
ondary recovery programs.
Production in the map area
chiefly from the Cut Bank oil an
gas field, and from various oil pool
in the west Kelvin district. Smalle
producing areas are the nearly e.
hausted Border Red Coulee fiel
and the Darling, High Gravity, Re-
gan and Thorpe pools.
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