Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1941-02-22
from the two groups OF seepages.
Problem OF Source Beds

EEUDAHxM VI %NMANG AAC4S
PRE-CAAdBRLAN-Aceording TO
Daily, the Belt series, in the vicinity
OF the Cameron Brook and Sage
Creek seepages, consists II thin
to-thick-bedded, light gray. gener-
ally sandy, siliceous magnetism
limestone Of the Allyn formation,
and massive, dark gray fields
pathized' dolOmite OF the WatertOn
formation. Examination of these
beds at their outcrops and OF cores
from diamond-drill holes on Cam
eron Brook shows that the oil oc-
ours In crevices or fractures. This
does not preclude the possibility
that these pre-Cambrian sedimen-
tary rocks may. at some time. have
yielded hydrocarbons. However,
the possibility that the present see
pages are fed from source beds
within the Belt series Is not worthy
OF serious consideration.
"CAMBRIAN-The Cambrian sec
ton consists OF a great thickness
OF siliceous dolomites. magnetism
limestones. varlOusly colored argyll
lites and metargillites as we'll as
quantities, some of which, in their
prem etamorphosed stage, might
have contained oil source materials.
In their present state they can not
be regarded as the source beds for
the seepages under consideration.
UPPER PALEoZoIC SECTION
At and near the 49th parallel,
there are no upper Paleozoic rocks
exposed in the Lewis & Clark
ranges. but their presence farther
west in the Macdonald Range,
the ~Flathead valley, as we'll as
farther northward, merits their con-
sideration as a possible source rock
for the seepages which are found
in the Clarke Range. Devonian,
Silurian and CarboniferOus lime
stones, dolomite and shales which.
in the light of recent researches
on petroleum source rocks, might
readily be regarded as source beds,
are widespread In the Rocky Noun
tains. Much OF the Devonian and
Carboniferous is limestone and
dolomite. highly cavernous, porous
and fossiliferous.
Origin OF Naptha
"At Turner Valley the produc
ton of wet" naptha-bearing) gas
in large volumes is confined to
limestones and dOlomite Of Car
boniferous age. Although the de-
termination of the precise strait
graphic position of the source beds
CT the Turner Valley production Is
questionable, one may safely state
that upper or middle Paleozoic and
possibly the Jurassic are the main
sources.
IF the Turner Valley production
can be used as a criterion for the
seepages in the Clarke Range, 1t
seems permissible to ascribe a pos
sible source for the seepages to
middle or upper Paleozoic beds
presumably limestones or dolOmites
Of Devonian or Carboniferous age.
Reviewing the formations above
the Carbonifereus madison lime)
Mr.. Link said that oil and gas pro-
duction in the Sweetgrass Arch oil
fields are highly suggestive OF
source beds within the Jurassic. He
dismissed the likelihood that the
Cretaceous section is source mater
ial, adding Small shOwings of oil
are, however, encountered in the
lowermost Colorado of Turner
Valley. This oil is the darkest and
heaviest encountered in the field"
The Tertiary section can not be
regarded as an adequate source of
the Sage Creek seepages. conclud-
ing:
CONCLUSIONS REGARDING
SOURCE BEDS. -SummarizinR the
aspect of source beds, it seems con-
to state that neither the
Tertiary nor most OF the Cretaceous
section could be regarded as the
primary source rock for the Cam
eron Brook and Sage Greek see
pages. The ultimate source beds
for the surface manifestations are
in all probability the upper Paleo-
zoic (Devonian. Carboniferous, or
both) and possibly the Fernie
(Jurassic) beds. Small amounts
from the Colorado shale may, how
ever, have been an important factor
with respect to the Cameron Brook
seepages."
After discussion Of reservoir rock
and structure he wrote:
Similar To Naptha
THE color, gravity. and charac-
ter OF the oil from the Sage Creek
seepages suggest an origin similar
to that of the Turner Valley naptha.
There is a possibility that the hy-
drocarbons within the underlying
porous Paleozoic dolomites might be
in vaporous, or even liquid, state