Great Falls tribune. [volume] (Great Falls, Mont.) 1921-current, 1922-11-26
FORMATIONS BELOW MADISONIAN
TO BE TESTED in LITTLE BELTS

Nature is looked to for aid in a
proposed test of the lower formations
not previously prospected in drilling
in Montana. This aid will be given
through taking advantage of the years
of erosion.
The proposed test of the lower
formations lying below the Madison
and including the Devonian, Silurian
and Cambrian rocks would be made on
the Little Belt fold lying in Judith
Basin and Wheatland counties, a
structure first passed upon by John
a. Ross and leased through him and
his brother. c.. Nj. Ross. A deal has
been negotiated whereby the struc-
ture will be drilled soon. Oil men will
follow operations with interest. not
only from the point of view of pos
slble production but for the informa-
ton that the opening up of the lower
start in the Madison, making the
Devonian less than 1000 feet below.
Should production be obtained in the
lower formations. it would have a
pronounced effect upon the explora-
ton of virtually every field in the
state. At the present time, only two
wells have been carried into the
Devonian. Probably the most familiar
OF these to oil men of the northern
field is the Troy-Sweetgrass well in
section 21-34-1 W, where the diamond
drli was carried a part way into the
Devonian. Oil was found in ~creyices
IN the shale but no oil sand or pro-
duction n any quantity was obtained.
Sharply Folded AnticIine
OF the Little Belt fold, Roos said:
The Little Belt uplift is commonly
referred to as a mountain range. How
ever, from a geological viewpoint it IS
best described as an elevated plateau
region, owing its prominence to the
erosion of softer formations and its
ruggedness to stream dissection, which
has carved Madison and older rocks
forming numerous gulches and canyons.
The eastern extension of the Little
Belt plateau region narroWs to an anti
clinal ridge seven and one-half miles
in length and thinly forested in con
trast to the bordering plains.
The structure of the ridge is that
of a sharply folded unsymmetrical anti
cline, the highest point, structurally.
attaining an elevation of 6640 feet
above sea level. Along its northern
edge the Madison stands nearly vertical
vi II III Plates oPtItuIiltu anu ulpEluS
south: however, a mile or less from
the Madison outcrop the beds dip at a
low angle away from the uplift. On
the south the strata also dip steeply
for a short distance from the base of
the hill, but in general the fold is
somewhat flat-topped and plunges
steeply to the eastward, disappearing
beneath younger rocks.
The anticline has a closure exceed
ing 500 feet. which is augmented by
a fault striking about n. 45 degrees
west along the axis of the closing syn
cline.
Upward Migration Favored
''The Madison or Mississippian lime
stone appears at the surface and is
about 1000 feet in thickness. OF this.
erosion has removed from 100 to 200
feet. thus permitting of a compare
lively shallow test of the underlying
Devonian, Silurian, and Carnbrian
rocks.
"Of sand or reservoir conditions the
following may be said: IN a narrow
overturned fold, such as that described.
it is quite certain that all brittle rocks
viii crush or shatter to such a degree
rs 10 not only favor the upward migra-
ton Of oil but give the necessary
porosity required as reservoir material.