subsurface geology and coal resources of the pennsylvanian system ...

with respect to the No. 6 coal bed and the
West Franklin limestone is similar to that
of the limestone outcropping near a locality
known as Reel's Corners northwest of Mt.
Carmel near the center sec. 8, T. 1 S., R.
12 W.This appears to be the most continuous
and characteristically developed
group of beds in the control drill holes above
the ?Vest Franklin limestone in Edwards
County. In the electric logs its position
is generally indicated by low resistivity
peaks in both normal and third curves.
In drill hole No. 7 (fig. 10) what appears
to be the same thin limestone noted in the
preceding paragraph was encountered only
about 475 feet above No. 6 coal bed. A
thick bed of limestone (15 feet) was penetrated
about 50 feet lower-possibly the
Shoal Creek. Such a stratigraphic arrangement
is strongly suggestive of shortening by
faulting between the West Franklin and
Reel limestone, although faulting is not
generally suspected in this area.
Of the seven control drill holes which
show the geologic succession above the thin
limestone noted in the two preceding paragraphs,
several show a number of thin limestone,
coal, and black shale beds at different
positions. Because the records of the cuttings
of these drill holes lack uniformity of
arrangement, it has not been possible to
correlate the beds. Some of the drill holes
penetrated beds 700 to 800 feet above No.
6 coal bed, and it seems probable that such
members of the McLeansboro group as the
Friendsville coal bed and the Millersville
(and possibly even the Omega) limestone
may be represented.
Electric logs of drill holes in the same
pool display a similarity of pattern above
the position of the West Franklin limestone
that indicates continuity of certain relatively
thin layers, but correlation over the entire
county and with definite beds encountered
in control wells has not been very satisfac-
tory. Usually the surface casing of the
drill holes in the Illinois basin extends to
some fairly persistent and relatively thick
limestone bed, but this does not seem to be
the case in Edwards County.
EDWARDS COUNTY 59
Beds below the West Franklin limestone.-The
usual monotonous succession
of shale and siltstone beds lying between the
West Franklin limestone and "No. 7" coal
bed includes in some places beds of sandstone
(No. 3, fig. 9), the positions of which are
marked by opposite peaks in the normal and
curves. In four control wells
(Nos. 3, 5, fig. 9; Nos. 6, 7, fig. 10) a thin
bed of limestone was reported about 150
feet above the base of the McLeansboro
group. It is unaccompanied by black shale
or a coal bed. The somewhat remote possibility
that the limestone at this position in
drill hole No. 6 (fig. 10) may represent
the lower bench of the West Franklin limestone
has been mentioned.
In five control drill holes (Nos. 1, 34,
fig. 8; Nos. 2, 3, fig. 9; No. 7, fig. 10) a
limestone 5 feet or less in thickness was encountered
from 5 to 35 feet below the
"No. 7" coal bed. Well cuttings are described
as buff to brown, and as dense to
argillaceous in texture and composition.
The bed is underlain by shale, siltstone, or
sandstone, and not by the sequence of black
shale and coal beds usually found beneath
Pennsylvanian limestones. The position
and relationship are those characteristic of
the Bankston Fork limestone of Saline
C~unty.~ The Bankston Fork limestone is
found throughout a wide area in southern
Illinois, but it is by no means continuous,
for it is known to pinch out within short
distances from an area of average thickness.
In electric logs its position is usually marked
by its relatively high resistivity and low
potential strength, a short distance belo,w
"No. 7" coal bed.
Between the Bankston Fork limestone
and the Herrin limestone (see control drill
holes Nos. 11, 34, fig. 8 ; Nos. 2, 91, fig. 9;
Nos. 7, 8, 106, fig. 10) there is commonly
a massive sandstone member thought to be
the equivalent of the Anvil Rock sandstone
of western Kent~cky,~ which is also widely
distributed in Saline and Gallatin counties
in Illinois. This sandstone in places rests
upon an uneven eroded surface which cuts
down into, and even across, the Herrin
Cady. G. H., Areal geology of Saline County: Trans.
O "No. 19. Hard bituminous limestone 1 to 3 feet." Illinois Arad. Sci. vol. 19. p. 261, 1927.
A. If. Worthen, Geol. Survey of Illinois, vol. VT, p. 56, 1875. Owcn, D. D., Kentucky Geol. Survey, vol. 1, 1856.