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

46 ILLINOIS BASIN COAL RESOURCES
quired to clarify regional drainage relations
and the importance of pre-Pennsylvanian
deformation as a factor controlling pre-
Pennsylvanian erosion.
The regional thickening of the pre-Mc-
Leansboro deposits from the northwestern
part of the county, where they are thinnest
over the lower to middle Kinkaid upland
(T. 5 N., R. 5 E.), is to the east-southeast.
This is shown by the widening of the interval
above the middle to lower Kinkaid
upland surface segments fro~n 660 to 1040
feet in this direction. The regional thickening
from 725 to 880 feet due south along
the western border od the county across the
upper Kinkaid is less pronounced.
FIG. 6.-Photograph of a core-section of the
Caseyville conglomerate between 19,l and 1999
feet from Kingwood Oil Co., Addison Lewis
SWD-1 rotary-drill hole in sec. 9, T. 5 N., R.
7 E., Clay County.
$02) by a narrow high ~ eak in the normal
resistivity curve. As far as can be ascertained
from the isopach pattern, drainage
on this pre-Pennsylvanian surface was to
the northeast.
The previously mentioned small northwest-trending
sinkhole-like area at the
northeastern edge of the Sailor Springs
Consolidated pool may, however, ultimately
prove to be the headwaters of a branch of
the major channel to the east.
The data presented establish that the
pre-Pennsylvanian surface was modified by
erosion, producing a Kinkaid plain, which
was traversed by parallel northeast-trending
depressions. The suggestion that the dire&
tion of the drainage was to the northeast
within the county is tentative, and alternative
interpretations may be preferred since
a study of the pre-Pennsylvanian surface
throughout the Illinois basin would be re-
EXPLORATION FOR OIL
AND GAS
A certain amount of similarity in the
structure of No. 6 coal bed (PI. 3) and that
of the deeper-lying Chester beds is indicated
by the fact that the closed structural highs
and anticlinal noses coincide with the oil
pools, even the small ones. However, since
the correspondence of the coal bed structure
and the structure of the Chester beds is not
complete, and, since many more datum
points are available in Clay County for
Chester than for Pennsylvanian beds, the
coal-bed map does not represent a satisfactory
substitute for a map of the structure
of a Chester bed in the search for oil
in this county.
COAL RESOURCES
The occurrence of a considerable number
of coal beds in the Pennsylvanian deposits
of Clay County has been ascertained
from the control wells which have been
logged by the Coal Division. In the three
drill holes (Nos. 378, 402, and 495) in
which the entire Pennsylvanian sequence has
been logged, a total of 22 to 31 coal horizons
were encountered.
The coal horizons are
distributed among the Pennsylvanian groups
as follows : 11 to 18 in the McLeansboro
group, 5 to 6 in the Carbondale group,
and from 7 to 9 in the undifferentiated
Tradewater-Caseyville group^.^"
l5 See p. 11.