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

42 ILLINOIS BASIAT COAL RESOURCES
West Franklin limestone to No.6 coal bed 0 Producing well [rotary) Closely- spaced control area
m. 100'-150' 9- Dry hole (rotary); +Dry hole 0 Shoal Creek limestone missing
I' 15150'-200' 305 County number ~lsopach showing interval from No.6
rn 2&-235' X Hole partially logged by Survey coo cool bed to Shool Creek limestone
FIG. 3.-Distribution in Clay County of nTest Franklin limestone where it produces characteristic
pattern in electric logs, variations in interval between West Franklin limestone and No. 6 coal
bed, and variations in interval between Shoal Creek limestone and No. 6 coal bed.
INTERVAL BETWEEN THE SHOAL CREEK
LIMESTONE AND NO. 6 COAL BED
The interval between Shoal Creek limestone
and No. 6 coal bed ranges from 283 to
455 feet within the co,unty (fig. 3). It is
least in the northwestern part of the county
and increases fairly uniformly to the southeast
across the basin flank. Within the basin
floor area the interval increases irregularly
to the southeast, with a maximum interval
of 155 feet being recorded near the center
of the south line of the county. The interval
decreases locally and slightly over
the Clay City anticline in the southeastern
part of the county. In general the local
variation in interval appears to be related
to the variations in thickness of a psominent
sandstone which overlies the West Franklin
limestone.
INTERVAL BETWEEN THE WEST
FRANKLIN LIAIESTONE AND
No. 6 COAL BED
The typical West Franklin limestone is
present only in scattered areas in Clap
County (fig. 3). In such areas the interval
between it and No. 6 coal bed ranges from