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

62 ILLINOIS BASIN COAL RESOURCES
the beds from the trough of the Illinois
basin in Wayne County toward the southward
extension of the LaSalle anticline.
This rise continues beyond the county with
some interruptions eastward across Wabash
County, as studies in that county have
shown. The general regional rise of the
strata to the east is modified by a terracelike
flattening of the structure in a northsouth
belt one to two miles wide that extends
along a zone a little east of the center
of the county. The terrace is characterized
by some reversals in dip, and, at one position,
in T. 2 and 3 S., R. 10 and 11 E., differences
in altitude are undoubtedly the result
of normal faulting.
Albion fault zone.-This fault zone can
be traced with considerable certainty by the
use of electric logs of drill holes located
in secs. 1 and 12, T. 3 S., R. 10 E., in sec.
36, T. 2 S., R. 10 E., and in secs. 30 and 31,
T. 2 S., R. 11 E., and possibly as far north
as hole No. 138 in the SWg, sec. 18, T.
2 S., R. 14 W . The position of the fault
zone can be fairly definitely established by
noting the variation in altitude of No. 6
coal bed (or No. 5 coal bed where No. 6
is absent) (fig. 11 ) , and by noting the distribution
of drill holes in which short intervals
occur between West Franklin limestone
and Palzo sandstone, or between the Palzo
sandstone and the Glen Dean limestone of
the Chester series. In general the No. 6
coal bed west of the fault line has an altitude
of about 400-310 feet, whereas to
the east it lies 75 to 100 feet lower. The
faulting is somewhat complex, as in most
electric logs evidence of displacement is
indicated by shortening of the intervals at
more than one level, but in general these
positions are fairly closely spaced. The
fault plane dips toward the east, the fault
zones cutting across the drill holes progressively
lower from west to east. In drill
holes along the west margin of the fault
zone only the upper Pennsylvanian beds are
faulted, whereas only the Chester beds, or
at least pre-Palzo beds, are faulted in drill
holes on the east side of the zone.
The width assigned to the fault zone
represents the projection of the fault plane
onto the plane of the horizontal down to
approximately the position of the Glen Dean
formation of the Chester series.
Actual determination could be made if
the identity of the individual fault planes
could be established from hole to hole.
An approximate dip of about 60 degrees and
a throw of 125 to 150 feet seem to characterize
the displacement in the southern part
of the Albion oil pool.
The authors are aware of the presence
of a fault having a throw of more than 100
feet, which crosses the NWX of sec. 21, T.
3 S., R. 14 W., near Grayville, White
County. It may extend northeastward
across an intervening portion of Wabash
County (sec. 16, T. 3 S., R. 14 W.) and
pass into Edwards County somewhere between
drill holes Nos. 146 and 7 (secs. 9
and 17), but as there is no definite evidence
of the extension of the fault into Edwards
County, it is not mapped.
Detailed delineation of the structure of
the No. 6 coal bed is possible only where
drilling is closely spaced and where the coal
bed is present. Undoubtedly the "lay" of
the bed in those parts of the county where
the drill holes are widely spaced is actually
more irregular than can be shown from
available information.
PARALLELISM OF
PENNSYLVANIAN BEDS
The rough parallelism that characterizes
successive groups of coal beds and
limestones in the Pennsylvanian system in
the Illinois coal field is maintained in Edwards
County.
West Franklin limestone.-The West
Franklin limestone is continuous enough in
Edwards County to be mapped (pl. 5).
The structure parallels that of No. 6 coal
bed (pl. 4; table 6). By using the position
of the West Franklin limestone, the approximate
position of the "No. 7," No. 6,
and No. 5 coal beds can be fairly closely
determined.
Position of the Palzo sandstone.-Studies
of the interval between the West Franklin
limestone and the Palzo sandstone show
variations in interval and average intervals
for the various townships as follows: