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

114 ILLINOIS BASIN COAL RESOURCES
COUNTY NO 56
PURE-MILLER NO I
SEC Z.T3N .R 9E
in the Parkersburg Pool in secs. 29 and 30,
T. 2 N., R. 14 W.
A thin coal bed, capped by 1 to 4 feet
of black "slate," commonly lies 10 to 15
feet above the upper bed of the West Franklin
limestone (fig. 28)) with shale and silty
shale intervening. This coal bed has the
position of the Ditney coal bed of southwestern
Indiana and Wabash County,
Illinois.' It is absent in the west tier of
townships in Richland County; there a
higher sandstone cuts across the position of
the coal bed and extends down to the West
Franklin limestone. The coal bed was found
in all drill holes logged by the Survey in the
eastern part of the county. The Ditney coal
bed has not been definitely recognized in
electric logs in areas where only a single
bench of limestone is present.
Underlying the West Franklin limestone
there is commonly 5 to 10 feet of variegated
shale, dark red, green, yellow, and gray.
In three of the nine control drill holes (Yes,
1, 5, 6, fig. 28) this variegated shale was
j Vctller. R. I,.. Ditnev folio. Tncliana: U. S. Geol. S~lrvey,
Geol. .Atlas, Folio 84, p. 2, 1902.
absent. Generally it is one of the most
diagnostic beds in the Pennsylvanian succession.
The cuttings resemble underclay,
being very soft with poorly defined or no
bedding planes and with slip-fracture surf
aces.
The West Franklin limestone is one of
the best stratigraphic markers or key beds
in the Pennsylvanian system in Richland
County, because it was absent in only
ten drill holes, all in the southwestern part
of the county (Ts. 2 and 3 N., Rs. 8 and 9
E.), and was therefore selected as a structural
datum plane (pl. 1 I). Because it is
thought to be more persistent, the lower
bench is regarded as most suitable to use
for this purpose when two benches are reported
or are indicated by the electric log
pattern. Reference is to the top of this bed.
"No. 7" coal bed.-A coal bed probably
rarely as much as 3 feet thick is widespread
in the county 40 to '70 feet above No. 6
ccal bed. It is overlain by 2 or 3 feet of
black "slate" which, together with the coal
bed, produces a distinctive pattern, ordinvi1.i-
consisting of a small normal re-