Geology Reference
In-Depth Information
Fig. 16.2
Stratigraphic column of the Pennsylvanian (Late
Carboniferous) Period in the EIB and WIB. The Morrowan and
Atokan Stages are largely absent from the WIB. Stratigraphic
intervals studied in the WIB include:
w1
: Ireland Sandstone,
w2
: Tonganoxie Sandstone,
w3
: Noxie Sandstone,
w4
: Englevale
Sandstones, and
w5
: Cherokee Group. In the EIB, the stratigraphic
intervals include:
e1
: Herrin Coal/Energy Shale,
e2
: Springfield
Coal/Dykersburg Shale,
e3
: Colchester coal/Francis Creek
Shale,
e4
: Murphysboro Coal,
e5
: Western Kentucky No. 4 coal,
e6
: Elm Lick coal,
e7
: Abbott Formation,
e8
: above Lower Block
coal,
e9
: Hindostan whetstones,
e10
: above Caseyville incised
valley,
e11
: upper Caseyville incised valley-fill sequence
an unconformable base and fill incised paleovalleys
(IVFs), which are cut down from the more regionally
extensive paleosols (Feldman et al.
1995
). In the lower
Pennsylvanian, the valley-filling sandstones of the EIB
may be more than 60 m thick (Potter and Desborough
1965
). Valley fills are complex but conglomeratic
sandstones, with extrabasinal quartz pebbles are
common (Sedimentation Seminar
1978
; Greb et al.
1992
;
Archer et al.
1994
; Archer and Greb
1995
). Younger
paleochannel sandstones in both basins may also con-
tain extrabasinal quartz clasts, but to a lesser extent than in
the lower Pennsylvanian. Lithoclasts in Middle and
Upper Pennsylvanian incised sandstones commonly
contain intrabasinal lithologies, with limestone,
shale, and sideritic clasts being the most abundant.
Quartzarenites dominate the Lower Pennsylvanian,
while litharenites and sublitharenites dominate the
Middle and Upper Pennsylvanian. Carbonized plant
material is locally abundant and ranges in size from
large, fossil-tree trunks down to sand-sized material
(“coffee grounds”). Sandstone bodies can exhibit an
elongate trend, mostly south to southwest, and have
been historically described as “shoestring sands” (Bass
1934, 1936
; Potter
1962
). Sandstone units typically
fine upward into heterolithic strata or gray shale that
lack fossils of marine macroinvertebrates. The shale
