MRCSP Phase I Geologic Characterization Report - Midwest ...

APPENDIX A: BASAL SANDSTONES TO TOP OF COPPER RIDGE INTERVAL
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Ridge is directly overlain by dolomites of the Knox Group (Beekmantown
Dolomite), making the contact very difficult to discern.
The contact is also nearly indistinguishable in western Maryland,
central Pennsylvania, and eastern West Virginia where limestones
of the Conococheague (a Copper Ridge equivalent) are directly
overlain by limestones of the Beekmantown Group (Figure 5). In
the Michigan basin (also northwesternmost Ohio, northern Indiana,
and Michigan), the contact between the Potosi Dolomite/Trempealeau
Formation (a Copper Ridge equivalent) and sandy dolomites in
the overlying Prairie du Chien Group is gradational and difficult to
differentiate.
LITHOLOGY
Tomstown/Rome/Waynesboro/lower Conasauga Formations—The
Shady or Tomstown Dolomite is a relatively consistent unit of
limestone, shale, and dolomite (Ryder and others, 1996; 1997). In
Maryland and Pennsylvania, the Shady-Tomstown consists of a calcareous
shale grading upward into thin-bedded limestone, overlain
by thick- to medium-bedded, dark gray, coarse-grained dolostone,
and overlain by massive dolostone, and interbedded limestone and
dolostone (Brezinski, 1991). The Rome and Warrior Formations
unconformably overlie the Shady-Tomstown across much of the
eastern MRCSP study area (Ryder and others, 1996, 1997). Both
the Rome and Warrior are laterally and vertically heterogeneous
in this area. The Rome Formation contains a complex sequence of
shales, siltstones, sandstones, and carbonates that is divided into
three units, in ascending order (Ryder, 1992b; Harris and others,
2004): 1) alternating thin shales and arkosic, very fine-grained to
conglomeratic sandstones. Sandstones are most common toward the
northern, fault-bounded margin of the trough as part of a thick, clastic
wedge; 2) a more consistent, shale-dominated sequence; and 3)
a 300-footthick carbonate-ramp sequence, which interdigitates and
grows thinner above the clastic wedge along the northern margin of
the trough (Ryder and others, 1997; Harris and others, 2004). East
of the Rome trough, units above the Shady-Tomstown Dolomite are
mapped as the Rome or Waynesboro Formation. The Waynesboro
is differentiated from overlying and underlying units by the presence
of red, dolomitic to anhydritic shales and can be divided in
some areas into a lower red clastic interval (red to purple shale and
sandstone), middle dolostone to impure limestone, and upper red
shale (Ryder, 1991, 1992b; Kauffman, 1999). The Rome outside of
the trough may also contains redbeds (Read, 1989a; Ryder, 1992b).
In central and western Pennsylvania, the Waynesboro also contains
coarse- to medium-grained sandstones (Kauffman, 1999). Above
the Rome Formation, within the Rome trough, the Pumpkin Valley
Shale is a gray shale and siltstone (Ryder, 1992b). The overlying
Rutledge Limestone is dominated by micritic limestone with lesser
amounts of sandy limestone and sandstone (Ryder, 1992b). The
Rogersville Shale consists of silty red and green shales and micritic
limestones, which grades north and westward into sandy shales of
the Rome Formation (Ryder, 1992b; Ryder and others, 1996, 1997).
The Maryville Limestone is a thick sequence of limestone and argillaceous
limestone that interfingers to the south and east with the
Elbrook/Honaker Dolomite. The Maryville may contain a 50- to
300-foot thick sandy interval in its lower half within the trough
(Ryder and others, 1997).
Eau Claire/Conosauga/Elbrook/Warrior Formations—In the western
portion of the MRCSP study area (eastern Indiana and Michigan),
the Eau Claire Formation (lower part of the Munising Group)
conformably overlies the basal sandstone. The Eau Claire consists
of dark gray, red, and green shales; dolomitic, feldspathic, and
partly glauconitic siltstone; very fine-grained to fine-grained,
well-sorted sandstone (often feldspathic and lithic); silty to sandy
dolostone; and oolitic limestone (Shaver and others, 1986; Catacosinos
and Daniels, 1991). Shales dominate the lower part of the
unit above the underlying Mt. Simon Sandstone, and siltstones and
silty dolostones and limestones dominate in the upper, coarseningupward
part of the unit beneath the Galesville Sandstone or Davis
Formation (Becker and others, 1978). Pore systems in the Eau
Claire are poorly developed and often filled with diagenetic feldspar,
clay minerals, dolomite and/or quartz cement . The Eau Claire
Formation intertongues eastward in central Ohio with dolostone and
dolomitic and feldspathic sandstones of the Conasauga Group. Bedding
within the Conasauga sandstones ranges from thin to medium
to massive, to interbedded with laminated and wispy, dark-gray
shale. Bioturbation (including filled vertical burrows), graded bedding,
and crossbedding are common. Dolostone are arenaceous and
ranges from light- to medium-gray and pinkish gray in color, and
from cryptocrystalline to microcrystalline to medium crystalline
in texture. Minor beds and laminae of gray to black shale, frosted
quartz grains, vugs filled with selenite and dolomite crystals, ooids,
pelloids, disseminated pyrite, laminae and thin beds of glauconite,
apatite, flat pebble conglomerate, rip-up clasts, mudcracks, and
clay-rich paleosols() are also present. Eastward toward the Rome
trough, the Conasauga Group is composed of multiple formations.
The lower part of the Conasauga in this area is restricted to the
Rome trough. The upper formations extend beyond the trough,
either pinching out laterally away from the trough or merging with
unnamed units in the Conasauga Formation. The Nolichucky Shale
is a calcareous, olive-green to gray, silty shale and siltstone (Elton
and Haney, 1974). The overlying Maynardsville Limestone is a
micritic to coarse-grained limestone, transitional between the Nolichucky
and the overlying carbonates of the Copper Ridge (Webb,
1980). The upper two thirds of the Maryville Limestone is equivalent
to the Elbrook Formation or Dolomite farther east, beyond the
southern and eastern limits of the Rome trough. The Elbrook consists
of a lower limestone, a middle, oolitic dolostone, and in some
areas, an upper sandy dolomitic limestone (Ryder, 1991; Ryder
and others, 1992b, 1996, 1997). In Pennsylvania, the Pleasant Hill
Limestone is a sandy limestone and calcareous shale grading upward
into dark-gray limestone (Berg, 1981). The overlying Warrior
Formation consists of oolitic limestone and silty to sandy dolostone
(Ryder and others, 1992b; Kauffman, 1999). Where it is thick in the
Rome trough of southwestern Pennsylvania, the Warrior may also
include a thick sequence of dolomitic sandstone overlain by darkgray
to black shale (Ryder, 1992a). In the subsurface of western
Pennsylvania, the Pleasant Hill and Warrior limestones have been
thoroughly dolomitized. This makes regional correlation difficult
on the basis of drill cuttings or cores. However, the gamma-ray and
density log signatures typically remain fairly constant despite the
change in lithology, making correlation by geophysical logs the
most preferred method.
Upper Munising/Trempealeau/Potosi/Davis/Copper Ridge/Gatesburg/Conococheague
Formations—In Michigan, the upper Munising
Group consists of the Galesville Sandstone and Franconia
Formation. The Galesville (previously Dresbach) consists of lightcolored,
fine- to coarse-grained, dolomitic sandstones. The upper
part of the unit is glauconitic (Catacosinos, 1973; Lilienthal, 1978)
and the lower part of the unit contains well-sorted quartz arenites
with thin interbeds of dolostone and green shale (Milstein, 1983).
The Galesville grades upward into the Ironton Sandstone in northwestern
Indiana with a similar distribution to the Galesville. The
Ironton consists of sandy dolostone, white, medium- to coarse-