MRCSP Phase I Geologic Characterization Report - Midwest ...

50 CHARACTERIZATION OF GEOLOGIC SEQUESTRATION OPPORTUNITIES IN THE MRCSP REGION
Another Middle Proterozoic rift system is found abutting the
Grenville front in southern Michigan. This feature extends, in a circular
fashion, northward through the upper peninsula of Michigan
then southward, out of the MRCSP study area, through Minnesota,
Iowa, and into Kansas. Termed the Midcontinent rift system, this
feature exhibits similar lithologies and ages (1.2-1.1 Ga) to that of
the ECRB (Daniels, 1982; Green, 1982; Van Schmus and Hinze,
1985; Dickas, 1986). However, insufficient data exist to ascertain if
these two rift systems are related (Drahovzal and others, 1992).
The Penokean province is an early Proterozoic magmatic belt that
consists of felsic and mafic volcanics (1.88-1.83 Ga) that contain
younger granitic intrusions (1.83-1.7 Ga) (Smith, 1978; Sims and
others, 1989; Van Schmus and Hinze, 1993). Penokean rocks are
found only in portions of northern Michigan within the MRCSP
study area.
Basement rocks occur at the surface in the upper peninsula of
Michigan and consist of a variety of igneous, metamorphic, and sedimentary
rocks that range from Archean to Proterozoic in age. East
of the MRCSP study area, basement rocks are exposed in the Blue
Ridge province where Grenville and Piedmont province metamorphic
rocks occur in westward-thrusted blocks of the Appalachian
mountains. Between these two areas, the basement rocks are in the
subsurface. The top of basement ranges from surface exposures in
Michigan and the Appalachians to depths that are speculated to be
greater than 45,000-feet below sea level in southeastern Pennsylvania
(Shumaker, 1996); however, no wells have penetrated nearly
that deep, thus the actually depth remains unknown.
Overall, the configuration of the basement can be seen as a bifurcating
high-area in the west that has deeper areas to the southwest,
north, and east (Figure A1-2). The shallowest areas on the map occur
in west-central Ohio and north-central Kentucky, along the Cincinnati
arch; here, basement rocks occur less than 2,000-feet below
sea level. The Cincinnati arch extends from south-central Kentucky
to west-central Ohio where it dissipates into the Ohio-Indiana platform,
a broad expanse of relatively flat-lying terrain. To the northwest,
the Kankakee arch extends across northern Indiana. Northeast
of the Ohio-Indiana platform, and on the east side of the Grenville
front, the Findlay arch, another positive structural element, occurs
and extends northeastward into Canada.
These positive features—the Cincinnati, Kankakee, and Findlay
arches and the Ohio-Indiana platform (Figures 6 and A1-2)—separate
the three major structural and sedimentary basins of this region:
the Michigan basin to the north (centered in the lower peninsula of
Michigan), the Illinois basin to the southwest (centered in southwest
Indiana, south-central Illinois, and western Kentucky), and the Appalachian
basin to the east (occurring in eastern Kentucky, eastern
Ohio, West Virginia, western Maryland, and Pennsylvania). While
subsidence was occurring in the three surrounding basins, the Cincinnati-Findlay-Kankakee
arch complex remained relatively stable
(at least compared to the rate of subsidence in the basins). However,
during the major tectonic orogenies of the Paleozoic, some structural
arching did occur and is reflected locally by the occurrence
and distribution of various lithologic facies within specific intervals
of rocks preserved in the MRCSP study area. Yet, despite this influence
of the orogenic events of the rocks, most structural relief of the
arches is thought to be the result of differential subsidence within
the basins rather than tectonic arching of these structurally positive
features (Wickstrom and others, 1992b). However, it should be
pointed out that the majority of the subsidence of the surrounding
basins occurred in the Silurian and later.
The map of the structural surface of the Precambrian (Figure A1-
2) represents its present-day configuration. The major sedimentary
basins, as known today, did not exist during the Precambrian, nor
during much of the Paleozoic. The reader will find many references,
in later sections of this report, to proto-basins (e.g., proto-Michigan
basin, etc.) meaning the early-formed portions of these basins.
Throughout the early Paleozoic, these basins developed different
configurations as the centers of deposition shifted with time (illustrated
by the thickness (isopach) maps of units with different ages)
in response to the multiple tectonic events that occurred during the
Paleozoic. Mapping the structural elements (faults, highs, and lows
as can be seen on various geologic surfaces) and the thickness of
individual units as well as combined intervals of the area, reveals the
geologic complexities of the region. Understanding these complexities
are fundamental and necessary prerequisites in order to delineate
where potential adequate, safe storage of CO 2 may be found.
A few faults cut the Cincinnati arch, Ohio-Indiana platform,
Kankakee arch and Findlay arch complex (Figure 6). One of
these faults, the Grenville front fault, extends from south-central
Kentucky, northward into eastern Michigan. In northern Ohio and
southern Michigan, this fault system is expressed as the north-south
trending Bowling Green fault system, which is locally exposed at
the surface. To the south, in west-central Ohio, however, the fault
is not exposed and a paucity of data limits our understanding of the
feature. As a result, the extent and displacement on the fault during
the Paleozoic is unknown and its position is imprecise, being based
largely on potential field data (Lidiak and Zietz, 1976; Mayhew
and others, 1982; Denison and others, 1984; Lidiak and others,
1985). Further south, the Grenville front is once again expressed
at the surface by a major fault system, the Lexington fault system,
in central Kentucky.
Several minor, northeast-oriented, down-to-southeast faults cut
the axis and southwest flank of the Kankakee arch in northern Indiana
and several northwest-trending faults cut the southeast flank of
the Findlay arch in northwestern Ohio. On regional reflection seismic
profiles in central Ohio, deep basement reflectors can be seen
dipping to the southeast. To the east, in east-central Ohio, a zone of
indistinct reflectors is present, while west-dipping reflectors occur
in the basement of eastern Ohio. The transition zone between the
southeast- to west-dipping reflectors is called the Coshocton zone
(Figure 6) and is thought to represent an ancient continent to continent
suture zone (Culotta and others, 1990).
North of the Kankakee arch and west of the Findlay arch, the
Michigan basin forms a nearly circular depression that reaches a
depth of more than 15,000-feet below sea level (Warner, 1989). The
configuration of the basin is largely based on oil and gas test wells
because little publicly available seismic data exist for the region.
Because of this, little is known of deep basement faulting in the
basin. The Mid-Michigan rift part of the Midcontinent rift system
(Figure 6) has been mapped largely on potential field data and is interpreted
to form a Precambrian graben that extends northwestward
across the basin (Hinze and others, 1971, 1975, 1997; Brown and
others, 1982).
South and southwest of the Kankakee arch, basement of the
MRCSP study area dips southwest onto the northeast edge of the
Illinois Basin, a feature that covers most of Illinois, southwestern
Indiana and western Kentucky. The southwest dip is fairly regular at
a rate of about a half of a degree (Buschbach, 1984; Rupp, 1991).
To the east of the Cincinnati-Findlay arch is the Appalachian
basin. The basement dips at an average rate of about one degree to
the southeast in the Ohio part of the basin (Baranoski, 2002). Much
of the basement configuration for Ohio is based on oil and gas well
data, backed up by about 600 miles of publicly available reflection
seismic data.