MRCSP Phase I Geologic Characterization Report - Midwest ...

APPENDIX A: LOWER DEVONIAN MANDATA SHALE, LOWER DEVONIAN ORISKANY SANDSTONE
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10. LOWER DEVONIAN MANDATA SHALE
The early Devonian Mandata Shale is a thin but extensive black
shale interval within the carbonate rocks that are generally termed
the Helderberg Group or Old Port Formation in central Pennsylvania,
Maryland, and eastern West Virginia (Head, 1974) (Figure
5). In central and south-central Pennsylvania, Maryland and West
Virginia, the Mandata Shale overlies the Corriganville Limestone.
The Mandata Shale has a conformable contact with the overlying
Shriver Chert or Licking Creek Limestone (facies equivalents) in
Pennsylvania, Maryland, and West Virginia (Head, 1969, 1974),
although Dorobek and Read (1986) suggested that the Mandata is
laterally equivalent to the Licking Creek in western Maryland.
ORIGIN OF NAMES, TYPE SECTION, SIGNIFICANT
EARLIER STUDIES ON THIS INTERVAL
Swartz (1939) named the Mandata Shale for exposures 0.25 miles
south of Mandata, Perry County, Pennsylvania, on the highway to
Berrysburg.
NATURE OF LOWER AND UPPER CONTACTS
The Mandata Shale has a sharp, conformable contact with the
underlying Corriganville Limestone and grades upsection into the
overlying cherty shales of the Shriver Chert or the Licking Creek
Limestone (Glaser, 2004) (Figure 5).
LITHOLOGY
The Mandata Shale is a dark gray to black, platy to thin-bed-
ded, organic-rich shale. The shale is sparingly fossiliferous and in
western Maryland intertongues with the Licking Creek Limestone
Member of the Helderberg Group (Glaser, 2004).
DISCUSSION OF DEPTH AND THICKNESS RANGES
The thickness of the Mandata Shale ranges from 15 to 30 feet
based on outcrops and three wells in Maryland (Edwards, 1970;
Nutter and others, 1980).
DEPOSITIONAL ENVIRONMENTS/
PALEOGEOGRAPHY/TECTONISM
The Mandata Shale represents an early Devonian deepening
episode that drowned the Helderberg carbonate ramp. The ramp
became sufficiently deep to preclude carbonate deposition. This
deepening continued into and during the deposition of the Shriver
Chert and did not again shallow until the late Gedinnian Stage with
the deposition of the Oriskany Sandstone.
SUITABILITY AS A CO 2
INJECTION TARGET OR SEAL UNIT
In Maryland, there are limited analytical data to address the
Mandata’s suitability as a CO 2 sequestration target. In cooperation
with the Pennsylvania and West Virginia Geological Surveys, this
issue will be addressed in the Phase II of the MRCSP.
11. LOWER DEVONIAN ORISKANY SANDSTONE
The Oriskany Sandstone of drillers’ terminology (Figures 5 and
All-1) actually encompasses several discrete formal stratigraphic
units in the Appalachian basin (Heyman, 1977; Harper and Patchen,
1996), including: 1) the type Oriskany Sandstone of New York,
which also occurs in northwestern Pennsylvania and eastern Ohio;
2) the Ridgeley Sandstone of Pennsylvania, Maryland, Virginia and
West Virginia (where it is called Oriskany), which may or may not
be identical to the type Oriskany; 3) the Springvale Sandstone, a
basal sandstone member or sandy facies of the Bois Blanc Formation
in Ontario, northeastern Ohio, and northwestern Pennsylvania
(Oliver, 1967; Heyman, 1977); and 4) the Palmerton Formation, a
sandstone in eastern Pennsylvania that is equivalent to a portion of
the basal Onondaga Limestone (Sevon, 1968). The Palmerton will
not be discussed further herein.
ORIGIN OF NAMES, TYPE SECTION, SIGNIFICANT
EARLIER STUDIES ON THIS INTERVAL
The Oriskany Sandstone was named by Vanuxem (1839) for
its type locality in Oriskany Falls, Oneida County, New York. At
this location, the Oriskany is a white, fossiliferous quartz arenite
(Opritza, 1996; Patchen and Harper, 1996). Most of the studies
done on the formation before 1930 were for purposes of clarifying
the stratigraphic and paleontological relationships of Lower
Devonian and Upper Silurian rocks (for example, see Swartz,
1913). However, since 1930, the Oriskany has become one of the
more important formations for gas exploration in the Appalachian
basin. As a result, the Oriskany has been the subject of numerous
studies related to structure, stratigraphy, petrology, petrophysics,
and other topics. The earliest studies were performed by petroleum
geologists documenting the significant discoveries in south-central
New York and north-central Pennsylvania in the early 1930s
and 1940s (for examples, see Fettke, 1931; Torrey, 1931; Newland
and Hartnagel, 1932; Bradley and Pepper, 1938; Stow, 1938; Van
Petten, 1939). Subsequent studies by Finn (1949), Ebright and
Ingham (1951), Young and Harnberger (1955), Wood (1960),
Seilacher (1968), Heyman (1969), Patchen (1968), Jacobeen and
Kanes (1974a,b), and many others added to the general knowledge
of the formation and provided additional data on the various reservoir
properties. A resurgence of interest in this prolific reservoir in
the late 1970s and the 1980s resulted in what arguably is the most
comprehensive report produced to date on the Oriskany, the exhaustive
study done by Basan and others (1980). The most recent
reports, in the Atlas of Major Appalachian Gas Plays (Roen and
Walker, 1996), provide a summary and a single source of information
garnered from earlier studies.
NATURE OF LOWER AND UPPER CONTACTS
The Oriskany Sandstone represents a major change during Early
Devonian deposition in the Appalachian basin. The predominant
carbonate sedimentation that originated in the late Silurian ceased
or slowed, to be replaced temporarily by predominant clastic deposition.
The Early Devonian ended with a worldwide regression
that resulted in erosion throughout much of North America (the
Wallbridge discontinuity of Wheeler, 1963). This discontinuity oc-