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" Pennsylvania Geological Survey: Trenton Black River Carbonates: Field Trip Guidebook
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Trenton and Black River Carbonates in the Union
Furnace Area of Blair and Huntingdon Counties,
Pennsylvania
A Field Trip Guidebook for the Eastern Section
AAPG Annual Meeting, September 10, 2003 and the
PAPG Spring Field Trip, May 26, 2004
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Introduction
Ordovician carbonates in central Penns Ivania
Geolo of the Union Furnace area
Petroleum geochemistry
Road log
Stop 1
StoD2
Stop 3
Acknowledgements and references
List offigures and plates
Christopher D. Laughrey, Pennsylvania Geological Survey
Jaime Kostelnik, Pennsylvania Geological Survey
David P. Gold, Professor Emeritus, Pennsylvania State University
Arnold G. Doden, Consultant, State College
John A. Harper, Pennsylvania Geological Survey
Edited by John A. Harper
Guidebook distributed by:
Pittsburgh Association of Petroleum Geologists
For information on obtaining additional copies of this guidebook, contact:
John A. Harper
Pennsylvania Geological Survey
400 Waterfront Drive
Pittsburgh, PA 15222-4745
Phone: 412-442-4230
Fax: 412-442-4298
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. . Pennsylvania Geological Survey: Trenton Black River Carbonates: Field Trip Guidebook
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. . Pennsylvania Geological Survey: Trenton Black River Carbonates: Introduction to Carbo...
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Ordovician Carbonates in Central Pennsylvania
Introd uction
Carbonate rocks of the Upper Ordovician Trenton and Black River Formations are the targets of
active petroleum exploration in western and north central Pennsylvania (Figure 6), as well as the rest
of the Appalachian basin. The potential reservoir targets are fractured dolostone or limestone traps in
narrow grabens that are related to basement structures (Avary, 2002). Although this is a seismic play
searching for structural traps, the sedimentary geology of the Trenton and Black River Formations is
also critical to exploration efforts. The distribution of porous and permeable carbonate facies
undoubtedly influenced the subsurface fairways traveled by dolomitizing fluids; in many instances
these fluids initially entered the Trenton and Black River rocks along vertical fractures related to
faulting, but then spread out laterally through permeable grainstones (Colquhoun and Trevail, 2000).
In these cases understanding the sedimentary history of the carbonates means understanding their
reservoir storage capacity. The spatial distribution of reservoir seals, reservoir compartmentalization,
and diagenetically controlled pore geometry are partially or wholly sedimentological features. The
TrentonIBlack River play is basin wide in scope, and accurate stratigraphic correlations and analyses
are necessary for rigorous petroleum exploration and development (Figure 7). Sequence stratigraphic
analysis promises to provide such correlations and analyses (Cornell and others, 2001), but robust
facies analyses must first be available before high-resolution surface and subsurface sequence
stratigraphy can be accomplished (see Pope and Read, 1997). Finally, the sedimentary geology of
the Trenton and Black River Formations has a direct bearing on understanding the petroleum source
rocks of this play, as well as the migration and accumulation of oil and gas in these rocks (Ryder and
others, 1998; Obermajer and others, 1999).
The primary purpose of this field trip is to acquaint geologists with the complex diversity of
carbonate depositional facies that characterize the Trenton and Black River Formations in
Pennsylvania. In addition to all of the reasons listed above, such an acquaintance can facilitate core
and cutting sample interpretations in subsurface work. These rocks also have been the target of
petroleum exploration here in the Valley and Ridge province. We will comment on the hydrocarbon
potential of these rocks in the deep plateau and Ridge and Valley here in central Pennsylvania. We
also wish to share with you the exciting economic geology of these rocks in this region, and hope
you find the other uses people put these carbonates to as interesting as we do. Finally, as a side
benefit to our excursion here today, we will casually examine some of the most spectacular karst
features found in Pennsylvania, and learn a little bit of history concerning some remarkable
underground explorations literally happening beneath our feet.
Setting
During Ordovician time, Pennsylvania comprised a tiny portion of the Laurentian craton, lying about
25° south of the equator (Figure 8). From Late Precambrian through Middle Ordovician time, this
region was part of an eastward-thickening, miogeoclinal basin that accommodated mostly carbonate
platform sediments (Thompson, 1999). These carbonate rocks constitute part of the "Great
American Bank" (Ginsburg, 1982) that extended more than 3,000 km (1,864 mi) along nearly the
entire length of what was the southern seaboard of the Laurentian continental mass (Figure 3). The
platform prograded eastward through Cambrian and Early Ordovician time, and its eastern terminus
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seaward was at a continental slope beyond which lay deep ocean basin sediments. Beginning in the
Middle Ordovician, the craton margin was uplifted during the Taconic orogeny (Faill, 1999). The
platform was progressively submerged. The Appalachian basin changed from a miogeoclinal
carbonate platform to an exogeosynclinal foreland molasses basin (Thompson, 1999). This basin
received large amounts of terrigenous sediment from eastern highlands, which were deposited in the
foreland basin as the Taconian clastic wedge.
The distribution of landmasses and oceans suggested for the late Middle and early Late Ordovician
(Figure 9) should have affected global seasonal weather patterns essentially the same as we
experience today (Wilde, 1991), but with the northern and southern hemispheres reversed. Summer
months feature low pressure air masses developing over large landmasses, resulting in the flow of
large amounts of moist air (monsoons). Because landmasses were essentially restricted to the
southern hemisphere at this time (figures 8 and 9), monsoons would have occurred only in that
hemisphere. Anti-trade monsoonal winds generated along the coast of Gondwana drove warmer
water northward between Siberia and Kazakhstan, countering the flow of cooler water from northern
midlatitude high pressure systems. Because Pennsylvania lay on the southwest-facing coast of
Laurentia around 25° south latitude, the dominant winds would have been trades similar to Recent
trade winds, with some variation due to continental configurations. Warm maritime air from the
Iapetan embayment between Laurentia and Siberia (figure 9) would have provided abundant rainfall
from the equator to about 35° or 40° south latitude.
The Ordovician stratigraphic record in Pennsylvania reflects the control of tectonics and
paleogeography on sedimentation (Figure 10). Lower and Middle Ordovician rocks tell the tale of
prolonged passive margin carbonate accumulation in semi-arid conditions. Upper Ordovician clastics
reveal a history of basin filling by marine and terrestrial clastics on a continental margin subjected to
moist air traveling westward in lower latitude. In between are the Upper Ordovician Trenton and
Black River Formations, and their equivalents, which were deposited during the transition from
passive margin carbonates deposited on the Great American Bank to foreland deposition of the
Taconian clastic wedge, subjected to transitional climates. These carbonate rocks developed on a
northeast-trending ramp that lay northwest of the Taconic foreland basin (Read, 1980). The Trenton
and Black River Groups of central Pennsylvania reflect the transition from carbonate shelf to ramp in
response to flexure and increasing down warping due to the growing Taconic orogeny to the
southeast. Subjacent Cambrian carbonates, the Lower to Middle Ordovician Beekmantown Group,
and the Middle Ordovician Loysburg Formation were deposited on a rimmed carbonate shelf, with
restricted circulation and wave action, on which vast peritidal and shallow water carbonate facies
flourished (Goldhammer and others, 1987; Faill, 1999). With the reversal of plate motion that
stopped the spreading of Iapetus, compressional down warping of the Laurentian continental margin
occurred as the Taconic thrust belt approached from the east. Subsidence rates increased markedly
beginning 460 ma, and marked the termination of the "Great American Carbonate
Bank" (Goldhammer and others, 1987) (Figure 11 ). This stratigraphic sequence reveals the passive
margin history of the eastern part of the Laurentian craton from Early Cambrian to Middle
Ordovician time, and the shift to down warping that led to terminal drowning of the platform during
Late Ordovician time.
Stratigraphic Nomenclature
Stratigraphic nomenclature for the Middle and Upper Ordovician rocks of central Pennsylvania is
somewhat controversial. The stratigraphic column shown in Figure 10 represents that of the
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· . Pennsylvania Geological Survey: Trenton Black River Carbonates: Introduction to Carbo...
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Stratigraphic Correlation Chart of Pennsylvania (Berg and others, 1983), with some modification
from Faill and others (1989). These authors replaced the name Nealmont Formation (Figure 7) with
the name Rodman Formation (Figure 10). The Rodman is the upper member of the Nealmont
Formation in previous schemes (see Rones, 1969 and Berg and others, 1983). Sudden, intricate facies
changes, variations in stratigraphic thickness, and poor exposures make lithostratigraphic
correlations outside of their type areas difficult. Leslie and Bergstrom (1997) showed that
biostratigraphic studies based on graptolites and conodonts, and the use ofK-bentonite beds and
sequence boundaries as stratigraphic markers helps to lessen the confusion, but serious correlation
problems within the Middle and Upper Ordovician Series still exist.
The Hatter, Snyder, and Linden Hall Formations of central Pennsylvania are equivalent to the Black
River Formation of western Pennsylvania (Figure 7). Likewise, the Nealmont, Salona, and Coburn
Formations in the outcrop are equivalent to the Trenton Formation of western Pennsylvania (.E.igy@
1). Some workers have included the Hatter, Snyder, and Linden Hall Formations of central
Pennsylvania in the Black River Group, and the Nealmont, Salona, and Coburn Formations in the
Trenton Group (Cullen-Lollis and Huff, 1986; Leslie and Bergstrom, 1997). We use these group
names in this guidebook.
K-Bentonites
Kolata and others (1996) identified and described 29 K-bentonites from the Mohawkian rocks of
central Pennsylvania. Nineteen K-bentonites are recognized and designated at the Union Furnace
outcrop along PA 453. We have identified another possible K-bentonite near the top ofthe Hatter
Formation. Cullen-Lollis (1986) and Berkheiser and Cullen-Lollis (1986) discussed the K-bentonite
occurrences here at the Union Furnace exposure. Six of the K-bentonites in the Salona Formation
have unique chemical signatures, and are particularly useful for regional correlations (Kolata and
others, 1996). Two of these, the Deicke (Eigure 12) and Millbrig K-bentonites, have been especially
useful in calibrating sequence stratigraphic correlations (Holland and Patzkowsky, 1996; Pope and
Read, 1997).
There are several useful criteria for identifying the K -bentonites in the field (Kolata and others,
1996). The K-bentonites have a soapy, waxy texture when wet. They are light to dark gray, buff,
orange, or tan in outcrop exposures. The variability is due to composition, variable oxidation due to
ground water activity, and weathering. They appear greenish gray to bluish gray to white in cores.
The K -bentonites may contain euhedral to anhedral flakes of biotite and relict glass shards. They also
might contain euhedral crystals of zircon, feldspar, and apatite. The bentonites appear like fme­
grained clay bands that might extrude under compactionalloading by the carbonate rocks, but they
weather and recess with exposure time. Chert bands in the limestones often underlie thicker
bentonites. Many bentonite layers are overgrown with trees and shrubs due to the moist, nutrient-rich
clay. The bentonite beds are stratigraphically persistent.
Geochemical fingerprinting of these bentonites involves discriminant function analysis of 26
variables (elements) and four groups (beds) (see Kolata and others, 1996). The chemistry of the
bentonite discerns a volcanic ash origin from a calc-alkaline destructive plate margin volcanic
setting.
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SYSTEM
FORMATION
SERIES
Monong.ohela Gr.
Con........ G,.
PENNSYL­
VANIAN
Gr.
Upper
DEVONIAN
Middle
Lower
Upper
SILURIAN
Lower
Upper
ORDOVICIAN
Middle
Lower
Upper
CAMBRIAN
Middle
Lower
PRE·
CAMBRIAN
D
D
•
EXPLANATION
Limestone
Mixed clastics
D
Gray shale and
siltstone
D
Dark gray to
black.hale
Mixed red clastics
•
Dolostone
Chert
Evaporites
Crystalline rocks
Figure 3.
Generalized stratigraphic column
representing the rocks exposed in the vicinity of the
field trip route.
E IN Y
\.:~~I
0 /
•
'.
'....
• ." o!i.. ,. . .. _ . ."......._
Kastle Rosources
and #2 Mahoney
'ft. _ •
•
o
•
a_ .
1
I
;_
;;
D' ....", ••.• !I
CRAWFORD
~'deSnt&a~Bal:a.dkgeal~~_:
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....... B..1<0
.. , ......, . . U..
!
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.
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ms._
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· .....
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,
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..., . '.
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;
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....
....
.(.'
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:V'
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.,
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. · .' .
!
-::- """",".-, .'I
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Cambrian outcrops
Gas in Beekmantown,
"fC' Gatesburg, or UttJe Falls
E) Dry in Trenton and deeper
' . ' .• " ' "
l '•
.",
.•. " " .
. •.' .,.' .
-'
'
•
....
SCALE
\.,.'
•• -
•• -
1
10 20 30 40 50 Miles
, ' i .. , e i ' i "
20
40
60
80 Kilometers
New wells (1999 and later)
penetrating at least the top
of the Trenton Formation
+
*
......
'\.., • EW
7.SEY
;
•• -
.',
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. .'
\;
,.'.. ••••••• , •••• ;
'" .
~
,
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Old wells (before 1999)
penetrating at least the
top of the Trenton Formation
""
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VIRGINIA
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f#1 Mann
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-
!""._._._.!unionFuma ,."
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p: II ,..I .......-"'NGTON., .•,:.,., .•".
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OHIO
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11 Manheim. 110 Orthodox,
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ell -
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IT!
Permit only - no completion
.
Gas in TrentonIBlack River
Dry in TrentonIBlack RIVer
*
011 and gas in Loysburg/Shadow Lake
Figure 6. Location of Cambrian and Ordovician outcrops, wells that penetrate the top of the Trenton Group, and new
permits for testing Trenton/Black River play in Pennsylvania. The location of the Union Furnace area is indicated.
::i
w
EASTERN
KENTUCKY
t; I SERIES
o>
EASTERN
OHIO
WESTERN
PENNSYLVANIA
I
I
WEST-CENTRAL
CENTRAL
NEW YORK
PENNSYLVANIA
I
NORTHERN
WEST VIRGINIA
UPPER
(in part)
z
c(
G I MIDDLE
:>
o
c
~I
IX
C)
I
BEL.L,EFONTE
I
ez
II
i
I '-
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w
LOWER
W
ID
rBEEKMANTOWN
BEEKMANTOWN
FM.
:E·
~
UPPER
D
PRIMARILY
DOLOSTONE
D
PRIMARILY
LIMESTONE GRAY
PRIMARILY
SHALE
PRIMARILY
BLACK SHALE
D
"ROSE RUN"
SS,
SANDSTONE
Figure 7. Regional lithostratigraphic correlation diagram for uppermost Cambrian and Ordovician rocks in the central
Appalachian basin. We will examine the Coburn through Loysburg Formations of central Pennsylvania on this field trip.
N
N
B
NP - North Polar Current
NSP - North Subpolar Current
NT - North Tropical Current
NE - North Equatorial Current
M - Monsoonal Counter-Current
SE - South Equatorial Current
ST • South Tropical Current
SSP - South Subpolar Current
SP • South Polar Current
------I.~ Warm water current
••••••• ~ Cool water current
H
Subtropical convergence
Polar convergence
Center of oceanic
high pressure
D
D
landmass
Warmwater
Cool water
Coldwater
Figure 9. Paleoceanography of Earth during the Late Ordovician (modified from Wilde,
1991). A - Southern hemisphere summer and northern hemisphere winter. B - Southern
hemisphere winter and northern hemisphere summer. Continents and seas are the same as
those in Figure L-3. The red dot is the approximate location of the Union Furnace area. B­
Balto-Scandinavia. G - Gondwana. K - Kazakhstan. L - Laurentia. S - Siberia.
"- 0
CD~
.tj
FORMATION
I!O
CD
c~
CD:
~
c:
Juniata Formation
.-.-- c:
.-....asas
ca
0)
J:
In
<
e
.-C
Bald Eagle Formation
.-0
e,)
e
~
CD
e.
e.
::)
Reedsville Formation
e
as
.e,)
0
"C
c
~
ca
0
~E
!I.I.
F
e
as
.-eas
.-
I
C
C ftI
ftI=
-Q»
.J~
-"C"C .-ecae
.:t .CD
~
>
t=
-a.
E
Milroy Mbr.
ca
J:
t.)
Bellefonte
Formation
c)
Tectonic Subsidence History
600
o
E1
~
c:
~
....,
2
D-
560
520
540
3
500
480
II',,,,
I
I
,
4-1
460
440 MA
,,
"
~~
~
I
C!)
c
580
~
"' Power Oil well
' " "RR Finch well
" Nittany Arch
,. . . . - . . . . . . - 1
"
3
, Great Valley
6 cm/1000 yr
Figure 11. Ancient Appalachian tectonic subsidence history (modified from Goldhammer and others, 1987). Note the abrupt
change in slope of the curves at approximately 460 rna. This time was the start of Black River sedimentation, and it marks
the development of the carbonate ramp in response to the Taconic orogeny.
Figure 12. Photograph of the Deicke K-bentonite at the exposure along
Pennsylvania Route 456 near Union Furnace, Pennsylvania.