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PALAIOS, 2019, v. 34, 405–423
Research Article
DOI: http://dx.doi.org/10.2110/palo.2019.020
SEDIMENTOLOGY AND CARBON ISOTOPE (d13C) STRATIGRAPHY OF SILURIAN–DEVONIAN
BOUNDARY INTERVAL STRATA, APPALACHIAN BASIN (PENNSYLVANIA, USA)
ANYA V. HESS1, 2AND JEFFREY M. TROP1
1Department of Geology and Environmental Geosciences, Bucknell University, Moore Avenue, Lewisburg, Pennsylvania 17837, USA2Department of Geological Sciences, Rutgers University, Piscataway, New Jersey 08854, USA
email: [email protected]
ABSTRACT: Silurian–Devonian boundary interval strata deposited during the expansion of land plants record a majorperturbation of the carbon cycle, the global Klonk Event, one of the largest carbon isotope excursions during thePhanerozoic. In the Appalachian Basin, these marine strata record the regional buildup to the Acadian Orogeny. Thisstudy reports new sedimentologic, paleontologic, ichnologic, and carbon isotope data from an exceptional quarryexposure in central Pennsylvania, USA, a historically understudied area between better-documented outcrops.500 km away to the southwest (West Virginia, Virginia, Maryland) and northeast (New York). Facies spanning thecontinuous 113-m thick outcrop are dominantly carbonate and fine-grained siliciclastic strata interpreted as beingdeposited in supratidal through subtidal environments, including oxygen-limited environments below storm wavebase. They record parts of three transgressive-regressive cycles, in the (1) upper Silurian Tonoloway Formation,(2) upper Silurian–Lower Devonian Keyser Formation through lower Mandata Member of the Old Port Formation,and (3) Lower Devonian Mandata through Ridgeley Members of the Old Port Formation. Micrite matrix d13Ccarb
analyses exhibit a large, positive d13Ccarb excursion (.5% amplitude). Outcrops of this interval in the AppalachianBasin occur in two belts, between which correlation has been historically challenging. The regional correlationpresented herein is based on carbon-isotope trends and is more consistent with published conodont biostratigraphyand volcanic ash ages, an improvement over published correlations based on lithostratigraphy. Transgressive-regressive trends at the central Pennsylvania study site are not consistent with regional trends, indicating that localcontrols (tectonics, sediment supply) rather than global (eustasy) dominated depositional patterns in the Silurian–Devonian boundary interval in the Appalachian Basin.
INTRODUCTION
The Silurian–Devonian transition was a time of major change in the
global biosphere. Vascular land plants had evolved by the late Silurian and
diversified rapidly in the Devonian. In the late Silurian–Early Devonian,
arthropods transitioned to land and impacted soil development (Kenrick et
al. 2012). These changes coincided temporally with an overall increase in
atmospheric oxygen that led to a peak in atmospheric oxygen content
(Lenton et al. 2016; Lu et al. 2018). In the Appalachian Basin, the
Silurian–Devonian boundary interval has recently been the focus of
renewed interest as the advent of modern techniques (uranium-lead
geochronology, carbon isotope chemostratigraphy) allows for more
advanced, quantitative analysis (Kleffner et al. 2009; Husson et al. 2016;
McAdams et al. 2017).
A major perturbation to the carbon cycle, the Klonk Event, is also
recorded at the Silurian–Devonian boundary, as a significant carbon
isotope excursion. Carbon isotope analyses of bulk marine carbonates
(d13Ccarb) document a positive carbon isotope excursion as much as 7% in
amplitude, making it one of the largest such excursions during the
Phanerozoic. The excursion has been documented in sections around the
world: the United States in the Great Basin of Nevada and Utah (3.0%;
Saltzman 2002, 2005) and the Arbuckle Mountains of Oklahoma (3.3%;
Saltzman 2002); the Czech Republic and France (3.8–4.0%; Buggisch and
Mann 2004; Buggisch and Joachimski 2006); and Ukraine (.6%;
Malkowski et al. 2009). The similar shape and magnitude of the d13Ccarb
excursions has led previous workers to argue that it represents a
perturbation to the global carbon cycle, with rising values in d13Ccarb
representing the evolving isotopic composition of global dissolved
inorganic carbon (d13CDIC). Proposed drivers of the Klonk Event include
global regression and the weathering of exposed, isotopically heavy
Silurian carbonate platforms (Saltzman 2002) or enhanced burial of
organic carbon from newly evolved terrestrial biota (Malkowski and Racki
2009). However, coupled chemostratigraphic-sedimentologic studies
spanning Silurian–Devonian strata needed to evaluate these potential
drivers are generally lacking.
The carbon isotope excursion has been of recent interest in the
Appalachian Basin, where it was originally documented in West Virginia
(7%; Saltzman 2002; Husson et al. 2016) and more recently in New York
(Husson et al. 2016). However, there still exists a geographic gap of .500
km between Appalachian Basin sites (Fig. 1). The Silurian–Devonian
boundary interval has been understudied in most of Pennsylvania,
particularly with regards to modern methods, for a number of reasons.
Temporally, the period boundary is a natural stopping point, and many
studies are restricted to either Silurian (e.g., Smosna and Patchen 1978;
Brett et al. 1990; Bell and Smosna 1998; McLaughlin et al. 2012) or
Devonian strata (e.g., Diedrich and Wilkinson 1999; Ver Straeten 2007,
2008; Ver Straeten et al. 2011). Geographically, outcrops occur in two
belts, a northern belt in New York and parts of New Jersey and
northeastern-most Pennsylvania, and a southern belt spanning the Virginia-
West Virginia border, the western tip of Maryland, and southern and central
Pennsylvania (Fig. 1). Outcrops in central Pennsylvania are generally poor
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since they are less resistant to weathering. Many previous studies are
restricted to either the New York-New Jersey part of the northern outcrop
belt (e.g., Epstein et al. 1967; Kleffner et al. 2009) or the Virginia-West
Virginia-southernmost Pennsylvania part of the southern outcrop belt (e.g.,
Dorobek and Read 1986); herein, the terms ‘northern outcrop belt’ and
‘southern outcrop belt’ refer to these areas that have been historically well
studied. Regional correlations have been published for the southern
outcrop belt (Dorobek and Read 1986) and for the northern outcrop belt
(Rickard 1962; Epstein et al. 1967; Laporte 1969). Nomenclature and
facies changes between the two outcrop belts make correlation difficult,
and no basin-wide correlation scheme has been universally adopted (e.g.,
Smosna 1988).
An exceptional, continuous quarry exposure of Silurian–Devonian
boundary interval strata near the town of Winfield in central Pennsylvania
(herein referred to as Winfield Quarry; Figs. 1, 2) provides a unique
opportunity to fill the temporal and geographic gap. The purpose of this
study is to (1) document the sedimentology, paleontology, and lithostratig-
raphy of Winfield Quarry strata in order to reconstruct depositional
environments and relative sea-level change, (2) document the chemo-
stratigraphy and carbon isotope excursion in the context of that detailed
sedimentology, paleontology, and stratigraphy, and (3) use the chemo-
stratigraphic-lithostratigraphic framework to improve regional stratigraphic
correlations and provide additional constraints on a major perturbation to
the ancient geologic carbon cycle.
GEOLOGIC SETTING
Paleogeographic and Tectonic Setting
The Appalachian foreland basin, shaped by plate convergence, spanned
much of eastern North America throughout most of the Paleozoic. During
the late Silurian–Early Devonian, the basin was at ~308S latitude (Kent
and Van Der Voo 1990; Witzke 1990), making it an environment
conducive to carbonate deposition. The foreland basin first formed in the
Middle Ordovician, when the Taconic orogeny marked initial closure of the
Iapetus Ocean and collision of an island arc with eastern Laurentia.
Taconic deformation in New England was most intense from ~496 to
~428 Ma, with metamorphism and roughly coincident development of the
foreland basin ranging from ~480 to ~455 Ma in the southern
Appalachians and New England (Hatcher 2010 and references therein).
The Silurian–Devonian transition in the Appalachian Basin was a time
of diminished clastic input that allowed marine organisms to flourish,
resulting in a variety of carbonate facies throughout the basin (e.g., Laporte
FIG. 1.—Map of the eastern United States showing outcrop belts of Silurian–
Devonian boundary interval strata (compiled from King et al. 1974; Denkler and
Harris 1988; Miles 2003; Kleffner et al. 2009). Circles indicate sites of existing
carbon isotope studies from this interval.
FIG. 2.—Photograph of the quarry exposure at Winfield, Pennsylvania, described in section WQ1. Dashed black lines indicate approximate formation boundaries.
Abbreviation: Fm. ¼ Formation.
A.V. Hess and J.M. Trop406 P A L A I O S
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1969; Dorobek and Read 1986). In the central Appalachians, where this
study focuses, the late Silurian through Early Devonian historically has
been considered a time of tectonic quiescence between the Taconic and
Acadian orogenies (Rodgers 1967; Johnson 1971; Dorobek and Read
1986). However, some researchers have suggested that Acadian orogenesis
began as early as the late Silurian and would therefore have coincided with
deposition of the strata discussed herein (Ebert and Matteson 2003; Ver
Straeten 2007).
During the Acadian orogeny, a series of terranes collided with the
northern part of the eastern margin of Laurentia. This transpressional,
zippered collision progressed southward through time, affecting areas from
present-day Newfoundland through Georgia. It culminated in the closure of
the Rheic ocean when Baltica (present-day Europe) collided with Laurentia
in the early part of the Mississippian (~345 Ma) (Ver Straeten 2009;
Hatcher 2010 and references therein).
Stratigraphy
The exposure at Winfield Quarry includes the upper Silurian Tonoloway
Formation, upper Silurian to Lower Devonian Keyser Formation, and
Lower Devonian Old Port Formation (Fig. 3). These formation
designations have been adopted from Inners (1997), the most detailed
existing study of upper Silurian–Lower Devonian strata in central
Pennsylvania. The Keyser Formation is divided into the Byers Island,
Jersey Shore, and La Vale Members (Head 1969). The Old Port Formation
is divided into the New Creek-Corriganville, Mandata, and Ridgeley
Members (Inners 1997). Stratigraphic nomenclature used in Pennsylvania
for this interval is broadly similar to that used throughout the southern
outcrop belt but differs significantly from that used in the northern outcrop
belt (Fig. 3).
The Tonoloway Formation consists of evaporitic shelfal carbonates and
is correlative in the subsurface to thick halites and anhydrites in West
Virginia and New York (Smosna et al. 1976; Mount 2014). Strata
immediately overlying the Tonoloway are regionally referred to as the
Helderberg Group, but this can be problematic for correlation as the term
encompasses different formations and members in the southern and
northern outcrop belts (Fig. 3) (e.g., compare Rickard 1962 with Dorobek
and Read 1986), and the term is not used herein.
In West Virginia, Virginia, and Maryland, the contact between the
Keyser and Tonoloway Formations is unconformable at the basin edges
and conformable in the basin center. The Keyser Formation is broken into
three members (Fig. 3). Lowermost is the Byers Island Member, which
consists of fossiliferous, nodular carbonates. The overlying Jersey Shore
Member contains a variety of carbonate facies with diverse fossil
assemblages but is distinguished by its abundant coral-stromatoporoid
buildups along the basin margins. Finally, the La Vale Member is a
laminated, mudcracked carbonate with minor stromatoporoid biostromes
(Head 1969).
FIG. 3.—Stratigraphic correlation chart for upper Silurian–Lower Devonian strata throughout the southern and northern outcrop belts of the central Appalachian Basin.
Bold text indicates formations, italicized text indicates members, plain text indicates not specified, from source publications. Abbreviation: Grp.¼ Group.
SEDIMENTOLOGY AND ISOTOPE STRATIGRAPHY OF SILURIAN–DEVONIAN STRATAP A L A I O S 407
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In the southern outcrop belt, the Byers Island Member is termed the
lower Keyser Formation (Fig. 3) and is aggradational open-marine
carbonates with skeletal banks around the basin edges and bioturbated,
nodular carbonates toward the basin center. Skeletal banks consist of coral-
stromatoporoid mud mounds and framestones. The middle part of the
Keyser Formation in West Virginia is regressive Clifton Forge sandstones
on the eastern basin margin and grades basinward into the Big Mountain
shale and correlative skeletal carbonates (Dorobek and Read 1986). These
clastic units do not extend into Pennsylvania (Head 1969) and their
correlation to the carbonate succession there is ambiguous (e.g., compare
Head 1969 and Dorobek and Read 1986). The La Vale Member is
equivalent to the upper Keyser Formation in the southern outcrop belt,
which consists of transgressive skeletal carbonates and contains coral-
stromatoporoid mud mounds and framestones (Dorobek and Read 1986).
The Old Port Formation consists of four members in Pennsylvania, in
stratigraphic order from oldest, the New Creek-Corriganville, Mandata,
Shriver, and Ridgeley Members (Inners 1997) (Fig. 3). The New Creek
Member consists of regressive skeletal banks. The Corriganville Member
is a transgressive cherty carbonate. The Mandata and Shriver Members are
transgressive basinal shales and transgressive-to-regressive cherty carbon-
ates, respectively. The Ridgeley Member is a basin-wide sandstone that
represents the first substantial influx of clastic sediment resulting from the
Acadian Orogeny in the central Appalachian Basin (Dorobek and Read
1986).
Outside of Pennsylvania, the term Old Port Formation is not used and its
members correspond to named formations. In Maryland, the New Creek
Formation interfingers with the uppermost Keyser Formation and is
equivalent to the Elbow Ridge sandstone at the eastern edge of the basin.
The Corriganville Member is equivalent to the Healing Springs sandstone
at the eastern edge of the basin in Virginia. The Mandata and Shriver
Members are equivalent to cherty carbonates of the Licking Creek
Formation nearer the basin margin in the southern outcrop belt. Outside of
central Pennsylvania, the Ridgeley Member is equivalent to the Oriskany
Formation.
The northern outcrop belt is oriented parallel to depositional dip, with
more proximal facies to the west. Facies are time transgressive and timelines
typically span multiple formations or members (Rickard 1962; Laporte
1969; Husson et al. 2016). The Cobleskill Formation (Fig. 3) consists of
massive, fossiliferous carbonates, including stromatoporoids and corals, and
grades westward to less fossiliferous, thin-bedded dolomites. The Rondout
and Manlius Formations represent a transgressive-regressive cycle consist-
ing of shallow-water stromatolites and stromatoporoid-coral biostromes and
bioherms and associated lagoonal facies (Rickard 1962; Laporte 1969;
Belak 1980). The Coeymans, Kalkberg, and New Scotland Formations are
progressively deeper water facies, transitioning to open marine by the
Kalkberg and New Scotland Formations (Laporte 1969).
Regional Stratigraphic Correlations
The units discussed above have been correlated thus far mainly using
lithostratigraphy (Fig. 3). The Keyser Formation is typically correlated in
the northern outcrop belt to portions of the Cobleskill, Rondout, and
Manlius Formations, and the Old Port Formation is typically correlated to
portions of the Manlius, Coeymans, Kalkberg, and New Scotland
Formations (Head 1969; Laporte 1969).
Conodont biostratigraphy, volcanic ashes, and carbon isotope stratigra-
phy have also aided correlation of this complicated stratigraphy. Based on
the first occurrence of the conodont Icriodus woschmidti, the Silurian–
Devonian boundary has been placed in the upper Keyser Formation in
Virginia and West Virginia (Helfrich 1978; Denkler and Harris 1988). In
the northern outcrop belt, it has been variously placed in the Rondout
Formation (Denkler and Harris 1988), the lower Coeymans Formation
(Tucker et al. 1998), and either within the Manlius Formation or between
the Coeymans and Kalkberg Formations (Kleffner et al. 2009, using
combined biostratigraphy and carbon isotope stratigraphy).
Volcanic ashes (bentonites) have been used to correlate the Silurian–
Devonian strata over limited distances (e.g., Rickard 1962; Smith and Way
1988). In the southern outcrop belt, Smith and Way (1988) first described a
set of three ash beds that occur in the Corriganville (Bald Hill Bentonites A
and B) and Mandata (Bald Hill Bentonite C) Members of the Old Port
Formation at the type section near Hollidaysburg, Penn., 84 miles west-
southwest of Winfield Quarry. In the northern outcrop belt, the Kalkberg
Bentonite, an ash bed in the New Scotland Formation, has been dated by
McAdams et al. (2017) using U-Pb analysis of zircons, placing it in the
middle Lochkvian (Early Devonian) at 417.6160.12 Ma. Smith and Way
(1988) correlated this bed to their Bald Hill Bentonite A in the
Corriganville Member of the southern outcrop belt. McAdams et al.
(2017) note, however, that the number of volcanic ash beds in the Lower
Devonian of the Appalachians makes correlation of individual beds
potentially problematic.
Carbon isotope stratigraphy was recently used by Husson et al. (2016) to
correlate between a section in West Virginia and four sections in New York.
Their correlation shows that facies and the stratigraphic packages based on
them are diachronous across the basin, that the Keyser Formation is
correlative with the Rondout, Manlius, and parts of the Coeymans
Formations of New York, and that the New Creek-Corriganville Members
are correlative with the Kalkberg, New Scotland, and Becraft Formations
of New York. The Winfield Quarry section provides an opportunity to
refine this correlation between the northern and southern outcrop belts.
Field Site
The field site for this study is a quarry approximately 2 km west of
Winfield, Pennsylvania, in Union County (N 40.898168, W 076.893078)
(Fig. 2). It was active a few years prior to the data collection phase,
providing a fresh rockface. It was inactive during the data collection
phase of this project (2007) and has since been reopened; the base of the
original section has been removed. A well-exposed stratigraphic section
(WQ1) was measured on a bed-by-bed basis using a Jacob’s staff at the
west end of the quarry. Refer to Hess (2008) for an additional, less
extensive section spanning only the Old Port Formation. The stratigraphic
section and geochemical data from the western exposure are discussed
herein.
Geochemical Methodology
A total of 63 micrite samples were analyzed from the lower 88 m of the
WQ1 section, spanning the Tonoloway Formation through the Shriver
Member of the Old Port Formation. Only samples devoid of fossil
fragments, fractures, and veins were selected. Rock samples were broken
using a rock hammer in a cleaned room to provide a fresh surface. Powder
was extracted from this surface using a Dremel drill with a diamond-dust-
coated drill bit, while continually monitoring to ensure no material other
than micrite was sampled. Powder was deposited and sealed directly into
glass vials. Between samples, the rock hammer and drill bit were sanitized
using a solution of 10%-diluted hydrochloric acid.
Isotope analyses were conducted in the Stable Isotope Ratios in the
Environment, Analytical Laboratory (SIREAL) in the Department of Earth
and Environmental Science at the University of Rochester. Samples were
pretreated with 30% H2O2 to remove organic material, followed by three
rinses with deionized water and a final rinse with methanol. Analyses were
run on a Thermo Electron Corporation Finnegan Delta plus XP mass
spectrometer in continuous-flow mode via the Thermo Electron Gas Bench
peripheral and a GC-PAL autosampler. Samples were loaded into 4mL tubes
with pierceable, self-healing rubber septa with PTFE liners. Tubes were then
flushed with UHP helium at about 100 mL/minute for 10 minutes.
A.V. Hess and J.M. Trop408 P A L A I O S
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100% phosphoric acid was injected through the septum manually with a 16-
gauge needle and syringe. All samples were vortexed to insure complete
mixing of the sample and the acid. Tubes were loaded into a block heated to
708C. Samples reacted for at least 45 minutes but never more than 12 hours
before they were analyzed. Carbon dioxide gas evolved from the reaction
with the acid was then drawn into the instrument for analysis. Carbon and
oxygen isotopic results are reported in permil relative to VPDB (Vienna Pee-
Dee Belemnite) and normalized (Coplen 1994) on scales such that the
carbon and oxygen isotopic values of NBS-19 are 1.95 permil and -2.2
permil, respectively, carbon and oxygen isotopic values of NBS-18 are -5.01
permil and -23 permil, respectively, and the carbon isotopic value of
L-SVEC is -46.6 permil. Average precision (1-sigma) is 0.06 and 0.10 for
carbon and oxygen isotopes, respectively. For repeat analyses, the average of
the carbon and oxygen isotope values is discussed herein.
SEDIMENTOLOGY
Facies
Sedimentary facies are defined on the basis of lithology, sedimentary
structures, paleontology, and ichnology, particularly as they relate to the
interpretation of depositional environments. Winfield Quarry strata consist
of four lithologies: micrite, biomicrite and biosparite, sandy intrabiosparite,
and shale. Seven sedimentary facies representative of different depositional
environments are identified on the basis of lithology, sedimentary
structures, ichnofabrics, and fossils (Table 1, Figs. 4, 5). See Hess
(2008) for additional photographs of facies and fossils.
Massive Micrite Facies (F1a).—The massive micrite facies is
characterized by a lack of fossils and physical sedimentary structures,
though some instances contain low-diversity, high-abundance ichnologic
assemblages of Chondrites and Zoophycos trace fossils (Fig. 4A, 4B). The
majority of this facies is interpreted as having been deposited in low-
energy, subtidal environments below storm wave base. The lack of body
fossils indicates an inhospitable environment. Zoophycos has been linked
to low-oxygen, though not entirely anoxic, conditions (Marintsch and
Finks 1978; Bromley and Ekdale 1984), especially when they occur in high
abundance and low diversity, as here. While Chondrites and Zoophycos
traces in more recent deposits occur in deep water, Paleozoic strata with
these traces can have formed in a variety of water depths, from lagoonal to
below storm wave base (Ekdale 1988; Frey et al. 1990). On the basis of its
thickness (~20 m) and association with relatively deep water under- and
overlying units, the package of this facies with Chondrites and Zoophycos
traces is interpreted as having been deposited below storm wave base, in
oxygen-limited conditions (Fig. 6). For micrites lacking trace fossils, their
environmental interpretation is based on the sedimentology and paleon-
tology of interbedded lithofacies, with some units deposited in waters
potentially as shallow as the intertidal zone. Refer to the Inferred
Depositional Setting and Relative Sea-Level Fluctuations section for more
details.
Micrite with Sedimentary Structures Facies (F1b).—The micrite
with sedimentary structures facies is characterized by the presence of
physical and organic sedimentary structures including mudcracks,
evaporites, heterolithic bedding, intraclasts, sparse fenestrae, stromato-
lites, and cryptalgal laminae (Fig. 4C–4F). Stromatolites and cryptalgal
laminae are domal on a millimeter to decimeter scale. In one instance,
stromatolites form a continuous layer of laminated, low-domal mounds.
Laminae thicken toward the crests of mounds (Fig. 4G), a key indicator
of microbial origin (Riding 1999), and these are interpreted as in situ
stromatolite mounds under Riding’s (1999) definition. They are the
‘‘laterally linked hemispheroids’’ type of Logan et al. (1964), which in the
modern of Shark Bay, Australia, form in protected, low-energy, intertidal
settings. A similar environment is inferred for in situ stromatolites at
Winfield Quarry.
This facies contains a low-diversity assemblage of unabraded fossils,
chiefly eurypterids, gastropods, and ostracods. This suite of sedimentary
structures indicates deposition in an environment that was above fair-
weather wave base (symmetrical ripple laminae), within the photic zone
(stromatolites and cryptalgal laminae), within the tidal range (heterolithic
bedding), with intermittent subaerial exposure (mudcracks) and more
extended periods of exposure in the supratidal zone (evaporites). Not all
sedimentary features are present in all instances of this facies, and specific
depositional environments are interpreted for units on a case-by-case basis
(refer to Inferred Depositional Setting and Relative Sea-Level Fluctuations
section).
Biomicrite to Biosparite Facies (F2a).—The biomicrite to biosparite
facies is characterized by the presence of megascopic fossils or fossil
fragments in a micrite matrix (Fig. 4H, 4I). Fossils are open-marine fauna
consisting of gastropods, brachiopods, bivalves, bryozoans, rugose corals,
crinoids, and sparse ostracods. In many instances, fossils are concentrated
in pods likely formed by bioturbation or winnowing of fines. In some
instances, weathered surfaces appear mottled (Fig. 4H), also possibly
resulting from bioturbation. The varying degrees of abrasion and
orientation of fossils indicate deposition in open marine settings from
subtidal but above fair-weather wave base, for beds with highly abraded
fossils, to lower energy environments between fair-weather and storm wave
base, for beds with abundant unabraded fossils. Some instances contain
symmetrical ripples (Fig. 4J), indicating deposition above fair-weather
wave base.
Some beds contain cm-scale fining-upwards successions, which form
under waning-flow conditions, and could be interpreted as either tidal
channels near to where the fossils were abraded or as turbidity flows
formed below normal wave base and distal to the environment in which the
fossils were abraded. From the association of these beds with relatively
shallow facies and their lack of definitive deep-water indicators, they are
interpreted as tidal-channel deposits (refer to Inferred Depositional Setting
and Relative Sea-Level Fluctuations for more details).
Sponge-Coral-Crinoid Biomicrite to Biosparite Facies (F2b).—The
sponge-coral-crinoid biomicrite to biosparite facies is characterized by the
presence of sponges (stromatoporoids) and(or) corals (Fig. 4K, 4L).
Stromatoporoids are discontinuous, overturned, and abraded, in some
places including oncolites with concentric growth strata (Fig. 4L). These
deposits also contain tabulate and rugose coral, crinoids, and highly
abraded, unidentifiable fossil fragments. These are interpreted as reef-
flank deposits formed in an environment with sufficient wave energy to
rotate oncoids and abrade fossils, above fair-weather wave base and
within the photic zone. Some intervals contain shale partings, which may
indicate slack water suspension fallout associated with tides or lulls in
wave energy. While no framework reefs are present in Winfield Quarry
strata, they have been documented in correlative strata (e.g., Cole et al.
2015).
Sandy Intrabiosparite Facies (F3).—The sandy intrabiosparite facies
consists of coarse-sand- to granule-size quartz and calcareous clasts with
sparse disarticulated brachiopods and crinoid ossicles (Fig. 5A). The lack
of finer grained sediments indicates that wave energy was sufficient to
winnow away mud-sized particles from the depositional environment. This
facies is interpreted as having been deposited in an open marine, above
fair-weather wave base environment.
Shale with Fossils and Ichnofabrics Facies (F4a).—The shale with
fossils and ichnofabrics facies is a medium to dark gray shale and
SEDIMENTOLOGY AND ISOTOPE STRATIGRAPHY OF SILURIAN–DEVONIAN STRATAP A L A I O S 409
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Zoophyc
os
(in
som
eunit
spre
val
ent)
none
shal
epar
tings
to
inte
rbed
ded
shal
es
inte
rtid
al–su
bti
dal
bel
ow
storm
wav
ebas
e;so
me
unit
soxygen
lim
ited
1b:
Mic
rite
wit
h
sedim
enta
ryst
ruct
ure
s
mic
rite
-arg
illa
ceous
mic
rite
finel
yla
min
ated
toth
ick
tabula
r,nodula
r,
or
lenti
cula
r
mudcr
acks,
evap
ori
tes,
het
eroli
thic
bed
din
g,
convolu
te,
ripple
or
crypta
lgal
lam
inae
,
intr
acla
sts,
spar
se
hum
mock
s,sp
arse
fenes
trae
none
spar
seost
raco
ds
wher
enot
lam
inat
ed,
spar
sefo
ssil
frag
men
ts,
bry
ozo
ans,
eury
pte
rids,
stro
mat
oli
tes
shal
epar
tings
to
inte
rbed
ded
shal
es
inte
rtid
al–su
pra
tidal
2a:
Bio
mic
rite
to
bio
spar
ite
(spar
se)(
intr
a)bio
mic
rite
to(i
ntr
a)bio
spar
ite
or
pac
ked
(intr
a)
bio
mic
rite
,non-
to
ver
yar
gil
lace
ous
thin
toth
ick
tabula
rto
nodula
rpods
and
dis
conti
nuous
ban
ds
of
mic
rite
,ra
reev
apori
tes,
spar
sem
icri
tein
trac
last
s,
lam
inae
,sy
mm
etri
cal
wav
e
ripple
s,or
hum
mock
y
cross
-str
atif
icat
ion
and
finin
g-u
pw
ards
sequen
ces;
cher
tnodule
sab
undan
tin
som
ela
yer
s
spar
seC
hondri
tes;
mott
ling
and
conce
ntr
atio
nof
foss
ils
inpods
poss
ibly
resu
ltin
gfr
om
bio
turb
atio
n
spar
se–pac
ked
,hig
hly
abra
ded
–unab
raded
gas
tropods,
bra
chio
pods,
biv
alves
,ost
raco
des
,
bry
ozo
ans,
rugose
cora
ls,
crin
oid
sc
spar
sesh
ale
par
tings
toin
terb
edded
thin
shal
es
subti
dal
,dom
inan
tly
abov
e
fair
-wea
ther
wav
ebas
e
2b:
Sponge-
cora
l-cr
inoid
bio
mic
rite
tobio
spar
ite
(intr
a)bio
mic
rite
to
bio
spar
ite
med
ium
nodula
rto
stro
mat
oli
tic
onco
lite
san
dso
ft-s
edim
ent
def
orm
atio
nin
som
eunit
s,
thro
mboli
tes
none
stro
mat
oporo
ids,
tabula
te
and
rugose
cora
ls,
crin
oid
s,sp
arse
ost
raco
des
,unid
enti
fiab
le
foss
ilfr
agm
ents
none
tosh
ale
par
tings
toth
insh
ales
subti
dal
above
fair
-wea
ther
wav
ebas
e,w
ithin
the
photi
czo
ne
3:
San
dy
intr
abio
spar
ite
coar
se-s
and
togra
nule
sandy
intr
abio
spar
ite
thic
km
assi
ve
centi
met
er-s
cale
finin
g
upw
ards
sequen
ces
none
spar
sedis
arti
cula
ted
bra
chio
pods,
crin
oid
s
none
subti
dal
above
fair
-wea
ther
wav
ebas
e
4a:
Shal
ew
ith
foss
ils
and
ichnofa
bri
cs
dar
kgra
ysh
ale
and
calc
areo
us
silt
stone
thin
tabula
ran
dfi
ssil
egen
eral
lynone,
one
2-c
m
thic
kla
yer
wit
hch
ert
nodule
s
Chondri
tes,
nondes
crip
t
ichnofa
bri
cs
ost
raco
des
,sp
arse
moll
usk
s
and
bra
chio
podsd
N/A
low
ener
gy,
subti
dal
bel
ow
storm
wav
ebas
e,
oxygen
lim
ited
4b:
Bar
ren
shal
ebla
cksh
ale
thin
tabula
ran
dfi
ssil
enone
none
abundan
tli
nguli
d
bra
chio
pods
inone
inte
rval
N/A
low
ener
gy,
subti
dal
bel
ow
fair
-wea
ther
wav
ebas
e,
oxygen
lim
ited
aD
r.T
ony
Ekdal
eid
enti
fied
man
ytr
ace
foss
ils.
bD
r.C
arl
Bre
ttid
enti
fied
man
ym
egaf
oss
ils.
cId
enti
fiab
lefo
ssil
sin
clude
Dis
com
yort
his
,A
crosp
irif
ercf
.m
urc
his
oni,
Sch
uch
erte
lla
cf.
bra
chyp
rion
,C
ost
elli
rost
rata
pec
uli
ari
s,L
epto
coel
iaflabel
lite
s,poss
ibly
Mer
iste
lla
laev
is,
Pen
tam
erus
cf.
gyp
idula
,an
d
‘‘S
chuch
etel
la’’
woolw
ort
hia
na.
dId
enti
fiab
lefo
ssil
sin
clude
Coel
osp
ira
dic
hto
ma
,A
ctin
opte
ria
cf.
com
munis
,D
ale
gin
aobla
ta,
Coel
osp
ira
,an
dposs
ibly
asm
all,
nar
row
rhynch
onel
lid
(Ste
norh
ynch
us)
,C
honost
rophie
lla
,L
epta
ena
rhom
boid
ali
s,
Orb
iculo
idea
cf.
dis
ca,
Tye
rsel
laper
eleg
ans,
and
Dis
com
yort
his
.
A.V. Hess and J.M. Trop410 P A L A I O S
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siltstone with fossils, including ostracods and very sparse mollusks and
brachiopods, and in many instances intense Chondrites bioturbation (Fig.
5B, lower three-quarters of Fig. 5C). Fossils include Orbiculoidea and
nuculid bivalves, which can indicate an oxygen-limited environment
(Brett et al. 1991). The Chondrites ichnofacies is also common in
oxygen-limited areas, even exceeding Zoophycos in the degree of dysoxia
it can tolerate (Bromley and Ekdale 1984). This facies therefore
represents deposition in an environment below storm wave base in
oxygen-limited waters (Fig. 6).
Barren Shale Facies (F4b).—The barren shale facies is characterized
by dark gray to black shale lacking macrofossils and biogenic and
FIG. 4.—Photographs of key features of facies F1 and F2 used in identifying depositional environments, in order of facies listed in table 1. A) Zoophycos mottling on
bedding-plane surface of block, Shriver Member of Old Port Formation F1a. B) Close-up view of bedding-plane surface showing arcing Zoophycos traces (arcs indicated by
white arrows), same interval as Figure 4A. C) Mudcracks (m) on bedding plane surface and horizon of evaporites (e) on cross-section view, Tonoloway Formation F1b. D)
Evaporite vugs (e) and laminations, Tonoloway Formation F1b. E) Stromatolite bed, Tonoloway Formation F1b. F) Heterolithic bedding (h) and scours (s), La Vale Member of
Keyser Formation F1b.
SEDIMENTOLOGY AND ISOTOPE STRATIGRAPHY OF SILURIAN–DEVONIAN STRATAP A L A I O S 411
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sedimentary structures (upper quarter of Fig. 5C). The dark color of this
facies is likely due to high concentrations of organic material, and it
may therefore represent oxygen-limited conditions that would have
precluded the presence of bacteria able to break down this organic
matter. The lack of fossils and biogenic structures supports this
interpretation (Bromley and Ekdale 1984), and this facies is interpreted
to represent the most oxygen-deprived environment preserved in the
WQ1 section (Fig. 6). The lack of sedimentary structures indicates
deposition in a low-energy environment. While these conditions can
occur in both lagoonal and offshore settings well below the influence of
fair-weather and storm wave base, regional correlation of the Mandata
Member, in which a large part of the facies occurs, indicates that it is a
deep-water equivalent of sands being shed from the mountains to the
east (Smosna 1988).
FIG. 4.—Continued. Photographs of key features of facies F1 and F2 used in identifying depositional environments, in order of facies listed in table 1. G) In situ
stromatolite mounds, New Creek-Corriganville Members of Old Port Formation F1b. H) Gray and tan mottling, possibly from bioturbation, Keyser Formation F2a. I)
Crinoidal biomicrite, Keyser Formation F2a. J) Symmetrical wave ripples, Byers Island Member of Keyser Formation F2a. K) Tabulate coral (t) and crinoids (c), Keyser
Formation F2b. L) Stromatoporoids, likely not in growth position, La Vale Member of Keyser Formation F2b.
A.V. Hess and J.M. Trop412 P A L A I O S
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Instances of this facies outside of the Mandata Member are thin (,2 m)
and are associated with shallower-water facies. One contains abundant
lingulid brachiopods, which are associated with nearshore dysaerobic
environments (Kammer et al. 1986), and the low-diversity, high-abundance
assemblage indicates a stressed environment, perhaps due to changes in
oxygenation or salinity. These units are interpreted as representing
dysaerobic, below-fair-weather wave base environments, shallower water
than for the bulk of this facies.
FIG. 5.—Photographs of key features of facies F3, F4, and F5 used in identifying depositional environments, in order of facies listed in Table 1. A) Coarse sand- to granule-
size quartz clasts and abraded brachiopod fragments (bf), New Creek-Corriganville Members of Old Port Formation F3. B) Chondrites burrows on bedding-plane surface,
Mandata Member of Old Port Formation F4a. C) Compacted Chondrites burrows (c) and brachiopod fragments (bf) of facies F4a, overlain by dark, barren shale of facies F4b
at top quarter of frame, Mandata Member of Old Port Formation. D) Bentonite (altered volcanic ash) (orange), Mandata Member of Old Port Formation.
FIG. 6.—Summary of features observed in the studied stratigraphy and corresponding interpretations of bottom-water oxygenation during deposition. See Table 1 for
description of facies.
SEDIMENTOLOGY AND ISOTOPE STRATIGRAPHY OF SILURIAN–DEVONIAN STRATAP A L A I O S 413
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Possible Volcanic Ash.—In addition to the sedimentary facies, eight
beds of what may be bentonites (altered volcanic ash) are also preserved in
WQ1. They are thin (,10-cm thick), clay-rich (sticky when wetted), and
weather bright orange, often leaching color to underlying beds (Fig. 5D).
The thickest horizon, in the Mandata, was sampled and yielded doubly
terminated euhedral zircons (see Online Supplemental File) indicative of
airfall ash.
Inferred Depositional Setting and Relative Sea-Level Fluctuations
This section summarizes the stratigraphic distribution of the facies
documented in the previous section (Fig. 7) and relative sea-level
fluctuations inferred from the upsection facies changes (Fig. 8A–8C).
Tonoloway Formation.—The base of WQl consists of ~7 m of
Tonoloway Formation laminated micrite (F1b; Fig. 7). Laminae show the
FIG. 7.—Stratigraphic section WQ1 from Winfield Quarry, PA. Abbreviations: Fm. ¼ Formation; Mbr.¼Member.
A.V. Hess and J.M. Trop414 P A L A I O S
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FIG. 8.—Stratigraphy, relative sea level, transgressive-regressive cycles, and geochemistry for section WQ1, Winfield, PA, and equivalent strata south of Pennsylvania and
in New York based on lithologic correlation (Fig. 3). A) Generalized stratigraphy for section WQ1. Silurian–Devonian boundary age is from Cohen et al. (2008); boundary is
SEDIMENTOLOGY AND ISOTOPE STRATIGRAPHY OF SILURIAN–DEVONIAN STRATAP A L A I O S 415
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convex geometry of cryptalgal laminae and stromatolites, evaporites, and
mudcracks are also abundant. Laminae are lacking in some portions of this
stratigraphic package. Identifiable fossils are for the most part limited to
sparse ostracods, with unidentifiable fossil fragments also present. These
strata are interpreted to represent deposition in shallow-water intertidal to
supratidal environments, including carbonate tidal flats (Fig. 8B).
An exposure ~580 m along strike from the base of section WQ1 along
the north wall of Winfield Quarry contains an exceptionally well-preserved
eurypterid Lagerstatte ~2 m below the top of the Tonoloway Formation
(Vrazo et al. 2014). The exceptional exposure in the quarry allowed for
physical tracing of this bed to the WQ1 section. Upon close inspection, two
partial eurypterid fossils of the taxa noted by Vrazo et al. (2014;
Eurypterus cf. remipes) were found in the Tonoloway Formation of WQ1
and it is likely that the 3.2-m-thick covered section 2 m below the contact
between the Tonoloway and Keyser Formations correlates to the Lager-
statte exposed along strike within Winfield Quarry.
In the uppermost 1.5 m of the Tonoloway Formation, sedimentary
structures are lacking and the concentration of evaporites gradually
decreases. The boundary between the Tonoloway and the Byers Island
Member of the Keyser Formation is marked by an increase in fossil
abundance and diversity from sparse ostracods in the Tonoloway to
bryozoans, brachiopods, bivalves, gastropods, ostracods, and rugose
corals typical of F2a in the Keyser. This transition is gradational from 5.9
to 7.6 m and the formation boundary is picked at 7.6 m in WQ1, the point
where the rate of increase in fossil abundance slows. The loss of
evaporites and mudcracks and the increasing fossil abundance and
diversity indicate freshening and minor relative sea-level rise across the
contact between the Tonoloway and Keyser Formations.
Keyser Formation Byers Island Member.—The Byers Island
Member is distinguished by the nodularity of its beds (Head 1969). It is
biomicrite (F2a) with normal marine fauna and is interpreted to represent
deepening to a subtidal above fair-weather wave base environment. The
upper contact of this member is chosen at 12.8 m, where consistently
nodular strata become more sporadically nodular.
Keyser Formation Jersey Shore Member.—Fossils in the nodular
biomicrite (F2a) of the Jersey Shore Member are fragmented and randomly
oriented. They become less prevalent upsection to about 23 m and are lost
entirely from 13 to 15 m where there is a package of massive micrite (F1a).
Two stromatoporoid-bearing units (F2b) are at 17–18 m and 26–31 m, and
the lower contains oncoids while the upper contains fragmented fossils that
become increasingly abundant and diverse upsection. The covered section
at 23–26 m is exposed in nearby parts of the quarry, where it contains
stromatoporoids, Favosites corals, and abundant crinoid ossicles; it is
inferred to also be facies F2b. The presence of oncoids and stromatop-
oroids indicate that these formed in a high-energy environment within the
photic zone during continued relative sea-level rise. As the corals and
stromatoporoids are mainly not in life position, these units are interpreted
as reef-margin deposits that would have formed adjacent to reefs. Above
the covered section in WQ1, stromatoporoids are present up to 31 m and
other fossils are fragmented and increasingly abundant and diverse. The
top of the stromatoporoid-bearing strata at 31 m was chosen as the
boundary between the Jersey Shore and overlying La Vale Member.
Keyser Formation La Vale Member.—The La Vale Member is
biomicrite, biosparite, and argillacous biomicrite (F2a). A return to non-
reef margin biomicrites stratigraphically above the reef margin unit may
indicate a relative sea-level fall and a return to environments similar to
those inferred from strata below the reef-margin package. Alternatively, sea
level may have continued to rise, as depositional environments would have
been broadly similar both landward and seaward of the reef. Starting at
~45 m, fossils are gradually more abraded upsection and cm-scale fining-
upwards successions are noted at ~50 m. Based on the stratigraphic
context and lack of definitive deep-water features, they are interpreted as
having formed by waning flow in tidal channels and bars, indicating that by
this point relative sea level had begun to fall. Upsection, strata grade into
laminated micrite (F1b), argillaceous micrite (F1a), and finally a package
of micrite and interbedded shales from ~61 to 64 m in which the micrites
exhibit mudcracks, cm-scale cut-and-fill structures, sparse fenestrae, and
heterolithic bedding with silt-sized particles showing ripple-scale multidi-
rectional planar crossbedding (F1b). The variations observed in the La Vale
Member are consistent with tidally influenced nearshore environments and
indicate an overall regressive trend culminating with interbedded micrites
and shales at the top of the unit deposited in an intertidal environment
frequently subject to subaerial exposure and tidal influence.
Old Port Formation New Creek and Corriganville Members.—A
distinct contact separates the Keyser and Old Port Formations at 64 m
above the base of the section. Interbedded micrites and shales of the
uppermost Keyser Formation occur below ~l m of in situ mounded
stromatolites (F1b) of the New Creek-Corriganville Members of the Old
Port Formation. It is an apparently conformable contact with shallow
marine facies above and below and no evidence of erosion or prolonged
exposure. In situ stromatolites are interpreted to have formed in a protected
intertidal environment.
Above the in situ stromatolites is a ~1-m-thick cross-bedded, sandy
intrabiosparite (F3) representing siliciclastic input into the basin and
similar to that described by Inners (1981) ~1 m above the contact in the
Bloomsburg and Mifflinville Quadrangles ~15 km to the east. The sandy
unit is overlain by a series of biosparite, micrite, and biomicrite strata with
moderate to sparse, dominantly abraded fossils, which indicate a deepening
to a shallow subtidal environment above fair-weather wave base.
Old Port Formation Mandata Member.—An abrupt transition to
shale and siltstone at ~71 m marks the contact between the New Creek-
Corriganville and Mandata Members. Packages of dark gray bioturbated
shale with sparse fossils (F4a) and black, barren shale (F4b) are punctuated
by tens-of-centimeter-thick beds of nodular micrite and biomicrite.
Together, these facies indicate deposition in a subtidal environment below
storm wave base following a rapid relative sea-level rise at the base of the
Mandata Member. Black shales are interpreted to represent times when
bottom waters were the most inhospitable to normal marine fauna, oxygen
limited, and conducive to preservation of organic material. Micrite,
biomicrite, and fossiliferous shale with Chondrites bioturbation are
interpreted to represent times of oxygen limitation, but to a lesser degree
than during deposition of facies F4a (Fig. 6). Precipitated pyrite is common
throughout this member, further supporting the interpretation of oxygen-
limited, likely euxinic conditions. At a time when global atmospheric and
approximate. See Figure 7 for explanation of symbols. B) Interpreted relative sea-level curve for section WQ1. Gray shading indicates interpreted oxygen limitation during
deposition, with darker shading indicating increasing oxygen limitation. C) Transgressive-regressive cycles from section WQ1 (black), south of Pennsylvania (blue, from
Dorobek and Read 1986), and New York (red, from Laporte 1969 and Belak 1980). D) Isotope data from section WQ1 (black) and West Virginia (light blue and dark blue,
Saltzman 2002 and Husson et al. 2016, respectively) plotted relative to stratigraphic position. Red box indicates peak carbon isotope values in New York (Husson et al. 2016).
Abbreviations: Fm.¼ Formation; Mbr.¼Member, FWWB¼ fair-weather wave base; SWB¼ storm wave base; VA¼Virginia; WV¼West Virginia; MD¼Maryland; PA¼Pennsylvania; NY ¼ New York.
A.V. Hess and J.M. Trop416 P A L A I O S
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surface-water oxygen levels were rising (Lenton et al. 2016; Lu et al.
2018), there is evidence for oxygen limitation in the Appalachian Basin.
The change from relative sea-level rise to fall is placed at ~75 m, where a
minor increase in oxygenation is inferred from the change in facies from
mainly F4b to F4a.
Old Port Formation Shriver Member.—Above the Mandata Member
is an abrupt transition to the Shriver Member, which consists of micrite
with interbedded shales (F1a). Zoophycos feeding traces are prevalent on
some bedding planes from ~81 to 87 m. Due to the nature of exposure in
the quarry it is difficult to directly observe bedding planes in intervals
higher than ~87 m, though it appears that Zoophycos permeates the
majority of this unit. The lack of fossils and presence of Zoophycos
indicate continued deposition under oxygen-limited subtidal below storm
wave base conditions, though under slightly more oxygenated conditions
than for underlying deposits (Fig. 6); such conditions would have
prevented the preservation of as much organic matter as observed in the
Mandata Member black shales. As with the underlying Mandata Member,
precipitated pyrite is common in this part of the section, providing further
support for continued oxygen limitation and likely euxinia.
Old Port Formation Ridgeley Member.—The boundary between the
Shriver and Ridgeley Members is marked by an abrupt increase in fossil
content. From ~99 to 106 m, the Ridgeley Member is biomicrite (F2a) in
which fossils are less fragmented than in the Keyser Formation.
Argillaceous biomicrite makes up the remainder of the section from
~106 to 113 m, and the fossils in this unit are dominantly unabraded
gastropods and robust, abraded to unabraded brachiopods. The presence of
fossils indicates the return of normal-marine, subtidal below fair-weather
wave base conditions, likely the result of continued relative sea-level fall.
The top of the Winfield Quarry outcrop is in the Ridgeley Member and the
top of the Old Port Formation is not preserved.
Possible Volcanic Ash Beds.—Seven of the possible volcanic ash beds
occur in the Keyser Formation, one in the Jersey Shore Member at 15.3 m
and six in the La Vale Member at 38.3, 41.1, 43.6, 47.3, 51.1, and 53.5 m.
No works have thus far documented volcanic ashes in the Keyser
Formation. If these are in fact volcanic ashes, they may be the oldest in the
Devonian of the Appalachian Basin and the earliest indication of the
beginning of the Acadian orogeny. Alternatively, it is possible that the clay-
rich layers recorded here are detrital terrestrial clays. The uppermost bed
occurs in the Mandata at 73.5 m; it is this bed that yielded doubly
terminated euhedral zircons (see Online Supplemental File) and is
therefore considered a confirmed bentonite.
GEOCHEMISTRY
Micrite samples from this stratigraphic section show an 8.7% increase
in d13Ccarb from the base of the section to the upper part of the La Vale
Member of the Keyser Formation (Fig. 8D, Table 2). Values rise from a
minimum of -4.3% in the Tonoloway to a high ofþ4.4% in the upper La
Vale. A gap in the data through most of the Jersey Shore and the lower part
of the La Vale reflects the high fossil content through this part of the
section, as only samples devoid of visible biotic and sparry components
were sampled. Carbon isotope values then decrease by .5% to a low in
the Mandata Member of the Old Port Formation.
Oxygen isotope (d18Ocarb) values range from -7.3 to -4.1%. From the
base of the section in the Tonoloway Formation to the base of the data gap
that begins in the Jersey Shore Member of the Keyser Formation, values
increase overall from -7.3 to -6.1%. From the middle of the La Vale Member
of the Keyser to midway through the New Creek-Corriganville Members
(~66 m), values vary between -6.9 and -5.2%. Above this to the top of the
sampled interval in the Shriver Member of the Old Port Formation, values
are overall ~1% higher, varying between -6.4 and -4.1%.
Comparison of the oxygen and carbon isotope compositions permits
evaluation of diagenetic overprinting. A plot of carbon versus oxygen
isotope values for the entire stratigraphic column (Fig. 9) shows little
correlation (R2¼0.01). Most individual facies also show little correlation
(R2,0.15). Isotope values for facies F1b show some correlation (R2¼0.39),
but this can be partially explained by two populations of points created by
two different stratigraphic occurrences of this facies. Relatively low isotope
values are recorded in the Tonoloway Formation and lower part of the
Keyser Formation; relatively high isotope values are recorded in the lower
part of the Old Port Formation and upper part of the Keyser Formation.
When trendlines for those intervals are plotted separately, the correlation in
the lower part of the section disappears (R2¼0.00) and that in the upper part
of the section is substantially reduced (R2¼0.29). Thus, the lack of
correlation between carbon and oxygen isotope values suggests that the
FIG. 9.—Carbon versus oxygen isotope values with trendlines and R2 values for all data and for each facies. Symbol color and shape by facies. Trendline for facies F2a
excluded due to insufficient data. Refer to Table 1 for facies information.
SEDIMENTOLOGY AND ISOTOPE STRATIGRAPHY OF SILURIAN–DEVONIAN STRATAP A L A I O S 417
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sampled micrite matrix generally provides a faithful record of primary
seawater d13C values.
However, a few anomalously low carbon isotope values in the organic-
rich Mandata Member of the Old Port Formation may record early
diagenetic cementation. Two carbon isotope values (at 72.24 and 74.49 m
above the base of the section) are anomalously low compared to samples
from adjacent strata. It is possible that remineralization of organic matter in
the sampled shale resulted in an isotopically light early cement (e.g.,
Weissert et al. 2008). However, carbon isotope values decrease from the
peak of the positive carbon isotope excursion beginning ~8 m strati-
graphically below the Mandata Member, so the stratigraphic position of the
positive excursion is well constrained.
Another possible concern is alteration of the isotopic signature by
meteoric diagenesis, especially for very shallow-water facies (e.g., at the
boundary between the Keyser and Old Port Formations). However, the
occurrence and similar magnitude of the positive excursion throughout the
Appalachian Basin suggests that any effect is minimal. Finally, restriction
in shallow-marine environments can cause the carbon isotope values of the
dissolved inorganic carbon in those environments to be lower than those in
the open ocean, typically resulting in positive carbon isotope excursions in
deep-water facies or during rapid transgression (e.g., Patterson and Walter
1994; Immenhauser et al. 2003; Saltzman and Edwards 2017). This is
opposite of the pattern observed here, with the positive carbon isotope
excursion recorded in the shallowest-water facies. Nevertheless, caution
should be used when comparing the absolute values of the record presented
here with data from distant locations.
DISCUSSION
Parts of three transgression-regression cycles have been identified in
Winfield Quarry strata (Fig. 8B, 8C). The first is the final portion of a
regressive phase in the Tonoloway Formation. The second is a
transgression through the Byers Island and Jersey Shore Members of the
Keyser Formation and a regression through the La Vale Member. The third
TABLE 2.—d13Ccarb and d18Ocarb values for stratigraphic section WQ1 micrite samples.
Stratigraphic level
(meters above
base of section) d13C
d13C Analysis
standard
deviation d18O
d18O Analysis
standard
deviation
Stratigraphic level
(meters above
base of section) d13C
d13C Analysis
standard
deviation d18O
d18O Analysis
standard
deviation
0.81 -1.7 0.07 -7.3 0.07 63.05 2.6 0.02 -6.3 0.08
2.48 -4.3 0.04 -7.3 0.07 63.37 3.1 0.05 -6.9 0.03
3.10 -4.0 0.05 -7.0 0.03 63.44 1.6 0.03 -6.8 0.06
6.05 -3.0 0.03 -6.4 0.03 65.97 0.7 0.09 -6.9 0.09
6.31 -2.9 0.03 -6.8 0.04 65.97 0.8 0.03 -6.1 0.05
10.71 -2.5 0.03 -6.4 0.05 66.64 1.4 0.06 -5.3 0.09
10.79 -2.9 0.06 -6.3 0.07 66.64 1.4 0.05 -5.8 0.09
10.84 -2.7 0.03 -6.6 0.07 66.81 1.5 0.04 -5.0 0.08
12.86 -0.9 0.02 -6.3 0.08 67.05 1.5 0.02 -5.2 0.06
13.17 -0.9 0.05 -6.3 0.06 67.30 1.5 0.04 -5.2 0.08
13.17 -0.9 0.06 -6.2 0.09 67.30 1.3 0.05 -5.6 0.06
13.31 -1.0 0.04 -6.2 0.06 67.76 1.0 0.03 -5.0 0.03
18.97 -0.5 0.04 -6.1 0.04 67.86 1.5 0.04 -5.5 0.04
44.67 2.7 0.05 -6.3 0.06 68.85 0.5 0.04 -4.7 0.06
44.84 2.2 0.03 -5.9 0.08 68.85 0.4 0.04 -4.3 0.08
45.13 1.4 0.06 -5.2 0.15 68.85 0.4 0.06 -4.4 0.06
47.42 3.4 0.03 -5.8 0.10 71.90 0.6 0.03 -4.8 0.10
47.42 3.3 0.04 -6.3 0.04 71.90 0.6 0.05 -3.9 0.09
48.85 3.4 0.03 -6.1 0.07 71.90 0.7 0.05 -4.9 0.06
48.85 3.3 0.05 -6.3 0.04 72.24 -1.1 0.06 -5.9 0.08
49.81 2.7 0.04 -6.0 0.07 72.24 -1.1 0.06 -5.5 0.06
49.96 2.9 0.03 -6.2 0.06 72.75 0.1 0.05 -5.5 0.04
50.00 3.6 0.05 -5.2 0.05 72.75 0.1 0.06 -5.3 0.10
51.28 2.5 0.05 -5.7 0.05 72.75 0.2 0.06 -5.3 0.06
51.85 2.2 0.06 -5.9 0.07 73.00 0.0 0.03 -7.1 0.09
52.30 2.2 0.05 -6.1 0.08 73.00 -0.2 0.03 -5.3 0.06
52.30 2.1 0.06 -6.0 0.07 73.38 0.4 0.06 -4.9 0.05
54.36 3.2 0.03 -6.9 0.07 73.92 -0.4 0.06 -5.5 0.06
57.91 3.7 0.03 -5.8 0.06 74.19 -0.7 0.05 -4.5 0.09
58.61 3.6 0.05 -5.9 0.07 74.19 -0.7 0.07 -4.2 0.07
59.00 3.6 0.02 -5.7 0.08 74.19 -0.7 0.05 -4.9 0.07
59.41 3.1 0.03 -5.1 0.06 74.49 -4.4 0.02 -4.9 0.07
59.90 3.1 0.04 -5.4 0.04 74.49 -4.0 0.06 -4.0 0.08
59.90 3.2 0.06 -5.3 0.06 75.53 -0.6 0.04 -4.1 0.09
60.90 2.9 0.06 -5.6 0.08 76.30 0.0 0.06 -6.1 0.08
60.90 2.8 0.03 -5.7 0.04 78.10 0.6 0.05 -4.9 0.10
61.86 4.4 0.05 -6.0 0.07 80.24 0.9 0.06 -5.4 0.11
62.00 4.4 0.05 -6.3 0.06 80.92 1.2 0.04 -4.9 0.05
62.00 4.4 0.04 -6.2 0.10 81.30 0.9 0.03 -4.5 0.06
62.37 3.6 0.04 -6.7 0.08 82.01 1.1 0.06 -6.4 0.13
62.49 2.7 0.05 -6.3 0.07 83.88 1.6 0.06 -5.0 0.13
62.82 2.9 0.06 -6.9 0.09 87.96 1.8 0.06 -4.8 0.06
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includes a transgression through the New Creek-Corriganville Members of
the Old Port Formation and part of the Mandata Member and a regression
through the remainder of the Mandata, Shriver, and Ridgeley Members.
Transgressive-regressive cycles interpreted elsewhere in the basin by
other researchers were added to Figure 8C using correlation based on
lithology (Formation and Member equivalencies; Fig. 3). They do not, for
the most part, coincide with cycles documented here. One exception is the
cycle interpreted for Keyser-equivalent strata in New York, though this
correlation, with no intervening outcrop, is uncertain. The relative
lowstand at the top of the Keyser Formation also roughly coincides with
that in the New Creek of the southern outcrop belt, as noted by Saltzman
(2002). The overall misalignment of transgressive-regressive cycles across
the basin could result from lateral facies changes affecting lithologic
correlations, differential tectonic activity affecting accommodation and
clastic sediment supply, or both.
The positive carbon isotope excursion at the Silurian–Devonian
boundary is a global event and should peak at the same time in strata
throughout the Appalachian Basin. The stratigraphic peak of the excursion
can therefore be used to test whether the lithologic correlations shown in
Figure 3 in fact correlate time-equivalent strata; if they do, lithologic
correlation of sections with carbon isotope data should show coincident
isotope trends, including the stratigraphic placement of the positive
excursion at the Silurian–Devonian boundary. This idea was originally put
forth by Husson et al. (2016), who used 206Pb/238U dating of volcanic
ashes to show that carbon isotope stratigraphy can result in a viable
correlation of the Silurian–Devonian boundary interval across the
Appalachian Basin.
The excursion was first documented in the Appalachian Basin by
Saltzman (2002) at Smoke Hole, West Virginia (Fig. 1), where it peaks at
~5% in the upper Keyser Formation. Husson et al. (2016) resampled that
section at higher resolution, confirmed Saltzman’s (2002) trend, and
additionally documented the excursion at four sections in New York where
it peaks at ~3.5% in the upper Manlius Formation, ~5.3% in the lower
Coeymans Formation, and ~3.5% in the lower Kalkberg Formation. To
test whether lithology-based correlations (Fig. 3) represent timelines, their
carbon isotope data from West Virginia was pinned at stratigraphic unit
boundaries and stretched and squeezed uniformly between those
boundaries (Fig. 8D). This correlation places the West Virginia excursion
about 14 m stratigraphically below its peak in Winfield Quarry (compare
blue and black d13C data in Fig. 8D). Uncertainty in the lithologic
correlation between the northern and southern outcrop belts prohibits
reliable correlation with the New York data at this level of detail, though
the excursion would peak higher in the section than at Winfield Quarry
(red bar in Fig. 8D). Husson et al. (2016) also noted that a facies-based
correlation results in an apparently diachronous carbon isotope excursion
across the basin. They concluded that it is in fact the formation and
member boundaries that are diachronous, as originally suggested by
Rickard (1962) and Laporte (1969), and therefore correlated instead using
carbon isotope stratigraphy.
The Winfield Quarry section has been added to Husson et al.’s (2016)
carbon-isotope-based correlation by stretching, squeezing, and cutting the
isotope curve and accompanying stratigraphic section relative to the
reference curve in New York (Fig. 10), under the assumption that changes
in d13C occurred at the same time throughout the Appalachian basin. The
correlation (Fig. 10A) indicates that the Keyser Formation at Winfield
Quarry is equivalent to the Keyser and Tonoloway Formations in West
Virginia and parts of the Rondout, Manlius, and Coeymans Formations in
New York. The New Creek-Corriganville Members at Winfield Quarry are
almost entirely equivalent to the New Creek Formation in West Virginia
and parts of the Kalkberg and New Scotland Formations in New York. The
Mandata Member is equivalent to at least part of the Corriganville
Formation in West Virginia and parts of the Kalkberg, New Scotland, and
Becraft Formations in New York.
Stretching and squeezing of the section during correlation has
implications for relative sedimentation rates between the WQ1 section
and the New York reference section. Stretching implies a lower
sedimentation rate, periods of nondeposition or erosion, or higher
compaction for the WQ1 section relative to the New York reference
section, and squeezing implies a higher sedimentation rate or lower
compaction. For the correlation to be viable, the relative sedimentation
rates implied by the stretching and squeezing factors for the WQ1 section
and the reference section in New York must make sense for their
depositional environments (e.g., lower sedimentation rates for shale than
for reefal carbonates is reasonable, whereas the reverse is not).
The correlation of the lower, biomicrite part of the La Vale Member of
the Keyser Formation required squeezing of the WQ1 section and implies a
higher sedimentation rate there than in the New York section. As this part
of the Keyser Formation contains significant skeletal material, it is
reasonable that its sedimentation rate would be higher than that of the
thinly bedded, microbialite, lagoonal limestones described by Husson et al.
(2016) for the Manlius Formation. Carbon isotope values in the Tonoloway
and lower Keyser Formations are more negative than those at the base of
the section reported by Husson et al. (2016), indicating that the values
likely correlate with a lower part of the section not sampled by Husson et
al. (2016). Lacking data to correlate to, we applied the squeezing factor
from the upper Keyser Formation to the data gap and the points from the
underlying units, which places these points stratigraphically below the
Husson et al. (2016) data. Correlation of the upper, micritic part of the La
Vale Member of the Keyser Formation required stretching of the WQ1
section relative to the deeper-water (Laporte 1969) Coeymans Formation of
New York. As this part of the section was deposited in very shallow water
depths, accommodation is expected to have been limited, leading to slow
sedimentation or even bypass and erosion (Pomar 2001), which would
result in a thinner package than the Coeymans.
A hiatus between the Keyser Formation and the New Creek-Corrigan-
ville Members of the Old Port Formation is necessitated by increasingly
negative isotope values in the New Creek-Corriganville. This is consistent
with the very shallow water depths and limited accommodation for the
underlying unit. The New Creek-Corriganville part of the section in WQ1
was not stretched or squeezed during correlation. The implied similar
depositional rates for this unit and the Coeymans Formation in New York
are consistent with their similar shallow-shelf depositional environments
interpreted herein and by Laporte (1969), respectively. Correlation of the
Mandata Member, an organic-rich shale, required stretching relative to the
New Scotland Formation open-marine carbonates and Becraft sandstones
in the reference section. This stretching is reasonable because, while shelfal
carbonates, sandstones, and organic-rich shales can have similar
sedimentation rates (e.g., Walker et al. 1983; Stein 1986), shales compact
more (Baldwin and Butler 1985). Data from the Shriver Member extend
above the part of the section sampled by Husson et al. (2016). In the
absence of data to correlate to, they were extended without stretching or
squeezing.
Note that the correlation presented (Fig. 10) is an interpretation based on
the observed carbon isotope trends and that there is some uncertainty
inherent in the methodology. Unconformities have been documented in
correlative strata, particularly in northern areas (e.g., Ebert and Matteson
2003) and may also complicate interpreted correlations. The Winfield
Quarry data extend above and below the available data from New York and
West Virginia, and correlations in these parts of the section would benefit
from additional regional data. The peak of the excursion, which occurs
approximately at the Silurian–Devonian boundary according to Husson et
al.’s (2016) preferred interpretation, is better constrained and appears to
correlate well.
Compared to lithostratigraphic correlation, this chemostratigraphic
correlation is more consistent with a conodont biostratigraphy event
observed by other researchers across the Appalachian Basin. The first
SEDIMENTOLOGY AND ISOTOPE STRATIGRAPHY OF SILURIAN–DEVONIAN STRATAP A L A I O S 419
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appearance datum (FAD) of I. woschmidti occurs within 2 m of the
Silurian–Devonian boundary and has been used globally to constrain the
location of that boundary (Denkler and Harris 1988). In the southern
outcrop belt of the Appalachian Basin, this FAD has been documented near
the top of the Keyser Formation and in the New Creek Formation (Helfrich
1978; Denkler and Harris 1988). In the northern outcrop belt, it has been
documented in the Manlius and Coeymans Formations (Denkler and Harris
1988; Milunich and Ebert 1993; Natel et al. 1996; Kleffner et al. 2009),
which lithologic correlation marks as equivalent to units overlying the
Keyser Formation in the southern outcrop belt (Fig. 3).
Similarly, ages from volcanic ashes are more consistent with the
chemostratigraphic correlation than with lithostratigraphic correlations. An
ash bed in the Corriganville of West Virginia has been dated as 417.22 Ma,
and a series of ashes in the uppermost Coeymans and Kalkberg in New
York have been dated as 418.42–417.56 Ma (Husson et al. 2016). While
lithostratigraphic correlation places the New York ashes equivalent to or
stratigraphically above the West Virginia ash, chemostratigraphic correla-
tion places these ashes in stratigraphic order consistent with their ages
(compare Figs. 3 and 10).
FIG. 10.—Correlation based on carbon isotope data. Data from this study is in black; New York (red) and West Virginia (blue) data from Husson et al. (2016), except where
otherwise specified. Symbols in legend apply to all colors. Vertical scale is normalized stratigraphic position given relative to Husson et al.’s (2016) section H4a, b.
A) Stratigraphic sections (lithology) and transgressive-regressive cycles. Lithologies for stratigraphic section WQ1 converted to classification scheme used by Husson et al.
(2016) to facilitate combination of these data sets. B) Carbon isotope values on which this correlation is based. Gray shading indicates interpreted oxygen limitation during
deposition, with darker shading indicating increasing oxygen limitation. Silurian–Devonian boundary and age data from Husson et al. (2016). FAD I.w.w. is first appearance
datum of Icriodus woschmidti woschmidti. LAD O.e.d. is last occurrence datum of Oulodus elegans detorta. C) Factors by which data in this figure was vertically stretched or
squeezed expressed as 1 divided by the stretching or squeezing factor. H1 through H5 refer to Husson et al. (2016) stratigraphic section names. Abbreviations: WV¼West
Virginia; PA ¼ Pennsylvania; NY ¼ New York; To ¼ Tonoloway; Corr ¼ Corriganville; NC-C ¼ New Creek-Corriganville; Sh ¼ Shriver; Ro ¼ Rondout; Co¼ Coeymans.
A.V. Hess and J.M. Trop420 P A L A I O S
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The transgressive-regressive cycles documented herein record local
change in relative sea level from as shallow as supratidal environments to
as deep as below storm wave base. Dorobek and Read (1986) estimated the
water depth of storm wave base at this time in the Appalachian Basin as
50–60 m or deeper, on the basis of thicknesses of sedimentary packages
from which they approximated the slope of the Appalachian Basin ramp
(10–15 cm/km). Haq and Schutter (2008) show a maximum of ~80 m of
global sea-level change for third-order fluctuations through the latest
Silurian and earliest Devonian (Pridolian and Lochkovian). Therefore,
from the local record of relative sea-level change alone, it is possible that
the transgressive-regressive cycles at WQ1 are the result of eustatic sea-
level change. However, if eustasy was the primary driver, relative sea-level
cycles would be coincident throughout the Appalachian Basin, and the
chemostratigraphic correlation does not support this scenario (Fig. 10A).
Comparing the transgressive-regressive cycles in light of the chemostrati-
graphic correlation presented herein, a maximum transgression in the
Keyser Formation was synchronous through at least the southern outcrop
belt. Another maximum transgression in the Mandata Member appears to
coincide with that in the Kalkberg-New Scotland Formations of New York.
Otherwise, transgressive-regressive cycles do not appear to correlate across
the basin. We therefore conclude that local factors such as tectonics and
sediment supply were the dominant control on depositional patterns in the
Appalachian Basin at this time.
A positive carbon isotope excursion requires either addition of 13C or
removal of 12C. As a possible cause of the Klonk excursion, Malkowski
and Racki (2009) suggested that the expansion of land plants resulted in
burial of organic matter rich in 12C in epicontinental seas. The Winfield
section records oxygen limitation and enhanced burial of organic matter in
the Mandata Member. However, that unit is 9 m above the peak of the
positive isotope excursion, having been deposited after rather than before
or during the excursion as would be expected for organic-rich units that
could have contributed to the positive excursion. Saltzman (2002) noted
that the carbon isotope excursion in West Virginia coincides with a relative
sea-level lowstand and suggested that the lowered sea level could have
exposed and caused increased erosion of 13C-rich Silurian carbonate strata.
The correlation presented herein using carbon isotope data does not show a
synchronous lowstand throughout the Appalachian Basin (Fig. 10A).
However, because transgressive-regressive cycles appear to reflect local
rather than regional or global sea-level changes, a finer scale than the
forces that would have governed global carbon isotope trends, this does not
disprove Saltzman’s (2002) hypothesis. Additional stratigraphic studies
reporting high-resolution isotopic, geochronologic, and lithologic data
from late Silurian–Early Devonian sections are needed to fully characterize
and interpret the Klonk excursion.
CONCLUSIONS
At a time when global atmospheric and surface-water oxygen levels
were rising, there is evidence for oxygen limitation in the Appalachian
Basin. Strata at Winfield Quarry are interpreted to document a range of
depositional oxygenation conditions. Normal marine conditions are
interpreted for biomicrite with abundant, diverse fauna. Progressively
lower oxygenation is interpreted for facies from gray micrite with
Zoophycos burrows to gray shale with Chondrites burrows and limited,
sparse fauna to black, barren shale.
Facies distribution in the stratigraphic section reveals parts of three
transgressive-regressive cycles: (1) The Tonoloway Formation with
intertidal to supratidal laminated, mudcracked, evaporitic micrites
represents the tail end of a regression; (2) The Byers Island and Jersey
Shore Members of the Keyser Formation are biomicrites with sponge-
coral-crinoid biostromes that indicate a return to normal marine conditions
and overall transgression. The La Vale Member of the Keyser Formation
contains fossils that are increasingly abraded upsection and culminates in
micrites with mudcracks and tidal bedding, indicating regression and a
return to an intertidal to supratidal setting; and (3) The New Creek-
Corriganville Members of the Old Port Formation are a variety of shallow-
water facies that, above a basal bed of in situ stromatolites, lack indicators
of subaerial exposure or tidal influence; this records transgression to a
subtidal, above fair-weather wave base setting. An abrupt shift to mainly
black, barren shales in the lower Mandata Member indicates rapid
deepening to an oxygen-limited environment below storm wave base.
Upper Mandata Member mainly gray shales with Chondrites traces and a
limited fossil assemblage and Shriver Member micrites with Zoophycos
traces were deposited under continued but decreasing levels of oxygen
limitation, likely related to regression. This trend culminates with a return
to normal marine conditions, as shown in Ridgeley Member biomicrites
deposited below fair-weather wave base.
The Klonk Event positive carbon isotope excursion is recorded in
central Pennsylvania as a rise from a minimum of -4.3% in the Tonoloway
Formation to a high ofþ4.4% in the upper part of the La Vale Member of
the Keyser Formation, then a drop .5% to a low in the Mandata Member
of the Old Port Formation. Using trends observed in this globally
coincident data to correlate regionally, following methodology from
Husson et al. (2016) and incorporating their data, shows that the Keyser
Formation is equivalent to the Keyser and Tonoloway Formations in West
Virginia and parts of the Rondout, Manlius, and Coeymans Formations in
New York. The New Creek-Corriganville Members at Winfield Quarry are
mostly equivalent to the New Creek Formation in West Virginia and parts
of the Kalkberg and New Scotland Formations in New York. The Mandata
Member is equivalent to at least part of the Corriganville Formation in
West Virginia and parts of the Kalkberg, New Scotland, and Becraft
Formations in New York. This new correlation is more consistent with
other time-correlative markers, including conodont biostratigraphy and
volcanic-ash chronostratigraphy.
Interpreted transgressive-regressive trends do not match between West
Virginia, Pennsylvania, and New York when correlated using existing
lithostratigraphic correlation or the carbon-isotope correlation presented
here incorporating data from Pennsylvania. It is inferred that local
(tectonics, sediment supply) rather than global (eustatic) controls
dominated depositional patterns in the Silurian–Devonian boundary
interval in the Appalachian Basin.
ACKNOWLEDGMENTS
Thank you to Eastern Industries for allowing access to their quarry, without
which this project would not have been possible, and especially Albert Mabus
who facilitated that access daily. Many thanks to Dr. Patrick McLaughlin for his
important scientific contributions and guidance. Drs. Carmala Garzione and
Penny Higgins at the University of Rochester generously provided time and
guidance during geochemical analyses. The Geological Society of America
provided financial support for analyses. Dr. Tony Ekdale helped classify trace
fossils, and Dr. Carl Brett helped classify macrofossils. Special thanks to Eric
Lynch for his numerous contributions in the field and lab. Thank you also to Dr.
Matthew Saltzman and an anonymous reviewer for their thoughtful reviews of
this manuscript.
SUPPLEMENTAL MATERIAL
Data are available from the PALAIOS Data Archive:
https://www.sepm.org/supplemental-materials.
REFERENCES
BALDWIN, B. AND BUTLER, C.O., 1985, Compaction curves: American Association of
Petroleum Geologists Bulletin, v. 69, p. 622–626.
BELAK, R., 1980, The Cobleskill and Akron Members of the Rondout Formation: late
Silurian carbonate shelf sedimentation in the Appalachian Basin, New York State:
Journal of Sedimentary Petrology, v. 50, p. 1187–1204.
SEDIMENTOLOGY AND ISOTOPE STRATIGRAPHY OF SILURIAN–DEVONIAN STRATAP A L A I O S 421
Downloaded from https://pubs.geoscienceworld.org/sepm/palaios/article-pdf/34/9/405/4837049/i0883-1351-34-9-405.pdfby Rutgers University useron 14 October 2019
BELL, S.C. AND SMOSNA, R., 1998, Pridoli sea-level fluctuations and sequence stratigraphy
in the Appalachian Basin, USA: Southwestern Geology, v. 38, p. 259–278.
BRETT, C.E., DICK, V.B., AND BAIRD, G.C., 1991, Comparative taphonomy and paleoecology
of Middle Devonian dark gray and black shale facies from western New York, in E.
Landing and C.E. Brett (eds.), Dynamic Stratigraphy and Depositional Environments of
the Hamilton Group (Middle Devonian) in New York State, Part II: New York State
Museum/Geological Survey Bulletin Number 468, Albany, p. 5–36.
BRETT, C.E., GOODMAN, W.M., AND LODUCA, S.T., 1990, Sequences, cycles, and basin
dynamics in the Silurian of the Appalachian Foreland Basin: Sedimentary Geology, v.
69, p. 191–244.
BROMLEY, R.G. AND EKDALE, A.A., 1984, Chondrites: a trace fossil indicator of anoxia in
sediments: Science, v. 224, p. 872–874.
BUGGISCH, W. AND JOACHIMSKI, M.M., 2006, Carbon isotope stratigraphy of the Devonian of
central and southern Europe: Palaeogeography, Palaeoclimatology, Palaeoecology, v.
240, p. 68–88.
BUGGISCH, W. AND MANN, U., 2004, Carbon isotope stratigraphy of Lochkovian to Eifelian
limestones from the Devonian of central and southern Europe: International Journal of
Earth Science, v. 93, p. 521–541.
COHEN, K.M., HARPER, D.A.T., GIBBARD, P.L., AND FAN, J.-X., 2018, The ICS international
chronostratigraphic chart: Episodes, v. 36, p. 199–204.
COLE, S.R., HAYNES, J.T., LUCAS, P.C., AND LAMBERT, R.A., 2015, Faunal and
sedimentological analysis of a latest Silurian stromatoporoid biostrome from the central
Appalachian Basin: Facies, v. 61, 16 p., doi: 10.1007/s10347-015-0440-x.
COPLEN, T. B., 1994, Reporting of stable hydrogen, carbon, and oxygen isotopic
abundances: Pure and Applied Chemistry, v. 66, p. 273–276.
DENKLER, K.E. AND HARRIS, A.G., 1988, Conodont-based determination of the Silurian–
Devonian boundary in the Valley and Ridge Province, northern and central
Appalachians, in W.J. Sando (ed.), Shorter contributions to paleontology and
stratigraphy: U.S. Geological Survey Bulletin 1837, Washington, p. B1–B13.
DIEDRICH, N.W. AND WILKINSON, B.H., 1999, Depositional cyclicity in the Lower Devonian
Helderberg Group of New York State: Journal of Geology, v. 107, p. 643–658.
DOROBEK, S.L. AND READ, J.F., 1986, Sedimentology and basin evolution of the Siluro-
Devonian Helderberg Group, central Appalachians: Journal of Sedimentary Petrology, v.
56, p. 601–613.
EBERT, J.R. AND MATTESON, D.K., 2003, Distal stratigraphic effects of the Laurentia-Avalon
collision: a record of early Acadian (Prıdolı-Lochkovian) tectonism in the Helderberg Group
of New York State, USA: CFS Courier Forschungsinstitut Senckenberg, v. 242, p. 157–167.
EKDALE, A.A., 1988, Pitfalls of paleobathymetric interpretations based on trace fossil
assemblages: PALAIOS, v. 3, p. 464–472.
EPSTEIN, A.G., EPSTEIN, W.J., SPINK, W.J., AND JENNINGS, D.S., 1967, Upper Silurian and
Lower Devonian stratigraphy of northeastern Pennsylvania, New Jersey, and southeast-
ernmost New York: United States Geological Survey, Bulletin 1243, 83 p., doi: 10.7282/
T3WQ039P.
FREY, R.W., PEMBERTON, S.G., AND SAUNDERS, T.D.A., 1990, Ichnofacies and bathymetry: a
passive relationship: Journal of Paleontology, v. 64, p. 155–158.
HAQ, B.U. AND SCHUTTER, S.R. 2008, A chronology of Paleozoic sea-level changes,
Science, v. 322, p. 64–68.
HATCHER, R.D., JR., 2010, The Appalachian orogen: a brief summary, in R.P. Tollo, M.J.
Bartholomew, J.P. Hibbard, and P.M Karabinos (eds.), From Rodinia to Pangea: The
Lithotectonic Record of the Appalachian Region: Geological Society of America
Memoir 206, p. 1–19, doi: 10.1130/2010.1206(01).
HEAD, J.W., III, 1969, An integrated model of carbonate depositional basin evolution: late
Cayugan (upper Silurian) and Helderbergian (Lower Devonian) of the central
Appalachians: Unpublished Ph.D. dissertation, Brown University, Providence, 388 p.
HELFRICH, C.T., 1978, A conodont fauna from the Keyser Limestone of Virginia and West
Virginia: Journal of Paleontology, v. 52, p. 1133–1142.
HESS, A.V., 2008, Sedimentological and geochemical analysis of the Keyser and Old Port
Formations, central Pennsylvania: improved constraints on late Silurian–Early Devonian
paleoenvironmental conditions: Unpublished B.Sc. thesis, Bucknell University, Lewis-
burg, Pennsylvania, 79 p.
HUSSON, J.M., SCHOENE, B., BLUHER, S., AND MALOOF, A.C., 2016, Chemostratigraphic and
U-Pb geochronologic constraints on carbon cycling across the Silurian–Devonian
boundary: Earth and Planetary Science Letters, v. 436, p. 108–120.
IMMENHAUSER, A., DELLA PORTA, G., KENTER, J.A.M., AND BAHAMONDE, J.R., 2003, An
alternative model for positive shifts in shallow-marine carbonate d13C and d18O:
Sedimentology, v. 50, p. 953–959.
INNERS, J.D., 1981, Geology and mineral resources of the Bloomsburg and Mifflinville
quadrangles and part of the Catawissa Quadrangle, Columbia County, Pennsylvania:
Pennsylvania Bureau of Topographic and Geologic Survey Fourth Series Atlas 164cd,
152 p.
INNERS, J.D., 1997, Geology and mineral resources of the Allenwood and Milton
quadrangles, Union and Northumberland Counties, Pennsylvania: Pennsylvania
Geological Survey Fourth Series Atlas 144cd, 135 p.
JOHNSON, J.G., 1971, Timing and coordination of orogenic, epeirogenic, and eustatic events:
Geological Society of America Bulletin, v. 82, p. 3263–3298.
KAMMER, T.W., BRETT, C.E., BOARDMAN, D.R. II, AND MAPES, R.H., 1986, Ecologic stability
of the dysaerobic biofacies during the late Paleozoic: Lethaia, v. 19, p. 109–121.
KING, P.B., BEIKMAN, H.M., AND EDMONSTON, G.J., 1974, Geologic map of the United States
(exclusive of Alaska and Hawaii): U.S. Geological Survey, Denver, doi: 10.3133/7013
6641.
KENRICK, P., WELLMAN, C.H., SCHNEIDER, H., AND EDGECOMBE, G.D., 2012, A timeline for
terrestrialization: consequences for the carbon cycle in the Paleozoic: Philosophical
Transactions of the Royal Society B, v. 367, p. 519–536.
KENT, D.V. AND VAN DER VOO, R., 1990, Palaeozoic palaeogeography from palae-
omagnatism of the Atlantic-bordering continents, in W.S. McKerrow and C.R. Scotese
(eds.), Palaeozoic Palaeogeography and Biogeography: Geological Society of London,
Memoir 12, p. 49–56.
KLEFFNER, M.A., BARRICK, J.E., EBERT, J.R., MATTESON, D.K., AND KARLSSON, H.R., 2009,
Conodont biostratigraphy, d13C chemostratigraphy, and recognition of the Silurian/
Devonian boundary in the Cherry Valley, New York region of the Appalachian Basin, in
D.J. Over (ed.), Conodont Studies Commemorating the 150th Anniversary of the First
Conodont Paper (Pander, 1856) and the 40th Anniversary of the Pander Society, v. 62, p.
57–73.
LAPORTE, L.F., 1969, Recognition of a transgressive carbonate sequence within an epeiric
sea: Helderberg Group (Lower Devonian) of New York State, in G.M. Friendman (ed.),
Depositional environments in carbonate rocks: SEPM Special Publication 14, Tulsa, p.
98–119.
LENTON, T.M., DAHL, T.W., DAINES, S.J., MILLS, B.J.W., OZAKI, K., SALTZMAN, M.R., AND
PORADA, P., 2016, Earliest land plants created modern levels of atmospheric oxygen:
Proceedings of the National Academy of Sciences, v. 113, p. 9704–9709.
LOGAN, B.W., REZAK, R., AND GINSBURG, R.N., 1964, Classification and environmental
significance of algal stromatolites: Journal of Geology, v. 72, p. 68–83.
LU, W., RIDGWELL, A., THOMAS, E., HARDISTY, D.S., LUO, G., ALGEO, T.J., SALTZMAN, M.R.,
GILL, B.C., SHEN, Y., LING, H.-F., EDWARDS, C.T., WHALEN, M.T., ZHOU, X., GUTCHESS,
K.M., JIN, L., RICKABY, R.E.M., JENKYNS, H.C., LYONS, T.W., LENTON, T.M., KUMP, L.R.,
AND LU, Z., 2018, Late inception of a resiliently oxygenated upper ocean: Science, v. 361,
p. 173–177.
MALKOWSKI, K. AND RACKI, G., 2009, A global biogeochemical perturbation across the
Silurian–Devonian boundary: ocean-continent-biosphere feedbacks: Palaeogeography,
Palaeoclimatology, Palaeoecology, v. 276, p. 244–254.
MALKOWSKI, K., RACKI, G., DRYGANT, D., AND SZANIAWSKI, H., 2009, Carbon isotope
stratigraphy across the Silurian–Devonian transition in Podolia, Ukraine: evidence for a
global biogeochemical perturbation: Geological Magazine, v. 146, p. 674–689.
MARINTSCH, E.J. AND FINKS, R.M., 1978, Zoophycos size may indicate environmental
gradients: Lethaia, v. 11, p. 273–279.
MCADAMS, N.E.B., SCHMITZ, M.D., KLEFFNER, M.A., VERNIERS, J., VANDENBROUCKE, T.R.A.,
EBERT, J.R., AND CRAMER, B.D., 2017, A new, high-precision CA-ID-TIMS date for the
‘Kalkberg’ K-bentonite (Judd Falls Bentonite): Lethaia, v. 51, p. 344–356, doi: 10.1111/
let.12241.
MCLAUGHLIN, P.I., EMSBO, P., AND BRETT, C.E., 2012, Beyond black shales: the sedimentary
and stable isotope records of oceanic anoxia events in a dominantly oxic basin (Silurian;
Appalachian Basin, USA): Palaeogeography, Palaeoclimatology, Palaeoecology, v. 367-
368, p. 153–177.
MILES, C.E. (compiler), 2003, Geologic shaded-relief map of Pennsylvania: Pennsylvania
Geological Survey 4th Series Map 67.
MILUNICH, K.C. AND EBERT, J.R., 1993, Conodonts and K-bentonites in the Helderberg
Group (L. Dev., New York): an opportunity for time-scale calibration in eastern North
America: Geological Society of America Abstracts with Programs, v. 25, p. 65.
MOUNT, V.S., 2014, Structural style of the Appalachian Plateau fold belt, north-central
Pennsylvania: Journal of Structural Geology, v. 69, p. 284–303.
NATEL, E.M., JOHANNESSEN, K.L., MATTESON, D.K., DAMON, K., AND EBERT, J.R., 1996,
Upper Silurian–Lower Devonian conodont biostratigraphy of the upper Salina and lowest
Helderberg groups of central New York: Geological Society of America Abstracts with
Programs, v. 28, p. A-172.
PATTERSON, W.P. AND WALTER, L.M., 1994, Depletion of 13C in seawater RCO2 on modern
carbonate platforms: significance of the carbon isotopic record of carbonates: Geology, v.
22, p. 885–888.
POMAR, L., 2001, Types of carbonate platforms: a genetic approach: Basin Research, v. 13,
p. 313–334.
RICKARD, L.V., 1962, Late Cayugan (upper Silurian) and Helderbergian (Lower Devonian)
stratigraphy in New York: New York State Museum and Science Service Bulletin 386,
Albany, 157 p.
RIDING, R., 1999, The term stromatolite: towards an essential definition: Lethaia, v. 32, p.
321–330.
RODGERS, J., 1967, Chronology of tectonic movements of the Appalachian region of eastern
North America: American Journal of Science, v. 265, p. 408–427.
SALTZMAN, M.R., 2002, Carbon isotope (d13C) stratigraphy across the Silurian–Devonian
transition in North America: evidence for a perturbation of the global carbon cycle:
Palaeogeography, Palaeoclimatology, Palaeoecology, v. 187, p. 83–100.
SALTZMAN, M.R., 2005, Phosphorus, nitrogen, and the redox evolution of the Paleozoic
oceans: Geology, v. 33, p. 573–576.
SALTZMAN, M.R. AND EDWARDS, C.T., 2017, Gradients in the carbon isotopic composition of
Ordovician shallow water carbonates: a potential pitfall in estimates of ancient CO2 and
O2: Earth and Planetary Science Letters, v. 464, p. 46–54.
A.V. Hess and J.M. Trop422 P A L A I O S
Downloaded from https://pubs.geoscienceworld.org/sepm/palaios/article-pdf/34/9/405/4837049/i0883-1351-34-9-405.pdfby Rutgers University useron 14 October 2019
SMITH, R.C., II, AND WAY, J.H., 1988, The Bald Hill bentonite beds: a Lower Devonian
pyroclastic-bearing unit in the northern Appalachians: Northeastern Geology, v. 10, p.
216–230.
SMOSNA, R., 1988, Paleogeographic reconstruction of the Lower Devonian Helderberg
Group in the Appalachian Basin, in Devonian of the World: Proceedings of the
Second International Symposium on the Devonian System, Memoir 14, Volume 1:
Regional Syntheses: Canadian Society of Petroleum Geologists, Calgary, p. 265–
275.
SMOSNA, R. AND PATCHEN, D., 1978, Silurian evolution of central Appalachian Basin:
American Association of Petroleum Geologists Bulletin, v. 62, p. 2308–2328.
SMOSNA, R.A., PATCHEN, D.G., WARSHAUER, S.M., AND PERRY, W.J., JR, 1976, Relationships
between depositional environments, Tonoloway Limestone, and distribution of
evaporites in the Salina Formation, West Virginia, in Report of Investigations 28, Reefs
and Evaporites: Concepts and Depositional Models: West Virginia Geological and
Economic Survey, Morgantown, p. 125–143.
STEIN, R., 1986, Organic carbon and sedimentation rate: further evidence for anoxic deep-
water conditions in the Cenomanian/Turonian Atlantic Ocean: Marine Geology, v. 72, p.
199–209.
TUCKER, R.D., BRADLEY, D.C., VER STRAETEN, C.A., HARRIS, A.G., EBERT, J.R., AND
MCCURCHEON, S.R., 1998, New U-Pb zircon ages and the duration and division of
Devonian time: Earth and Planetary Science Letters, v. 158, p. 175–186.
VER STRAETEN, C.A., 2007, Basinwide stratigraphic synthesis and sequence stratigraphy,
upper Pragian, Emsian and Eifelian stages (Lower to Middle Devonian), Appalachian
Basin, in R.T. Becker and W.T. Kirchgasser (eds.), Devonian Events and Correlations:
Geological Society of London Special Publication 278, p. 39–81.
VER STRAETEN, C.A., 2008, Volcanic tephra bed formation and condensation processes: a
review and examination from Devonian stratigraphic sequences: Journal of Geology, v.
116, p. 545–557.
VER STRAETEN, C.A., 2009, The classic Devonian of the Catskill front: a foreland basin
record of Acadian orogenesis, in F. Vollmer (ed.), 81st Annual Meeting Guidebook,
Chapter 7: New York State Geological Association, Albany, p. 7-1–7-54.
VER STRAETEN, C.A., BRETT, C.E., AND SAGEMAN, B.B., 2011, Mudrock sequence
stratigraphy: a multi-proxy (sedimentological, paleobiological and geochemical)
approach, Devonian Appalachian Basin: Palaeogeography, Palaeoclimatology, Palae-
oecology, v. 304, p. 54–73.
VRAZO, M.B., TROP, J.M., AND BRETT, C.E., 2014, A new eurypterid Lagerstatte from the
upper Silurian of Pennsylvania: PALAIOS, v. 29, p. 431–448.
WALKER, K.R., SHANMUGAM, G., AND RUPPEL, S.C., 1983, A model for carbonate to
terrigenous clastic sequences, Geological Society of America Bulletin, v. 94, p. 700–712.
WEISSERT, H., JOACHIMSKI, M., AND SARNTHEIN, M., 2008, Chemostratigraphy: Newsletters
on Stratigraphy, v. 42, p. 145–179.
WITZKE, B.J., 1990, Palaeoclimatic constraints for Palaeozoic palaeolatitudes of Laurentia
and Euramerica, in W.S. McKerrow and C.R. Scotese (eds.), Palaeozoic Palae-
ogeography and Biogeography: Geological Society of London Memoir 12, p. 57–73.
Received 17 February 2019; accepted 10 August 2019.
SEDIMENTOLOGY AND ISOTOPE STRATIGRAPHY OF SILURIAN–DEVONIAN STRATAP A L A I O S 423
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