Orchard Beach, Pelham BayVirtual Field TripWhere are.docx

Orchard Beach, Pelham Bay
Virtual Field Trip
Where are we going?
• Orchard Beach at Pelham Bay
Park in Bronx, Northernmost
borough of NYC
• From the parking lot, walk on
the gravel path past tennis
courts toward the sound, then
walk NE along the beach to Twin
Islands
• This 10-20 minute walk will
include several stops
What are we going to see?
• Hartland formation: exotic terrane
(islands off the coast of Africa) that
collided with North America ~440 ma
• Devonian intrusions into the Cambro-
Ordovician rocks
• Evidence of glaciation (Wisconsin ice

sheet, 1000 ft thick in this part of NY, ~11
ka -80 ka)
• Sediments that were metamorphosed
during Taconic and Acadian orogenies
• Quartz-feldspar gneiss, biotite-sillimanite
schist, amphibolite
• Glacial till, glacial erratics, striations,
outwash plain, terminal moraine in the
distance
Map of NYC geology – US geological Survey
Tectonic evolution of the east coast:
• Follow along with this cartoon version of the
area’s tectonic history in your handout
• Overview:
• Grenville Orogeny completed the assembly of
Rodinia, ~1.5-1 ba
• Post-Grenville rifting created Iapetus ocean
• Iapetus ocean started closing
• Three pulses of Appalachian mountain building,
Taconian, Acadian, and Alleghanian orogenies,
close Iapetus Ocean
• Pangea breaks up in the Mesozoic, rifting creates
Atlantic ocean

• In this field trip we have glimpses into two of
the three pulses of Appalachian mountain-
building during early stages of Iapetan
closure: the Taconic Orogeny (Cambro-
Ordovician), and the Acadian Orogeny (late
Devonian)
Adapted from Earth: Portrait of a Planet by Steve
Marshak
Glaciation and 1st stop
• The top stratigraphic layers are much
younger than the tectonic events
described in the previous slide
• Ice age in the Pleistocene shaped
landscape, modified drainage, and eroded
strata
• Last advance of ice: Wisconsin stage of
the Laurentide ice sheet
• Terminal moraine at the edge of the ice
sheet creates Long Island
• Long Island Sound was a glacial lake; as
climate warmed and sea level rose, the
outwash lake became an estuary then a
sound; tall points of the moraine are now
islands

2nd stop: Hartland formation
• Hartland formation: exotic terrane
(islands off the coast of Africa) that
collided with North America ~440 ma
• Sediments that were metamorphosed
during two of the three pulses of
Appalachian mountain building:
Taconic and Acadian orogenies (check
tectonic evolution cartoon in your
handout)
• Quartz-feldspar gneiss, biotite-
sillimanite schist, amphibolite
• Follow the links; hope you can hear
me over the wind!
• https://youtu.be/aXcqGEgAH2k
• Severe deformation
• Partial melting of the schists and
gneiss produced abundant quartz-
feldspar leucosomes
• Leucosomes: lenticular shape, coarse-
grained, variable thickness, high-grade
metamorphism product
• Garnets: metamorphic index mineral
• https://youtu.be/j8YZUQWN1j4
https://youtu.be/aXcqGEgAH2k

https://youtu.be/j8YZUQWN1j4
Close up of garnet
porphyroblasts
Cavities left by dissolution
of calcite in amphibolite
Folded leucosomes in the Hartland formation
Glacial landscape
• Glacial grooves and striations in
Hartland formation
• https://youtu.be/U8yFnGqG9A0
• Unconformity: glacial till
overlying the Hartland formation
• https://youtu.be/tq-sIopV3Uw
Glacial erratics at Orchard Beach
https://youtu.be/U8yFnGqG9A0
https://youtu.be/tq-sIopV3Uw
Devonian dikes with straight planar boundaries, unaffected by
tight folding that deformed Taconian leucosomes
• https://youtu.be/NzwoYABulsw •
https://youtu.be/UWDHv9_ogCI

Note glacially formed Long Island Sound in the
background; Long Island, across the sound, is a terminal
moraine
Cross-cutting relationships – Devonian dikes intrude
Cambro-Ordovician Hartland rock
https://youtu.be/NzwoYABulsw
https://youtu.be/UWDHv9_ogCI
Metamorphosed turbidites
• Rhythmically bedded sequences
of gneiss and schist occur; these
are interpreted as turbidites,
deposits from sediment-laden
flows spewed into deep water.
On the northwestern side of
North Twin Island, graded
bedding is preserved, allowing
us to deduce the direction of
stratigraphic tops
• https://youtu.be/z1Tl1BnZVho
• The last hurrah – more cross-
cutting relationships:
• https://youtu.be/iJAVnPGg5v0
https://youtu.be/z1Tl1BnZVho
https://youtu.be/iJAVnPGg5v0

Thank you
• To my son Lev for his phone camera wielding skills
• To all of you for coming along on this virtual trip with me
• References:
• https://pbisotopes.ess.sunysb.edu/reports/ny-city/
• http://geologycafe.com/nyc/common/captions.htm
• https://blogs.agu.org/mountainbeltway/2010/03/25/transect-
debrief-5-
sedimentation-continues/
• http://www.geo.hunter.cuny.edu/courses/geog260/PP5-
2011Glaciation.pdf
Contributions to the Paleontology of New Jersey (II)
106
STOP 5: GINGERBREAD CASTLE STROMATOLITES,
HAMBURG, NJ
Deborah Freile1, Emma C. Rainforth2, and Gregory Herman3
1Department of Geoscience and Geography, New Jersey City
University, 2039 Kennedy Blvd.,
Jersey City, NJ 07305; [email protected]
2Environmental Science, Ramapo College of New Jersey, 505
Ramapo Valley Road, Mahwah,
NJ 07430; [email protected]
3New Jersey Geological Survey, P.O. Box 425, Trenton, NJ

08625;
[email protected]
Collecting is not permitted at this outcrop.
Leave hammers in the buses.
LOCATION
Hamburg 7.5 minute quadrangle.
This spectacular outcrop is on private property; permission to
visit must be obtained from Diversified
Communities. Hammering is not permitted (and would ruin the
outcrop for future visitors).
Use caution on the outcrop; surfaces are steep and may be
slippery. Excellent examples of features
described may be seen at the base of each slope.
INTRODUCTION
This spectacular outcrop is of stromatolitic Allentown Dolomite
(Middle Cambrian – lowermost
Ordovician), a shallow water, nearshore carbonate that was
periodically subaerially exposed.
Dolomitization of the original carbonate preserved many of the
original textures (Monteverde 2004). The
outcrop consists of ‘whalebacks’ – roche moutonnées carved by
glaciers, with the strata dipping to the
northwest (Figure 1).

Figure 1. View of outcrop prior to present construction. Ground
level is currently slightly lower and the
right end of the outcrop has been removed, permitting
examination of the outcrop in cross-section.
GANJ XXIV Annual Conference and Field Trip
107
STROMATOLITES
Stromatolites are ‘discrete, in-place structures with
recognizable boundaries that are characterized
by “gravity-defying” internal laminae reflecting addition of
material to a discrete surface’ (Demicco and
Hardie, 1994, p. 104). These cyanobacterial three-dimensional
laminated structures first appeared ~3.5
Ga, peaking 1.65 – 0.65 Ga; they declined dramatically after the
Early Ordovician, coinciding with the
increase in epifaunal grazers and burrowers (Demicco and
Hardie 1994). They are generally classified as
1) laterally linked hemispheroids, 2) discrete vertically stacked
hemispheroids or 3) discrete spheroids
(Logan et al., 1964). Combinational forms also exist. The term
thrombolite (Aitken, 1967) was proposed
for structures without discrete laminations. Stromatolites today

form in a variety of settings, including
shallow subtidal, intertidal and supratidal marine environments
or in saline lacustrine environments. In
salt ponds these features tend to be flat laminations instead of a
more three dimensional feature (Cornee et
al. 1992).
The stromatolites (Figure 2) observed at this site are of the
discrete spheroidal type, which tend to
correlate with higher energy environments. The higher energy
environment is also reinforced by the many
storm layers present throughout the outcrop (Figures 3, 4).
These storm layers are rich in ooids .
Figure 2. Close-up of a portion of the uppermost bedding plane
in the outcrop. In the center of the picture
a collapse breccia is visible (see also Figure 3): material that
fell into a cavity following minor dissolution.
Immediately overlying this layer are mudcracked carbonates,
visible in darker area in lower right portion
of photograph; these indicate subaerial exposure at this time.
Glacial striations are clearly visible in most
of this photograph. Pencil for scale (adjacent to lower left
stromatolite).
108

Figure 3. Oolitic layers; the lower darker-colored layer contains
small ooids while the upper layer bears
much larger ooids. Dark gray rip-up clasts occur near the
interface of the two layers.
Figure 4. Edgewise conglomerate; pebbles are ripped up form
underlying layers.
109
Figure 5. Cross-sectional view of a collapse breccia associated
with dissolution of material in-between
stromatolite mounds.
Additionally, these mounds appear to be cut by tidal channels
and this can cause slumping that is filled by
bioclasts and lithoclasts which were originally reworked
desiccated tidal flat sediments (Figures 2, 5).
Analogous conditions are presented by Wilson (1975) from the
Late Cambrian algal mounds of central
Texas (Llano Uplift) as well as other areas throughout the edges
of the North American craton. The
outcrop also includes desiccation cracks (Figure 2), which

supposes an intertidal to even supratidal
environment. Desiccation cracks are characteristically
associated with microbialites in peritidal
environments (Burne and Moore, 1987). Both cyanobacterial
and algal mats can be responsible for the
formation of desiccation cracks in dolomitic sediments in the
modern tidal flats of the Bahamas (Mitchell
and Horton, 1995).
Diagenetically, the outcrop shows extensive stylolites and
fenestral porosity. Stylolites are pressure
solution secondary sedimentary structures, while fenestral
porosity and bird’s eye structures are
syndepositional structures mainly found in supratidal algal
related mud dominated sediments (Moore,
1989).
PALEOENVIRONMENTAL INTERPRETATION
We interpret this outcrop as having been formed in nearshore to
marginal marine conditions
(Figure 6). The presence of mudcracks, birds-eye structures, and
tidal channels indicate subaerial
exposure; the stromatolites and oolitic carbonates would have
formed in shallow water. The section
records several such fluctuations in base level.
GLACIAL FEATURES
The whaleback outcrops are glacially-carved roche moutonnées.
Glacial striations are evident over
most of the polished surfaces (Figure 1), and (along with the

outcrop orientation) indicate direction of
glacial flow. In places, chatter marks are visible.
110
Figure 6. Paleoenvironmental reconstruction of the Gingerbread
Castle stromatolite site. (Modified from
Pratt et al., 1992.)
HYDROGEOLOGY
A hydrogeological framework study was conducted by the New
Jersey Geological Survey at this
development as part of a ground-water supply investigation. The
well field at the development includes
one 8-inch diameter supply well and five 6-inch diameter
observation wells in bedrock. The bedrock
aquifer is composed of the lower part of the Allentown
Dolomite and the upper part of the Leithsville Fm.
A profile view (Figure 7) of the hydrogeological framework was
constructed based on optical televiewer,
fluid-temperature and electrical-conductivity, caliper, heat-
pulse flowmeter, and color video (VHS)
borehole geophysical logs. Stratigraphic bedding and tectonic
fracture orientations were measured using
an optical televiewer.

111
Figure 7. Hydrogeological framework of wellfield.
REFERENCES
Aitken, J.D., 1967. Classification and environmental
significance of cryptalgal limestones and dolomites,
with illustrations from the Cambrian and Ordovician of
southwestern Alberta. Journal of
Sedimentary Petrology 37: 1163-1179.
Burne, R.V. and Moore, L.S., 1987. Microbialites:
Organosedimentary deposits of benthic microbial
communities. Palaios 2: 241-254.
Cornee, A., Dickman, M., and Busson, G., 1992. Laminated
cyanobacterial mats in sediments of solar salt
works: Some sedimentological implications. Sedimentology 39:
599-612.
Demicco, R.V. and L.A. Hardie, 1994. Sedimentary Structures
and Early Diagenetic Features of Shallow
Marine Carbonate Deposits. SEPM Atlas Series No. 1, 265 pp.

Logan, B.W., Rezak, R., and Ginsburg, R.N., 1964.
Classification and environmental significance of algal
stromatolites. Journal of Geology 72: 68-83.
Mitchell, S.W. and Horton, R.A., 1995. Dolomitization of
modern tidal flat, tidal creek, and lacustrine
sediments, Bahamas. Pp. 201-221 in Curran, H.A. and White,
B., (eds.), Terrestrial and Shallow
Marine Geology of the Bahamas and Bermuda. Geological
Society of America Special Paper 300.
Monteverde, D.H., 2004. Stratigraphy and Correlation of the
Paleozoic sedimentary units of New Jersey:
Stop 6 - Allentown Dolomite, p. 87-91. In A.E. Gates (ed.),
2004 NAGT-ES Conference Field Trip
Guide. NAGT/Rutgers-Newark.
Moore, C.H., 1989. Carbonate Diagenesis and Porosity.
Elsevier, Amsterdam, 338 pp.
Pratt, B.R., James, N.P., and Cowan, C.A., 1992. Peritidal
Carbonates. Pp. 303-322 in Walker, R.G. and
James, N.P. (eds.), Facies Models. Geological Association of
Canada.
Wilson, J.L., 1975. Carbonate Facies in Geologic History.
Springer-Verlag, Heidelberg, 471 pp.
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(c) 2012 The American Association of Petroleum

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2
Paleogeography of the Great American

Carbonate Bank of Laurentia in the
Earliest Ordovician (Early Tremadocian):
The Stonehenge Transgression
James R. Derby1
Consultant, Leonard, Oklahoma, U.S.A.
Robert J. Raine2 and M. Paul Smith3
Lapworth Museum of Geology, University of Birmingham,
Edgbaston Birmingham, United Kingdom
Anthony C. Runkel
Minnesota Geological Survey, Saint Paul, Minnesota, U.S.A.
ABSTRACT
This chapter describes and presents a newly compiled map
illustrating the paleogeography
of Laurentia during the earliest Ordovician, a time when the
great American carbonate bank
was at one of its greatest extents and a period for which the
most is understood. The map
depicts the known or postulated extent of the inner detrital belt,
the great American carbon-
ate bank and the more problematic (commonly structurally
relocated) outer detrital belt. The
period on which the map is based and discussed in the
accompanying text is based on the
Early Ordovician (early Ibexian) (early Tremadocian)
Stonehenge transgression.
INTRODUCTION
In 1980, while Derby and Ginsburg were preparing

Ginsburg for his talk at the 1980 Society of Economic
Paleontologists and Mineralogists Research Confer-
ence on the Carbonate and Orthoquartzite Suite (Dott
and Byers, 1981), Ginsburg asked the questions, ‘‘Just
what was the extent of the great American (carbonate)
bank (GA[C]B)?’’ and ‘‘How broad was the GA(C)B?’’
At that time, no single map existed. In the process of
answering those questions again in 2010, Derby real-
ized that no modern platewide map of the original
extent of the GACB exists, 30 yr later.
To this day, authors continue to use a series of out-
dated maps, all of which were also available in 1980.
Many authors continue to use Kay’s famous map (1951).
5
Derby, James R., Robert J. Raine, Anthony C. Runkel, and M.
Paul Smith, 2012,
Paleogeography of the great American carbonate bank of
Laurentia in the earliest
Ordovician (early Tremadocian): The Stonehenge transgression,
in J. R. Derby,
R. D. Fritz, S. A. Longacre, W. A. Morgan, and C. A.
Sternbach, eds., The great
American carbonate bank: The geology and economic resources
of the Cambrian–
Ordovician Sauk megasequence of Laurentia: AAPG Memoir 98,
p. 5–13.

1Present address: Department of Geosciences, University of
Tulsa, Tulsa, Oklahoma, U.S.A.
2Present address: Ichron Ltd., Norwich, Cheshire, United
Kingdom.
3Present address: Oxford University Museum of Natural
History, Oxford, Oxfordshire, United Kingdom.
Copyright n2012 by The American Association of Petroleum
Geologists.
DOI:10.1306/13331487M983496
128.59.222.107 on Mar 24, 2017, 4:24 PM.
However, this map actually shows paleographic realms
of the lower Tippecanoe megasequence and nothing at
all of the Sauk megasequence. More accurate Sauk maps
by Reuben Ross (1976) also are widely used by authors,
including somein this volume. However, the Ross (1976)
map portrays only the western United States and parts
of Mexico.
All of North America is illustrated on the magnif-
icent maps in the Stratigraphic Atlas of North and Central
America (Cook and Bally, 1975). These maps do an
excellent job of portraying the present extent of existing
strata of the GACB, with some exceptions; they do not
include areas where the GACB sediments have been
removed by later erosion, nor those parts that have
drifted away. However, these maps do include areas
that were appended to North America much after Sauk

deposition, and, somewhat misleadingly for the pur-
poses of this volume, they show the facies of these
appendages to Laurentia. In many respects, these maps
are superior in detail to our current effort, but they also
contain some serious omissions and miscorrelations,
which the chapters in this volume will demonstrate. For
example, the Reelfoot rift basin and its sediments were
completely omitted.
CONSTRUCTION OF THE PALEOGEOGRAPHIC MAP
This map (Figure 1) was originally intended to be
used in an introductory summary chapter by Derby
and Ginsburg, with a review of the naming of the great
American carbonate bank (GACB) and the original
dilemma posed by Ginsburg in 1980 a review of what
we have learned to date, and a discussion of possible
depositional mechanisms for the sequences we observe.
The compilation of the map soon exceeded that original
intent and was judged to deserve a separate chapter.
The schematic map of Byers and Dott, presented
here as Figure 2, represents a period in the latest Cam-
brian and earliest Ordovician when the inner detrital
belt was at its maximum that likely corresponds, at
least in part, to a widely recognized lowstand—the
Lange Ranch lowstand (Miller et al., 2012). This leaves
the impression, correct for the period portrayed, that
the GACB was a narrow belt fringing Laurentia. For a
stratigraphic cross section illustrating this period, see
figure 3 of Runkel et al. (2012).
The earliest Ordovician map represents, however,
the probable near-maximum extent of the GACB dur-
ing the Stonehenge transgression. Figure 3 of Runkel
et al. (2012) also illustrates the extent of the Lower

Ordovician carbonates of the Gasconade Formation
(and its equivalents), which were deposited during the
Stonehenge transgression.
The schematic paleographic map of Figure 1 is highly
generalized, except in a few areas, where fairly precise
information is available. This map attempts to portray
the extent of the GACB at the time of the early Trem-
adocian or Stonehenge transgression (Taylor et al., 1992).
This probably does not represent the greatest maximum
transgression of the Sauk megasequence, but it is one
of the intervals that is most extensively preserved and
widely recognized. Because later maximum transgres-
sions are poorly preserved, if at all, on the cratonic
interior, the transition from the carbonate bank to the
inner detrital belt (IDB) is poorly known. For compar-
ison of well-documented Sauk sea level curves, see the
well-studied and nearly 100% exposed sections in west-
ern Utah’s Ibex-House Range, sections presented in
Miller et al. (2012), and the extrapolation of the Utah
curves into the Missouri Ozarks sequences presented by
Miller, in Palmer et al. (2012).
The generalized map of Figure 1 is not intended to
be a Global Information System-registered accurate-
to-the-mile summary of final results. State lines and in-
ternational borders are intentionally left off to under-
score an absence of precision. We have attempted to
summarize the general state of our knowledge, as dem-
onstrated in much greater detail in this volume.
Two possibly controversial innovations are on this
map. One is the lack of defined siliciclastic source area.
As Runkel points out in the discussion below, without
outcrop of the paleoshoreline, we really have no way of
knowing wherethe IDB ends and the source area begins,

so he showed the IDB and exposed land combined into
one map unit. The second issue is the removal of the
Transcontinental arch (TA) from this paleogeographic
map. For years, several experienced stratigraphers have
questioned the validity of the TA as a control on depo-
sition during the Cambrian and Ordovician. Myrow et al.
(2003) finally dispelled the myth. The TA is mostly an
artifact of uplift and erosion after Sauk deposition.
Following is a discussion of the degree of restoration
and sources of information for the map and the three
major facies belts as shown on the map (Figure 1). In
this discussion, compass directions and coordinates
will refer to modern maps, not to paleoreconstructions.
PALINSPASTIC AND CONTINENTAL
DRIFT RESTORATION
We have taken some liberties with this map, with the
result that the end product is somewhat uneven. The
North Atlantic region is shown with major restoration
of parts of Laurentia that have been dislocated sig-
nificantly by continental drift. In contrast, the western
6 Derby et al.
128.59.222.107 on Mar 24, 2017, 4:24 PM.
Figure 1. Restored extent of the great American carbonate bank
(GACB) during the earliest Ordovician (early Tremadocian)
Stonehenge transgression. This transgression occurred during

deposition of the Early Ordovician Symphysurina trilobite Zone
or
during deposition of the Cordylodus angulatus and basal
Rossodous manitouensis conodont Zones. This period probably
does
not represent the maximum transgression during deposition of
the Sauk III but is commonly preserved and recognized across
Laurentia. The records of younger transgressions, which may
have been more extensive, are commonly removed by erosion.
Consequently, this map records the maximum documented (at
this time) extent of the GACB across Laurentia.
Paleogeography of the Great American Carbonate Bank of
Laurentia 7
128.59.222.107 on Mar 24, 2017, 4:24 PM.
part of North America (modern coordinates) is shown
with no restorations at all because of the complexity
of the area and the mixture of translocated parts of
Laurentia and exotic terranes. In Alaska, some of the
terranes, although accurately dated and clearly delin-
eated, contain mixed faunas that cannot be ascribed to
Laurentia with certainty, so these terranes are omitted
from the map and indicated by question marks.
In other areas, a modest amount of palinspastic res-
toration is effected as in the Appalachians and in the
southern Oklahoma–Arkansas Ouachita region, where
seismic data provide a fair estimate of the amount of
subsequent overthrusting of the outer detrital belt (ODB)

over the great American carbonate bank (GACB) car-
bonate shelf.
Cuyania, the Argentine pre-Cordillera, is restored to
its postulated position adjacent to the Marathon and
Ouachita basins. This area clearly contains Cambrian
trilobites of Laurentian affinity but differs sufficiently
in lithofacies and its Ordovician fauna to suggest it is
slightly detached from the contiguous GACB (Dickerson,
2012; Keller, 2012). The outer margin of the Cuyania little
American carbonate bank is delineated by the Valle Fertil
lineament (VFL on Figure 1), beyond which no terranes
of Laurentian affinity are known.
Two parts of North America that were not part of
Laurentia are eliminated from the map: the Suwannee
terrane of Florida, Georgia, and Alabama and the region
of southern Mexico. The Suwannee terrane lies south of
the Suwannee terrane suture (STS on Figure 1). As sug-
gested by Bass (1969) and Rodgers (1970) and supported
by paleontologic evidence (Pojeta et al., 1976; Derby,
1982), the area is a fragment of western Africa left at-
tached to North America following the opening of the
modern Atlantic Ocean.
The complex southern margin of Laurentia in Mexico
is approximated by the position of the Walper mega-
shear, a Mesozoic feature. The map shows that position,
as drawn by Pessagno and Martin (2003).
THE INNER DETRITAL BELT AND SOURCE AREA
The inner detrital belt (IDB) (Palmer, 1960) represents
a suite of typical nearshore marine siliciclastic facies
that contain features reflecting the importance of both

wave- and tide-generated currents in the depositional
system. The facies range from relatively coarse-grained
shoreline deposits to offshore deposits dominated by
very fine grained sandstone, siltstone, and shale that
accumulated below fair-weather wave base. The IDB
is shown combined with exposed land in Figure 1 be-
cause the Lower Ordovician record is inadequate to
distinguish a discrete paleoshoreline, except in rela-
tively rare and localized areas of the continent.
The transitional area between the IDB and the GACB
throughout much of the Cambrian and earliest Or-
dovician (Figure 2) was commonly characterized by
relatively deep-water deposition recorded by mixed
carbonate and siliciclastic facies with condensation fea-
tures and other attributes indicative of suppressed car-
bonate productivity and starvation of siliciclastic sand.
The interfingering of both siliciclastic and carbonate
strata makes it difficult to establish an objective de-
finitive boundary between the IDB and GACB. The
boundary shown in Figure 1 is intended to generally
Figure 2. Byers and Dott (1995) map of
Laurentia during deposition of the latest
Cambrian Jordan Sandstone, published
with permission of SEPM. This map fairly
represents, at the degree of detail intended,
a period of the maximum extent of the
inner detrital belt and, therefore, a mini-
mum extent of the great American car-
bonate bank (GACB). 1000 km (621 mi).
8 Derby et al.
128.59.222.107 on Mar 24, 2017, 4:24 PM.

correspond to the interior edge of where Lower Or-
dovician strata are dominated by stacks of oolitic,
ribbon-rock, and microbialite carbonate facies that
typify much of the GACB.
Depiction of the outboard (paleoseaward) extent of
the IDB during the Stonehenge transgression is more
problematic in some respects than for previous times.
The pronounced continental-scale flooding during the
Stonehenge transgression led to onlap and deposition of
classic GACB facies across much more of craton than
during Cambrian flooding events. As a result, in many
places, the boundary between the IDB and GACB dur-
ing the Early Ordovician was located in relatively far
interior areas that no longer have a rock record for this
period. The cratonic interior extent of the GACB across
much of the map shown in Figure 1 might thus best be
considered a minimum landward extent.
GREAT AMERICAN CARBONATE BANK
The greatest dimensions of the GACB lie almost en-
tirely in the United States and Mexico. This truly great
carbonate bank has maximum dimensions of more than
3000 km (1860 mi) east to west (Nevada–Tennessee) and
1500 km (930 mi) north to south (Texas–Minnesota)
(Figure 1). Thickness ranges considerably depend on
location and stratigraphic units, from more than 5000 m
(>17,000 ft) in western Utah to a few hundreds of meters
in thinner parts. The carbonate bank apparently nar-
rows considerably in the western United States and

Canadian Cordillera and in the eastern United States
and the Canadian northern Appalachians, to 100 to 300
km (60–185 mi). The carbonate bank is once again much
broader in northern Canada and Greenland, reaching
a width of about 1000 km (�620 mi).
The continuity of the GACB along the Laurentian
margin from western Newfoundland, through Scot-
land to Greenland, can be deduced from the similarity
of the conodont fauna (Smith, 1991; Ji and Barnes,
1994; Raine, 2010) and its position before opening of
the North Atlantic has been based on the reconstruc-
tion by Higgins et al. (2001).
Scotland and Western Newfoundland
The eastern Laurentian (southern paleomargin) con-
sists of a series of promontories and reentrants (Lavoie
et al., 2003); with Scotland situated on a promontory
that marks a significant inflexion in the continental
margin (Thomas, 1977; Soper, 1994). These paleogeo-
graphic features suggest that the original shape of the
Iapetus margin reflects the interplay of rifting and oce-
anic transform faults (Soper, 1994; Lavoie et al., 2003).
The Baie Verte line represents the margin of Lauren-
tia in western Newfoundland and preserves ophiolite
suites and volcanic and volcaniclastic rocks thrust against
the GACB strata.
The Hebridean terrane rocks’ Durness Group of the
GACB in northwestern Scotland can be correlated with
the external Humber zone (Port au Port Group) of the
northern Appalachian orogen in western Newfound-
land (Williams, 1979). In northwestern Scotland, GACB
facies are preserved in the Hebridean terrane, one of

several terranes that lie north of the Iapetus suture. Clo-
sure of the Iapetus Ocean resulted in collision of island
arcs and, finally, Avalonia and Baltica with the margin
of Laurentia, forming these terranes. The exposed rocks
represent a succession preserved within the Caledonian
foreland. The Highland Boundary Fault marks the south-
ern margin of autochthonous Laurentian crust during
the Early Ordovician (Armstrong and Owen, 2001) and
continues into Ireland, where it is represented by the
Fair Head-Clew Bay line (Harper et al., 1989; Chew,
2003). With closure of the Iapetus Ocean, the Caledonide
mountain belt developed, and much of the GACB and
ODB were removed by thrusting and erosion.
A Scandian thrust fault (the Moine thrust) over-
rides the Ordovician GACB sediments of the Caledo-
nian foreland in Scotland, and although the margin
likely lays some distance to the southeast of the pre-
served Durness Group, it is now overlain by Precam-
brian metasediments and gneisses. The Durness Group
extends approximately 180 km (112 mi) in a northeast–
southwest direction and, because of the uniformity of
the stratigraphy and facies, the outcrop is interpreted
to be close to depositional strike.
Greenland and Svalbard
The GACB sediments of Greenland and Svalbard Ar-
chipelago (Stouge et al., 2012) present a complex picture
requiring considerable reconstruction.
The GACB deposits in Greenland are principally dis-
tributed along the modern-day north and east coasts,
although Ordovician sea level maximums did result in
the deposition of an unconformity-dominated succession
at Fossilik, West Greenland (Smith, 1988). On the east

coast, peritidal and shallow-subtidal carbonates ex-
tend in a belt for 1300 km (808 mi) from Scoreseby Sund
in the south to Kronprins Christian Land in the north
(Stouge et al., 2012). The succession is deformed by a
single phase of deformation, the Scandian, associated
with the main collision of Baltica and Laurentia (Smith
and Rasmussen, 2008). This deformation disrupted the
margin into a series of thrust sheets that accommodated
shortening of several hundred kilometers. The GACB
deposits are present in both the foreland, where they
Paleogeography of the Great American Carbonate Bank of
Laurentia 9
128.59.222.107 on Mar 24, 2017, 4:24 PM.
constitute an attenuated succession a few tens of meters
thick, and in the highest thrust sheet, where the subtidally
dominated GACB component of the Kong Oscar Fjord
Group is in excess of 4 km (13,000 ft) in thickness (Smith
and Rasmussen, 2008).
In North Greenland, from Kronprins Christian Land
in the east to Nares Strait in the west, GACB deposits
are part of the Franklinian Basin, which extends across
the strait into Arctic Canada for approximately 2000 km
(�1240 mi) in total. The Franklinian Basin in North
Greenland is a relatively undeformed part of the Lau-
rentian margin, with an infill that was deformed by the
Ellesmerian orogeny in the Devonian, but which has not
been affected by major collisions or margin-parallel strike-

slip tectonics (Higgins et al., 1991). The Franklinian mar-
gin preserves an inboard shallow-water shelf area with
GACB deposits up to 1 km (3300 ft) thick and an out-
board deep-water component of the basin, which was al-
ternately starved or filled by sand deposited by turbidity
currents and representative of the ODB. Although now
partoftheSvalbardArchipelago,theCambrian–Ordovician
rocks of Bjørnøya were deposited on the northeastern
extremity of this Franklinian shelf (Smith, 2000).
The Svalbard Archipelago is composed of Spitsbergen,
Nordaustlandet, Bjørnøya, and several other islands
and is generally considered to comprise three principal
terranes: the western, central, and eastern provinces of
Harland (1997). Bjørnøya has been considered to be part
of the central province but, as noted above, the stra-
tigraphy indicates that it was a constituent part of the
Laurentian margin until it was displaced on a strike-slip
fault before Atlantic opening (Smith, 2000).
Good evidence exists that the eastern province was
the outboard extension of the East Greenland margin
at the time of GACB deposition and was displaced to
its current location by late Caledonian strike-slip tec-
tonics. The succession preserves typical Cambrian–
Ordovician GACB carbonates, similar to the upper
allochthonous sheet in the Greenland Caledonides,
that are overlain by the ODB deep-water sediments
following the foundering of the shelf late in Sauk IV
deposition (Fortey and Barnes, 1977; Harland, 1997;
Smith and Rasmussen, 2008).
The western province of Spitsbergen has been com-
pared with North Greenland, but the correlation is not
secure and lacks stratigraphic detail. The most poorly
reconstructed terrane is the central province, which

has a thick Cambrian–Ordovician carbonate succession
with Laurentian affinity (Szaniawski, 1994; Harland,
1997), capped by even more poorly known turbidites
(Major and Winsnes, 1955). Its structural position sug-
gests that it lays inboard of the eastern province, but
it remains one of the most poorly known fragments of
the GACB.
Canada and Alaska
Dewing and Nowland (2012) describe five sequences
of GACB sediments in the Canadian Arctic, the fourth
of which contains Stairsian evaporites. In general, a
clearly defined shelf margin is preserved, with ODB
sediments occupying the off-shelf area. These sequences
extend from northwestern Greenland onto the Arctic
Lowland of mainland Canada and into the Jones Ridge
area of Alaska (Dumoulin and Harris, 2012; Pyle, 2012).
Several well-defined carbonate terranes in Alaska either
contain faunas of Siberian affinity or are of such uncertain
affinity that they are not ascribed herein to Laurentia.
In the Cordillera of western Canada, and south into
Montana and Idaho, the GACB constitutes a narrow
belt, but with a well-defined ODB to its west.
OUTER DETRITAL BELT
The ODB represents deeper water slope-and-ocean-
basin detrital sediments deposited outboard of the
GACB. The overall record of the ODB is somewhat
sketchy, as much of the ODB has been thrusted over
GACB sediments and subsequently removed by ero-
sion. We shall not attempt to document the ODB in
detail, but mention some major features and/or areas of
uncertainty.

The (modern) southern margin of the GACB is
marked by the Mesozoic Walper megashear in Mex-
ico and by the Marathon-Ouachita-Cuyania Basin ODB
sediments in the southern United States.
In the Appalachian trend, the ODB can be approx-
imated in the south by facies reconstruction (Read and
Repetski, 2012) but is represented by the Conestoga,
Lancaster, and Frederick Valley slope deposits in Penn-
sylvania and Maryland (Brezinski et al., 2012).
From eastern Pennsylvania to western Newfound-
land, the ODB is well preserved in the Taconic al-
lochthon (Landing, 2012; Lavoie et al., 2012). In New-
foundland, the ODB is also preserved. These sediments
comprise the allochthonous Cow Head and Northern
Head Groups (James and Stevens, 1986; Jameset al., 1989),
which represent ramp-margin and slope deposits.
The ODB sediments of Early Ordovician age are
not preserved in Scotland, but parts of the Dalradian
Supergroup (including the Cambrian Leny Limestone,
which comprises thinly bedded turbidite-deposited
limestones) within the Highland Border complex rep-
resent an older ODB of Laurentia (Fletcher and Rushton,
2008).
The transition from the GACB to the ODB is well
defined—from Northwest Greenland westward and
southward from the Arctic Islands of Canada through
10 Derby et al.
128.59.222.107 on Mar 24, 2017, 4:24 PM.

the Canadian Cordillera. Bush et al. (2012) describe the
complex transition from GACB sediments to the poorly
defined transition to the earliest Ordovician ODB in
northwestern United States. Similarly, the location of the
transition from the carbonates of the GACB to the ODB
during the Stonehenge transgression is shown as poorly
defined in most of western United States because of the
complexities of the region mentioned earlier.
ACKNOWLEDGMENTS
This map was compiled by the authors with advice
from Martin Keller, Pat Dickerson, Keith Dewing,
George Dix, John Taylor, John Repetski, and Svend
Stouge, and consultation with the many manuscripts
for this volume.
REFERENCES CITED
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of the paratectonic Caledonides of northern Britain: Jour-
nal of the Geological Society (London), v. 158, p. 475–486,
doi:10.1144/jgs.158.3.475.
Bass, M. N., 1969, Petrography and ages of crystalline rocks of
Florida: Some extrapolations: AAPG Memoir 11, p. 283–
310.
Brezinski, D. K., J. F. Taylor, and J. E. Repetski, 2012,
Sequential development of platform to off-platform
facies of the great American carbonate bank in the

central Appalachians, in J. R. Derby, R. D. Fritz, S. A.
Longacre, W. A. Morgan, and C. A. Sternbach, eds., The
great American carbonate bank: The geology and
economic resources of the Cambrian–Ordovician Sauk
megasequence of Laurentia: AAPG Memoir 98, p. 383–
420.
Bush, J. H., R. C. Thomas, and M. C. Pope, 2012, Sauk
megasequence deposition in northeastern Washington,
northern Idaho, and western Montana, in J. R. Derby,
Sternbach, eds., The great American carbonate bank: The
geology and economic resources of the Cambrian–
Ordovician Sauk megasequence of Laurentia: AAPG
Memoir 98, p. 751–768.
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positional sequences of the Jordan Formation (Upper
Cambrian), northern Mississippi Valley: Journal of Sedi-
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Chew, D. M., 2003, Structural and stratigraphic relation-
ships across the continuation of the Highland Boundary
Fault in western Ireland: Geological Magazine, v. 140,
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Cook, T. D., and A. W. Bally, 1975, eds., Stratigraphic atlas
of North and Central America: Princeton, New Jersey,
Princeton University Press, 272 p.
Derby, J. R., 1982, Northern Florida, in R. J. Ross, Jr., et al.,
The Ordovician System in the United States: Internation-
al Union of Geological Sciences Publication 12, 73 p.
Dewing, K., and G. Nowland, 2012, The Lower Cambrian to
Lower Ordovician carbonate platform and shelf-margin,

Canadian Arctic Islands, in J. R. Derby, R. D. Fritz, S. A.
Longacre, W. A. Morgan, and C. A. Sternbach, eds., The
great American carbonate bank: The geology and
economic resources of the Cambrian–Ordovician Sauk
megasequence of Laurentia: AAPG Memoir 98, p. 627–
647.
Dickerson, P. W., 2012, The circum-Laurentian carbonate bank,
the western Ouachita-Cuyania Basin, and the prodigal
Llanoria landmass, inJ.R. Derby, R. D.Fritz, S. A. Longacre,
W. A. Morgan, and C. A. Sternbach, eds., The great Amer-
ican carbonate bank: The geology and economic resources
of the Cambrian–Ordovician Sauk megasequence of Lau-
rentia: AAPG Memoir 98, p. 959–984.
Dott, Jr., R. H., and C. W. Byers, 1981, SEPM research con-
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Dumoulin, J. A., and A. G. Harris, 2012, Cambrian–
Ordovician sedimentary rocks of Alaska, in J. R. Derby,
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Ordovician Sauk megasequence of Laurentia: AAPG
Memoir 98, p. 649–673.
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fauna of the Leny Limestone, Perthshire, Scotland: Earth
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128.59.222.107 on Mar 24, 2017, 4:43 PM.
15
Sequential Development of Platform
to Off-platform Facies of the Great
American Carbonate Bank in the
Central Appalachians
David K. Brezinski
Maryland Geological Survey, Baltimore, Maryland, U.S.A.
John F. Taylor
Geoscience Department, Indiana University of Pennsylvania,
Indiana, Pennsylvania, U.S.A.
John E. Repetski
U.S. Geological Survey, Reston, Virginia, U.S.A.
ABSTRACT
In the central Appalachians, carbonate deposition of the great
American carbonate bank
began during the Early Cambrian with the creation of initial
ramp facies of the Vintage For-
mation and lower members of the Tomstown Formation.
Vertical stacking of bioturbated
subtidal ramp deposits (Bolivar Heights Member) and
dolomitized microbial boundstone
(Fort Duncan Member) preceded the initiation of platform
sedimentation and creation of a
sand shoal facies (Benevola Member) that was followed by the

development of peritidal
cyclicity (Dargan Member). Initiation of peritidal deposition
coincided with the development
of a rimmed platform that would persist throughout much of the
Cambrian and Early Ordo-
vician. At the end of deposition of the Waynesboro Formation,
the platform became subaerially
exposed because of the Hawke Bay regression, bringing the
Sauk I supersequence to an end. In
the Conestoga Valley of eastern Pennsylvania, Early Cambrian
ramp deposition was suc-
ceeded by deposition of platform-margin and periplatform
facies of the Kinzers Formation.
The basal Sauk II transgression during the early Middle
Cambrian submerged the plat-
form and reinitiated the peritidal cyclicity that had
characterized the pre-Hawke Bay depo-
sition. This thick stack of meter-scale cycles is preserved as the
Pleasant Hill and Warrior
Formations of the Nittany arch, the Elbrook Formation of the
Great Valley, and the Zooks
Corner Formation of the Conestoga Valley. Deposition of
peritidal cycles was interrupted
during deposition of the Glossopleura and Bathyriscus-Elrathina
Biozones by third-order deep-
ening episodes that submerged the platform with subtidal facies.
Regressive facies of the Sauk
383
Brezinski, David K., John F. Taylor, and John E. Repetski,
2012, Sequential
development of platform to off-platform facies of the great
American

carbonate bank in the central Appalachians, in J. R. Derby, R.
D. Fritz,
S. A. Longacre, W. A. Morgan, and C. A. Sternbach, eds., The
great American
carbonate bank: The geology and economic resources of the
Cambrian–
Ordovician Sauk megasequence of Laurentia: AAPG Memoir 98,
p. 383 –420.
Copyright n2012 by The American Association of Petroleum
Geologists.
DOI:10.1306/13331500M983500
128.59.222.107 on Mar 24, 2017, 4:43 PM.
II supersequence produced platform-wide restrictions and the
deposition of the lower sandy
member of the Gatesburg Formation, the Big Spring Station
Member of the Conococheague
Formation, and the Snitz Creek Formation. Resubmergence of
the platform was initiated
during the late Steptoean (Elvinia Zone) with the expansion of
extensive subtidal thrombolitic
boundstone facies. Vertical stacking of no fewer than four of
these thrombolite-dominated
intervals records third-order deepening episodes separated by

intervening shallowing episodes
that produced peritidal ribbony and laminated mudcracked
dolostone.
The maximum deepening of the Sauk III transgression produced
the Stonehenge For-
mation in two separate and distinct third-order submergences.
Circulation restriction during
the Sauk III regression produced a thick stack of meter-scale
cycles of the Rockdale Run
Formation (northern Virginia to southern Pennsylvania), the
upper Nittany Dolomite, the
Epler Formation, and the lower Bellefonte Dolomite of the
Nittany arch (central Pennsyl-
vania). This regressive phase was interrupted by a third-order
deepening event that produced
the oolitic member of the lower Rockdale Run and the
Woodsboro Member of the Grove
Formation in the Frederick Valley. Restricted circulation
continued into the Whiterockian,
with deposition of the upper Rockdale Run and the Pinesburg
Station Dolomite in the Great
Valley and the middle and upper parts of the Bellefonte
Dolomite in the Nittany Arch region.
This deposition was continuous from the Ibexian into the
Whiterockian; the succession lacks
significant unconformities and there are no missing biozones
through this interval, the top of
which marks the end of the Sauk megasequence.
During deposition of the Tippecanoe megasequence, the
peritidal shelf cycles were
reestablished during deposition of the St. Paul Group. The
vertical stacking of lithologies in the
Row Park and New Market Limestones represents transgressive
and regressive facies of a

third-order deepening event. This submergence reached its
maximum deepening within the
lower Row Park Limestone and extended into the Nittany arch
region with deposition of the
equivalent Loysburg Formation. Shallow tidal-flat deposits were
bordered to the south and east
by deep-water ramp deposits of the Lincolnshire Formation. The
St. Paul Group is succeeded
upsection by ramp facies of the Chambersburg and the Edinburg
Formations in the Great
Valley, whereas shallow-shelf sedimentation continued in the
Nittany arch area with the
deposition of the Hatter Limestone and the Snyder and Linden
Hall Formations. Carbonate
deposition on the great American carbonate bank was brought to
an end when it was buried
beneath clastic flysch deposits of the Martinsburg Formation.
Foundering of the bank was
diachronous, as the flysch sediments prograded from east to
west.
INTRODUCTION
The outcrop belts that expose Cambrian and Ordovi-
cian strata in the central Appalachians (Figure 1) pro-
vide an excellent opportunity to examine the transition
from platform to off-platform facies of the great Amer-
ican carbonate bank (GACB) of Ginsburg (1982). Plat-
form facies are exposed in the Nittany arch region of
central Pennsylvania and the Great Valley, which
stretches from northern Virginia (Shenandoah Valley)
northeastward to eastern Pennsylvania (Lebanon Val-
ley) and adjacent New Jersey (Paulinskill Valley). Rapid
subsidence in the Pennsylvania depocenter (Read, 1989a,
b) resulted in the accumulation of more than 4000 m
(>13,120 ft) of carbonate-dominated strata in these out-

crop belts. Comparably thick wedges of periplatform
stratathataccumulatedincontinentalslopeandcontinen-
tal rise environments are preserved in the western parts
of the Conestoga Valley of Pennsylvania and the Fred-
erick Valley of Maryland (Figure 1). In the easternmost
exposures of these valleys, much of the sequence is con-
densed into comparatively thin packages of black shale
and shaly limestone that were deposited in sediment-
starved basinal environments.
The goal of this chapter is to summarize the results
of research conducted during the last two decades on
the history of sea level change and derivative sequence
stratigraphy and cyclostratigraphy in the deposits of
the GACB in the central Appalachian region (i.e., the
Pennsylvania depocenter of Read, 1989a, b). We have
continued to subdivide this immense stack of Cam-
brian and Ordovician platform and periplatform carbon-
ates on an increasingly finer scale through an integrated
approach best described as a biostratigraphically con-
strained event stratigraphy. Recently recovered trilobite
and conodont faunas from all of the outcrop belts have
384 Brezinski et al.
128.59.222.107 on Mar 24, 2017, 4:43 PM.
expedited recognition and correlation of numerous
third-order (grand cycle-scale) transgressive-regressive
cycles across the entire platform. Some of these third-

order events also affected the style of deposition in
off-platform environments and/or in other shallow-
marine depositional basins, facilitating correlation into
coeval successions in other regions. In many poorly
studied regions, however, the biostratigraphic control
is sparse and the correlations are offered only as hypoth-
eses to be tested as new information becomes available.
The numerical orders of cycles and sequences used
in this chapter are intended only as categories of con-
venience (see Schlager, 2004) based entirely on scale
(thickness and implied duration), with no implication
of a specific forcing mechanism or presumption of eu-
static origin. Many of the third-order sequence bound-
aries are mappable because of the contrast in the un-
derlying and overlying lithofacies, typical of flooding
surfaces and unconformities. Consequently, many of
these horizons have been used as formation or member
boundaries to produce more highly refined lithostra-
tigraphy both for surface mapping and for correlation
in the subsurface. Many of the figures provided here
are updated cross sections that show the distribution of
lithofacies and correlation of the sequences that they
define. Most depict the distribution of sequences de-
lineated in the Sauk megasequence, from which most
of our new information were collected. A brief and more
tentative treatment of the cycle and sequence stratig-
raphy of the Middle Ordovician (Tippecanoe megase-
quence) carbonates is provided at the end of the chapter
to carry the history of the GACB through to completion
with its destruction during Taconic orogenesis.
THE SAUK MEGASEQUENCE
As in other areas of Laurentian North America, the

carbonates deposited on and adjacent to the GACB in
the central Appalachians constitute much of the Sauk
and Tippecanoe sequences of Sloss (1963). In recent
studies (Golonka and Kiessling, 2002; Miller et al., 2004),
these large-scale first-order sequences or cycles are re-
ferred to as megasequences. Palmer (1981) demonstrated
that the Sauk megasequence is divisible into three sub-
sequences (now supersequences) that he termed Sauk I,
Sauk II, and Sauk III, in ascending order (Figure 2). We
interpret each of these Sauk supersequences as
second-order transgressive-regressive cycles. Read
(1989) further subdivided Sauk I and Sauk III into two
parts, thereby delineating five transgressive-regressive
cycles or sequences within the Sauk megasequence
Figure 1. Outcrop belts (shaded) and
specific areas of exposure (white lettering)
of Cambrian and Ordovician strata of the
great American carbonate bank in the
central Appalachians. 50 km (31 mi).
Sequential Development of Platform to Off-platform Facies 385
128.59.222.107 on Mar 24, 2017, 4:43 PM.
in this region. The basal sequence (sequence 1) of Read
(1989), termed the preplatform shelf, is composed of
siliciclastic deposits that accumulated in rift-to-drift
shelf and basinal environments on the southern margin
of Laurentia before initiation of carbonate deposition
during passive margin creation. Hence, the oldest car-

bonate strata at the base of sequence 2 (in the middle of
the Sauk I supersequence of Palmer, 1981) record the
birth of the GACB in the central Appalachians (Cecil
et al., 2004).
Sauk I Ramp to Shelf Facies Transition
Recent detailed studies of the Cambrian stratigraphy
of the eastern Great Valley in Maryland (Brezinski, 1992)
and the Conestoga Valley in southeastern Pennsylva-
nia (Taylor and Durika, 1990; Taylor et al., 1997) sup-
port and clarify the major elements of the depositional
history in the Early Cambrian reconstructed by Read
(1989a) for this region. They bear out the initial devel-
opment of a carbonate ramp, followed by evolution of
the margin into a high-relief shelf with widespread
shale deposition landward of a narrow rim of microbial
reefs and ooid shoals. However, new biostratigraphic
data, in conjunction with a refined member-level litho-
stratigraphy, reveal inaccuracies in some previous inter-
pretations and miscorrelation of some units within Pen-
nsylvania and Maryland. Detailed mapping facilitated
by subdivision of the Tomstown Formation into four
members in the Great Valley (Brezinski, 1992) resulted in
the discovery of complex structures that had been
overlooked in previous studies (Figure 3). The lowest
Tomstown strata are made up of finely laminated
marble within the basal Bolivar Heights Member
Figure 2. The correlation of
groups and formations in the
Sauk and Tippecanoe megase-
quences in the central Appala-
chians. Dol = Dolomite; Fm =
Formation; Gp = Group.

128.59.222.107 on Mar 24, 2017, 4:43 PM.
(Figure 4A). This marble is traceable along the western
margin of the Blue Ridge from Pennsylvania to Vir-
ginia. This unit, named the Keedysville marble bed, is a
mylonite that marks a detachment zone along which
the entire Cambrian and Ordovician carbonate stack
appears to have been decoupled from the underlying
ChilhoweeGroupclasticsduring later Paleozoic orogen-
esis (Brezinski, 1992; Brezinski et al., 1996; Campbell
and Anderson, 1996). Jonas and Stose (1930, 1944) de-
scribed what appears tobe an analogous tectonitewithin
the correlative lower Vintage Formation of the Conestoga
Valley.
Some formation contacts in or near this detachment
zone that had been interpreted as depositional in na-
ture (Reinhardt and Wall, 1975; Read, 1989a) are now
known to have resulted from juxtaposition of units
by faulting. This is significant because cyclic peritidal
carbonates reported from the base of the Tomstown
Formation by Reinhardt and Wall (1975) led Read
(1989) to conclude that shallow peritidal deposition
was initiated very early in the deposition of sequence 2
in Maryland, in contrast to more protracted deposi-
tion of deep subtidal ramp facies at the base of this
sequence in Virginia. The discovery that the cyclic fa-
cies directly overlying the Chilhowee clastics in Mary-

land represents the highest member (Dargan Member)
of the Tomstown Formation, emplaced along a fault
nappe (Brezinski, 1992), eliminates the evidence for a
contrast in depositional conditions between Maryland
and Virginia, as well as the interpreted facies replace-
ment of nearshore clastics (Antietam Formation) by
peritidal cycles without an intervening phase of sub-
tidal ramp deposition in Maryland. In fact, where non-
deformed, the Bolivar Heights and Fort Duncan Mem-
bers of the Tomstown Formation in Maryland consist
mostly of burrow-mottled, noncyclic, subtidal ramp car-
bonates similar to those in the lower part of the Sauk I
supersequence (sequence 2 of Read, 1989) in Virginia
(Patterson Creek and Austinville Members of the Shady
Dolomite) and Pennsylvania (Vintage Formation). The
mottled fabric of the Bolivar Heights Member is un-
questionably the product of bioturbation (Figure 4B);
the origin of fabrics in the dolomite of the overlying
Fort Duncan Member is less certain. At least some parts
of the Fort Duncan Member display relict fabrics that
resemble stromatactoids and fenestrate thrombolitic
boundstone (Figure 4C). This suggests that the Fort
Duncan Member records the early stages of develop-
ment of the microbial reefs that eventually created a
narrow carbonate rim at the seaward margin of the
Figure 3. Lateral variations of lithologies and facies and
members of the Tomstown Formation along depositional strike
in the
eastern Great Valley from Virginia to southern Pennsylvania,
with derivative relative sea level curve. 10 m (33 ft); 1 km (0.6
mi).

128.59.222.107 on Mar 24, 2017, 4:43 PM.
shale-dominated shelf during deposition of the upper-
most part of Sauk I. The light-colored dolomite of the
overlying Benevola Member (Figure 4D) strongly re-
sembles the Ledger Formation in southeastern Penn-
sylvania and the Austinville Member of the Shady
Dolomite of Virginia, which accumulated in ooid sand
shoals at the very edge of the shelf (Figure 3). Both the
Benevola Member and lower Ledger display some relict
cross-stratification and are quarried extensively because
of their exceptional purity. As previously noted, the
overlying Dargan Member is characterized by well-
developed meter-scale peritidal cycles (Figure 4E)
similar to those that are ubiquitous in the Middle and
Upper Cambrian units in this region. It is likely that
the cycles of the Dargan Member formed through pe-
riodic shoreward progradation of broad outer-shelf
banks similar to those that produced its slightly youn-
ger counterparts (Figure 3).
A slightly different style of deposition prevailed on
the outer shelf in the latest Early Cambrian when the
pure carbonate belt shrank to form a narrow rim only
10 to 15 km (6.2–9.3 mi) wide during deposition of the
Figure 4. The Sauk I ramp and
platform lithologies. (A) The
laminated tectonite Keedysville
marble bed at the base of the

Tomstown Formation. (B) The
typical burrow-mottled limestone
of the of the Bolivar Heights
Member ramp facies of the Toms-
town Formation. (C) The clotted
microbial fabric of the Fort Duncan
Member of the Tomstown Forma-
tion. (D) The massive, fractured,
light-gray dolomitized sand shoal
facies of the Benevola Member of
the Tomstown Formation. (E) The
meter-scale limestone-dolomite
cycles (arrows) within the Dargan
Member of the Tomstown For-
mation. (F) The shaly limestone-
dolomite cycles of the Red Run
Member of the Waynesboro For-
mation. (G) The massive dolo-
mitized mud biostrome of the
upper Cavetown Member of
the Waynesboro Formation.
(H) The transition from subtidal
limestone to peritidal cycles at
the contact between the Cavetown
(Cwak) and Chewsville (Cwac)
Members of the Waynesboro
Formation.
128.59.222.107 on Mar 24, 2017, 4:43 PM.

shale-rich Waynesboro Formation (Read, 1989a). The
Waynesboro Formation is a succession of siliciclastic-
rich carbonate strata that was subdivided into three
members in the eastern Great Valley by Brezinski (1992):
the Red Run, Cavetown, and Chewsville Members, in
ascending order (Figure 5). The basal and upper mem-
bers (Red Run and Chewsville) are dominated by peri-
tidal cycles that consist of carbonates interbedded
with red and green siliciclastics. A typical mixed clastic-
carbonate meter-scale cycle comprises reddish to light-
gray Skolithos-bearing sandstone that grades upward
into tan laminated dolomite and red-brown mudcracked
siltstone and shale. The intervening Cavetown Mem-
ber lacks the clastic components of the other members.
This middle member contains massive dolomitic lime
mudstone, in packages as much as 20 m (66 ft) thick at
the base and near the top of the unit. The remainder of
the member consists of peritidal cycles in which gray,
thick-bedded, burrow-mottled dolomitic limestones
grade upward into tan, laminated, mudcracked dolo-
mites (Figure 5).
Within the Great Valley, Lower Cambrianstrata of the
Waynesboro Formation (Bonnia-Olenellus Biozone) are
directly overlain by middle Middle Cambrian (Glosso-
pleura Zone) strata of the Elbrook Formation (Brezinski,
1996a). The absence of the Poliella and Albertella Zones is
attributable to the Hawke Bay event (Palmer and James,
1979), a major craton-wide regressive episode that re-
sulted in a sizable unconformity between Sauk I and
Sauk II in all but the most rapidly subsiding depo-
centers (Palmer, 1981) (Figure 5).
Within the Nittany arch of central Pennsylvania,
only thin slices of the Lower Cambrian section are ex-

posed in the hanging walls of several large thrust faults.
The red siltstones and shales resembling the Chews-
ville Member of the Waynesboro Formation exposed in
that area are the only Lower Cambrian strata exposed
west of the Great Valley in the central Appalachian
transect.
Sauk I Platform-margin and Off-platform Facies
Although some uncertainty remains regarding a shelf-
break origin for the members of the Tomstown For-
mation, the formations in the upper part of Sauk I and
at the base of Sauk II in the Conestoga Valley undoubt-
edly represent shelf-marginal and off-platform envi-
ronments (Rodgers, 1968; Gohn, 1976; Reinhardt, 1977;
Taylor and Durika, 1990; Taylor et al., 1996; De Wet
et al., 2004). Figure 6 shows the lithostratigraphic and
biostratigraphic units recognized in the Lower and Mid-
dle Cambrian of the eastern Great Valley and Conestoga
Valley, along with the biozones established for this in-
terval. Figure 7 illustrates the lateral facies relationships
between the carbonate-rich units of the eastern Great
Valley and the periplatform and off-platform facies of the
Conestoga Valley.
The Vintage Formation, which directly overlies the
Chilhowee clastics in the Conestoga Valley, consists
of burrow-mottled carbonates similar to those within
the Bolivar Heights and Fort Duncan Members of the
TomstownFormation(Figure8A).Likethelowermembers
Figure 5. The stratigraphic column of the Waynesboro
Formation with relative sea level curve based on stacking
of lithologic components. The amplitude and frequency
of fourth-order and smaller cycles were approximately

portrayed. 50 m (164 ft).
128.59.222.107 on Mar 24, 2017, 4:43 PM.
of the Tomstown Formation, the Vintage Formation ap-
parently formed through deposition on a subtidal ramp.
The overlying Kinzers Formation, which has no counter-
part in the Great Valley succession, has been interpreted
as a wedge of periplatform sediment that accumu-
lated in slope-to-rise environments (Gohn, 1976;
Taylor and Durika, 1990), seaward of the shelf-margin
ooid shoals on which the pure dolomite of the
overlying Ledger Formation was deposited. Marked
changes in lithofacies and profound thickening of the
Kinzers Formation from the eastern to western Cones-
toga Valley indicate that the platform had evolved into
a high-relief constructional rimmed shelf by the time of
Kinzers deposition. In the eastern Conestoga Valley, the
entire Kinzers is approximately 70 m (~230 ft) thick
and comprises a lower member dominated by dark-
gray shale (Emigsville Member) (Figure 8B), an un-
named middle member consisting of bluish …

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