ABSTRACT
The coastal cliffs along the eastern shore of Chignecto Bay, Nova
Scotia contain one of the finest Carboniferous sections in the world. In
1843, Sir William Logan measured the entire section as the first project
of the Geological Survey of Canada, and defined eight stratigraphic
divisions. We have re-measured a section corresponding almost exactly
with Logan's Division 5 in bed-by-bed detail. The strata are
exposed in the wave-cut platform and low-relief bluffs of a 2 km-long
section at Lower Cove, near Joggins, north and south of Little River.
This 635.8 metre-thick succession until now has been included within the
basal part of the Joggins Formation, and overlies the Boss Point
Formation. However, the studied strata are lithologically distinct, and
are formally recognized as the new Little River Formation. This
formation is bounded by regionally important surfaces and is traceable
inland for 30 kilometres from its Lower Cove type section. Facies
analysis indicates that it represents the deposits of a well-drained
alluvial plain dissected by shallow rivers characterized by flashy flow.
It can be clearly distinguished from the underlying Boss Point Formation
(Logan's Division 6) by its much smaller channels, and from the
overlying Joggins Formation (Logan's Division 4) by lack of coal
seams and bivalve-bearing limestone beds. Palynological assemblages
indicate that the Little River Formation is of probable late Namurian to
basal Westphalian (basal Langsettian) age, and is a likely
time-equivalent of the informal Grand-Anse formation of southeast New
Brunswick.
RESUME
Les falaises cotieres longeant le rivage oriental de la baie
Chignectou, en Nouvelle-ecosse, abritent l'un des stratotypes
carboniferes les plus interessants dans le monde. Sir William Logan
avait mesure en 1843 l'ensemble du stratotype dans le cadre du
premier projet de la Commission geologique du Canada et il avait defini
huit divisions stratigraphiques. Nous avons mesure a nouveau un
stratotype correspondant presque exactement dans ses details couche par
couche a la division 5 de Logan. Les strates affleurent dans une
plate-forme d'erosion et des falaises de reliefemousse d'un
secteur de deux kilometres de longueur a l'anse Lower, pres de
Joggins, au nord et au sud de la riviere Little. Cette succession de
635,8 metres d'epaisseur avait jusqu'a maintenant ete incluse
a l'interieur de la partie basale de la Formation de Joggins et
elle recouvre la Formation de Boss Point. Les strates etudiees sont
cependant lithologiquement distinctes et on les reconnait officiellement
en tant que nouvelle Formation de Little River. Cette formation est
limitee par des surfaces importantes a l'echelle regionale; on peut
la retracer a l'interieur des terres sur 30 kilometres a partir de
son stratotype de l'anse Lower. Une analyse du facies revele
qu'il represente les depots d'une plaine alluviale bien
drainee, sectionnee par des rivieres peu profondes caracterisees par des
crues eclair. On peut nettement la distinguer de la Formation
sous-jacente dc Boss Point (division 6 de Logan), grace a ses canaux
beaucoup plus petits, ainsi que de la Formation sus-jacente de Joggins
(division 4 de Logan), par l'absence de couches houilleres et de
couches de calcaire abritant des lamellibranches. Les assemblages
palynologiques revelent que la Formation de Little River remonte
probablement a la periode du Namurien tardif au Westphalien basal
(Langsettien basal) et qu'elle constitue vraisemblablement un
equivalent chronologique de la Formation officieuse de Grande-Anse dans
le sud-est du Nouveau-Brunswick.
[Traduit par la redaction]
INTRODUCTION
The cliffs along the eastern shore of Chignecto Bay, Nova Scotia
(Fig. 1), have been long considered one of the world's classic
Carboniferous sections (Lyell 1871; Gibling 1987). The seminal work that
defined the stratigraphy of these cliffs was that of Sir William Logan,
who undertook bed-by-bed measurement of the section as the first project
of the Geological Survey of Canada (Logan 1845; Rygel and Shipley 2005).
In this paper, we examine in detail for the first time since that work
the section of low topographic relief between the Boss Point Formation,
with its prominent, thick sandstone bodies that were a valued source of
grindstones in the Nineteenth Century, and the cliff section of the
Joggins coal measures. These coal-bearing strata provided Sir William
Dawson and Sir Charles Lyell their seminal paleontological discoveries
in the mid-Nineteenth Century (Falcon-Lang and Calder 2004).
[FIGURE 1 OMITTED]
The strata described herein are exposed in the wave-cut platform
and bluffs in the 2 km-long red bed section at Lower Cove, near Joggins,
north and south of Little River, near the village of Lower Cove. This
stratal interval, 636 m thick, almost exactly corresponds with Division
5 of Logan (1845). Our newly measured section log (Appendix A), recorded
in the field at 1:100, and digitally transcribed by Andrew Henry,
adjoins a similar log of the overlying Joggins Formation undertaken
concurrently by Sarah Davies and Martin Gibling (see Davies et al.
2005). Together, these papers provide a continuous reference log of the
Joggins section from South Reef at the upper contact of the Boss Point
Formation to the contact of the Joggins Formation with the overlying
Springhill Mines Formation, north of MacCarrons Creek. Together, the two
papers thus incorporate the first comprehensive log of the classic
Joggins section to have been completed since that of Logan (1845).
The section of red beds described in this paper provides a clear
basis for the division and redefinition of stratigraphic units, in
particular the relationship of the Boss Point and Joggins formations
with coeval units exposed across Chignecto Bay in New Brunswick.
Furthermore, the Lower Cove red beds are key to understanding the
evolution of the coeval landscape, setting the stage for the environment
recorded in the overlying Joggins Formation.
GEOLOGIC SETTING
The western Cumberland Basin, now represented by the Athol
Syncline, was an active depocentre within the broader Maritimes Basin
during Carboniferous time. At this time, the basin was then positioned
close to the equator, east of the rising Appalachian mountains and
midway between the Appalachian and western European foreland basin
complexes (Calder 1998). Highland massifs bordered the Cumberland Basin
to the south (Cobequid Highlands) and west (Caledonia Highlands) (Fig.
1). The western part of the basin, in which the Lower Cove section
occurs, experienced subsidence rates unsurpassed in coeval coal basins
of Europe and North America (Calder 1994; Davies and Gibling 2003).
Contributing to this subsidence history was the halokinetic withdrawal
of thick Mississippian salt deposits (Waldron and Rygel 2005). The age
of coastal exposures of the Carboniferous basin-fill on the western
coast of Chignecto Bay spans the Visean through early Westphalian
(Duckmantian) interval.
Stratigraphic History
The first stratigraphic account of the Carboniferous section at
Joggins, and for the Maritimes Basin in general, was the pioneering work
of Brown and Smith (1829). Their stratigraphic framework, and subsequent
modifications (Fig. 2; Gesner 1836, 1843; Lyell 1843; Dawson 1878),
underscore the geologic parallels between once-contiguous Nova Scotia
and British Isles (Calder 1998).
[FIGURE 2 OMITTED]
The Carboniferous strata exposed along the eastern shore of
Chignecto Bay were first measured by William Logan during the summer of
1843 (Logan 1845; reprinted in Poole 1908). Logan measured about 15 km
of virtually continuous coastal section from Minudie south to Shulie, a
succession that, by his calculation, totalled 4442.4 m (14 570 feet, 11
inches). Incredibly, this feat was achieved during a five-day stop en
route from London to the Gaspe Peninsula (Rygel and Shipley 2005) as he
began the search for coal-bearing strata in Lower Canada; it constituted
the first field project of the fledgling Geological Survey of Canada.
Logan subdivided his section into eight lithologically distinct
divisions, numbered from youngest (1) to oldest (8). The red beds of
Lower Cove were assigned to Division 5, and the overlying coal measures
of the Joggins and Springhill Mines formations to Divisions 4 and 3
respectively. The sandstone-dominated strata of the underlying Boss
Point Formation were assigned to Division 6. Logan placed the lower
contact of Division 5 at the top of "South Reef" (Fig. 3),
which we consider to represent the uppermost sandstone body of the Boss
Point Formation. He placed the upper contact 5 ft, 6 in (1.65 m) below
the stratigraphically lowest coal (no. 45) of Division 4, a bed that we
propose herein as the basal datum of the revised Joggins Formation (see
below).
[FIGURE 3 OMITTED]
Logan's "Recapitulation" of Division 5 reads as
follows: "dominated by red shale, reddish grey sandstone with
occasional "drift plants" and "concretionary
limestone", and minor greenish grey sandstone, totally 2082 ft 0
in". The thickness of the Lower Cove red beds (634.6 m) obtained by
Logan agrees remarkably closely with the thickness of 635.8 m measured
in this study (a mere 1.26 m difference). Despite minor modifications
and combinations over the years, Logan's (1845) measurements and
subdivisions form the basis for all later stratigraphic studies of the
Carboniferous basin fill of the Cumberland Basin.
Relationship to other units within the Cumberland Basin
The stratigraphic relationship of the Lower Cove red beds to other
units within the Basin (other than those in direct contact in the
coastal exposures) has long been enigmatic. Brown and Smith (1829) did
not distinguish the Lower Cove beds from their "Millstone
Grit" and overlying "Coal Measures" (Fig. 2). Dawson
(1855) originally assigned Divisions 5-8 to the "Lower or Older
Coal-Formation", broadly analogous to the Lower Carboniferous, but
later reconsidered and correlated these strata with the
"Millstone-grit Series" (Dawson 1868). Grouping of
Logan's Divisions into more broadly recognized lithostratigraphic
units represented an attempt to correlate these stratal packages beyond
the confines of the basin, but required an understanding of local
sedimentation patterns within the tectonically active Cumberland Basin.
During the first half of the Twentieth Century, Bell (1912, 1914,
1927, 1938, 1944, 1958) studied the paleontology and regional
stratigraphy of the Carboniferous of Nova Scotia. Well aware of the
lithostratigraphic complexities of the Cumberland Basin, Bell felt that
the basin fill could be more naturally subdivided on the basis of
unconformities as indicated by the floral and faunal record. Bell's
regional stratigraphy, grounded in his steadfast belief in
unconformity-bound groups, became the definitive work of the Twentieth
Century, but his combined use of bio- and lithostratigraphic definitions
proved impractical. Influential advocates of a purely lithostratigraphic
approach to the regional stratigraphy of the Maritimes Basin have been
Belt (1964, 1965) and Kelley (1967), and their viewpoint was followed,
at least in part, by Ryan et al. (1991).
In his first round of stratigraphic revisions, Bell (1912, 1914,
1938) grouped Logan's Divisions 3-5 and basal Division 2 into his
"Joggins Formation". His grouping of the Lower Cove red beds
(Division 5) with the overlying coal-bearing strata (Division 3-4) was
based, in part, on the lack of contrary (or indeed any) macrofloral
evidence within the red beds. Bell (1914, 1927) correlated the contact
between coal-bearing strata and conglomerate at Spicer's Cove (Fig.
1) on the south limb of the Athol Syncline (Fletcher 1908) with the
contact between Divisions 5 and 6 at Lower Cove. This correlation, later
shown to be incorrect by Ryan et al. (1990a, 1990b), contributed to the
impracticality of mapping his Shulie and Joggins formations inland (see
map notes of Bell 1938). Consequently, Bell (1938) later advocated for
an undivided Cumberland Series, later still, Bell (1944, 1958) defined
the Cumberland Group, comprising Divisions 1-5, and the Riversdale
Group, comprising Divisions 6-7.
In the mid Twentieth Century, efforts were renewed to map the basin
file Central to this work was the goal of establishing stratigraphic
relationships between the coastal section and the economically important
coal measures of Springhill. In the course of this work, Shaw (1951)
recognized the red beds of Lower Cove as a lithologically distinct
subunit (10a) of his "coal-bearing facies" and considered the
red beds to be coeval with basin-margin conglomerates (his map unit 9,
the Polly Brook Formation of later authors) near Springhill (Fig. 1).
Copeland (1959) concurred, but grouped the Lower Cove red beds with the
basin-margin conglomerates (his "Facies A").
On the strength of their interpretation that the coal-bearing
strata of Spicer's Cove were correlative with the Joggins coals and
were underlain by conglomerates exposed at the south of Spicer's
Cove, Bell, Shaw and Copeland correlated the Lower Cove red beds with
basin margin conglomerates. Palynostratigraphic studies (Hacquebard and
Donaldson 1964; Dolby 1991) have demonstrated, however, that the
Spicer's Cove section is younger than that of Lower Cove, a
conclusion supported by the macrofloral record (R.H. Wagner, personal
communication, 2000). A growing body of evidence further suggested that
the contact between the Lower Cove red beds and the underlying Boss
Point Formation was likely conformable (Hacquebard 1972; Howie and Barss
1975).
Later in the century, a subsequent round of mapping and
stratigraphic investigations in the Cumberland Basin was undertaken by
the Nova Scotia Department of Natural Resources (Ryan et al. 1990a,b,c,
1991; Calder 1995). The lithostratigraphic distinctiveness and
regionally mappable boundaries of the Lower Cove red beds were
acknowledged by Ryan et al. (1990a) on their geological map, but this
unit was nonetheless included with the coal-bearing strata of Division 4
and the basal 51 m of Division 3 in their revised and reinstated Joggins
Formation (Ryan et al. 1991). Members were not formally defined within
this 1433 m-thick unit, although the informal term "Little River
Bridge member" was used by Ryan et al. (1991, their fig. 5) and
Ryan and Boehner (1994, their figs. 2-13) in reference to the Lower Cove
red beds.
[FIGURES 4-13 OMITTED]
LITTLE RIVER FORMATION
Definition
Here we formally propose the elevation of the Lower Cove red beds
to the status of formation, and coin the name Little River Formation for
these beds. Our proposed unit is defined purely on the basis of
lithostratigraphy, being a non-coal-bearing, red-bed succession
positioned conformably above the Boss Point Formation and conformably
beneath the coal-bearing strata of the Joggins Formation. The formation
is named after Little River, the mouth of which crosses the type section
where it enters Chignecto Bay at Lower Cove. For the sake of clarity, it
is important to note that this newly proposed unit bears no relationship
to the now historically obsolete "Little River Group" of
southern New Brunswick (Dawson 1868, p. 506), despite these strata being
approximately time-equivalent. These strata are now assigned to the
Lancaster Formation of Alcock (1938), and include the classic "Fern
Ledges" of Stopes (1914).
Justification
The Little River Formation comprises a lithologically distinctive
and regionally mappable unit. It lacks both coal and bivalve-bearing
limestone beds, the two defining hallmarks of the overlying Joggins
Formation (Ryan et al. 1991). It is also lithologically distinct from
the underlying Boss Point Formation, which is characterized by thick,
multistorey, well sorted grey sandstones, features absent from the
Little River Formation. Similarly, although it is considered to be, in
part, coeval with the Polly Brook Formation, it is lithologically
distinct from that polymictic conglomerate succession. Both the base and
top of the Little River Formation are regionally important surfaces.
Type locality
The type section comprises outcrops in the intertidal zone and
low-relief coastal bluffs on the eastern shore of Chignecto Bay, at
Lower Cove, near Joggins, Cumberland County, Nova Scotia (Fig. 3). The
section begins at the top (southern edge) of the South Reef of the Boss
Point Formation (UTM Coordinates 5066450N, 388000E; NAD 83 datum) and
extends 1500 m southward to a point 500 m south of the mouth of Little
River (5063200N, 388400E). The top of the section coincides with the
base of the lowest coal bed (Coal 45 of Logan 1845) of the Joggins
Formation, near the start of the continuous cliff section.
Reference localities
Strata of the Little River Formation are known to occur inland on
four stream sections east of the type section (Fig. 1; and see Ryan et
al. 1990a). These include, from west to east: 1) exposures on a small
tributary to the Maccan River north of the village of Maccan; 2) along
Baird Brook at Chignecto; 3) near the contact with the Polly Brook
Formation on Saint George's Brook east of Chignecto, which at this
locality underlies the Little River Formation; and 4) on Styles Brook
south of Stanley.
Boundaries
The basal contact of the Little River Formation is placed at the
top of the highest multistorey sandstone bed of the Boss Point
Formation, which at the type section is the top of the South Reef,
coinciding with the base of Division 5 of Logan (1845). Inland, to the
east, the base of the formation progressively onlaps against polymictic
conglomerates of the Polly Brook Formation (Ryan et al. 1990a). The
upper contact of the formation is placed at the base of the
stratigraphically lowest coal bed, which at the type section is coal 45
of Logan (1845), 1.65m above the base of Logan's Division 4. This
upper contact defines the base of the revised Joggins Formation (see
Davies et al. 2005). The onset of grey mudrock and sandstone in the
Joggins Formation provides a secondary criterion in mapping incompletely
exposed sections. The formation has been mapped by the first author
inland from the type section, its boundaries indicated on the map of
Ryan et al. (1990a), where the formation, then unnamed, was designated
"abundant redbeds"
Thickness and distribution
The type section at Lower Cove, constituting a remeasurement of
Division 5 of Logan (1845), is 635.8 m thick. The formation can be
traced 30 km to the east along the north limb of the Athol Syncline to
Styles Brook (Ryan et al. 1990a), where it eventually pinches out
between the underlying Polly Brook Formation and overlying Joggins and
Springhill Mines formations (Fig. 1). Because of many similarities, the
Lower Cove beds may be laterally equivalent to fault-bound strata
exposed across Chignecto Bay to the west on Maringouin Peninsula, New
Brunswick, assigned to the informal Grande Anse formation (St. Peter and
Johnson 1997), as well as to undesignated strata along strike of the
Grand Anse beds at Minudie Point.
Correlation
Inland, the Little River Formation is in part laterally
time-equivalent to coal-bearing strata of the Joggins Formation and is
inferred to be laterally equivalent to the Polly Brook Formation on the
south limb and in the east of the Athol Syncline (Figs. 1, 4). Although
it is probable that the Grande Anse formation in southeast New Brunswick
may represent a facies of the Little River Formation, the correlation of
the two units is problematic due to uncertainties in the stratigraphic
relationship of the Grande Anse formation with adjacent geologic units.
The lower contact of the Grand Anse section is in faulted contact with
the Boss Point Formation at the coast, although the contact is reported
to be conformable in the axis of the Hardledges Syncline south of the
Shepody-Beckwith Fault (Johnson 1996). At its upper contact, the Grand
Anse formation is in faulted contact with the Mississippian Windsor
Group. Johnson (1996) suggested correlation of the Grande Anse with the
Polly Brook Formation and lower Joggins (Little River of this paper)
Formation.
Age
Age determination of the Little River Formation is problematic due
to its sparse paleontological record and, in particular, the complete
absence of key age-diagnostic marine index fossils (Calder 1998; R.H.
Wagner, personal communication, 2004). Furthermore, although palynology
offers an alternative means to date strata, difficulties exist in
disentangling evolutionary signatures from paleoecological effects, with
these uncertainties in mind, comprehensive palynostratigraphic studies
of the type section place the Little River Formation within the upper
Namurian (Kinderscoutian) to basal Westphalian (basal Langsettian)
according to Dolby (1991, 2003), or entirely within the upper Namurian
(Marsdenian to Yeadonian) according to J. Utting (personal
communication, 2004). Extensive revision by R.H. Wagner of the
macroflora of the overlying Joggins Formation demonstrated a floral
assemblage consistent with the Langsettian of Europe, and Langsettian
floral elements are present along with problematic
"hinterland" taxa in the underlying Boss Point Formation
(Utting and Wagner 2005).
The miospore Cananoropolis mehtae until recently was known only
from strata in the informal "Coal Mine Point member" of the
Joggins Formation (Ryan et al. 1991), and was used therefore as local
index taxon. Its occurrence in red beds of the Grande Anse section on
Cape Maringouin, New Brunswick, was cited as evidence of a late
Langsettian age for these strata (Dolby 1999). Subsequent sampling of
the formation at Lower Cove, however, yielded a much earlier, albeit
solitary specimen of Cananoropolis mehtae (Dolby 2003), suggesting that
it may be less useful as a local index taxon than previously assumed,
and therefore giving cause to reconsider the late Langsettian age for
the Grande Anse formation. Its presence within the Lower Cove and Grande
Anse strata further suggests that the two formations are possible
correlatives.
SEDIMENTOLOGY OF THE LITTLE RIVER FORMATION
Major sandstone channel bodies
Twelve prominent (>2m-thick) channel bodies crop out on the wave
cut platform as prominent "reefs", and vary in width from
31-534 m. Channel bodies have been assigned numerical designations (Fig.
3) that correspond to the stratigraphic position in metres of the top of
their uppermost bed in the measured section. Channel bodies are
described using the bounding surface and lithofacies terminology of
Miall (1996). Smaller channel bodies (<2 m thick) also occur, but are
dealt with separately below.
Channel body geometry
The lateral exposure of Little River channel bodies varies
depending on their size and position on the shoreline. Five fully
exposed channel bodies are 2.4 to 6 m thick and have width:thickness
(W:T) ratios ranging between 6 and 43 when measured perpendicular to
paleoflow. Seven incompletely exposed channel bodies are 3.1 to 10 m
thick and have minimum W:T ratios of 13.6 to 147 when measured
perpendicular to paleoflow.
The architecture of these sandstone channel bodies is defined by
5th order (channel body-) bounding surfaces, which both separate there
from the underlying mudrocks and compartmentalize them into vertically
stacked, or abutting, storeys. The basal storey/storeys of many channel
bodies comprise(s) an obviously erosional 5th order surface, which forms
one or more concave-up channel bases. These U-shaped forms are 3.1 to 7
m thick with W:T ratios between 5 and 25. Where concave-up surfaces
flatten, they pass into the relatively bedding-parallel, 5th order
surface that defines the base of the overlying, more tabular storey.
These uppermost tabular storeys are 1 to 4 m thick with W:T ratios
greater than 35. The overlying storeys are similar to the thick
sandstone "wings" of Friend et al. (1979). In summary, the
composite sandstone channel bodies are amalgamations of U-shaped
erosional storeys and overlying, more laterally extensive storeys.
Internally, storeys contain numerous 3rd and 4th order bounding
surfaces (macroform growth increment and macroform bounding,
respectively) that separate the sandy fill into channel elements and
sandy bedforms. Individual channel elements are generally 1.5 to 6 m
thick and have a narrow, U-shape in cross-section (W:T ratio <10).
Inclined stratification within sandy bedforms is variably oriented with
dips ranging from perpendicular to oblique to the channel margin. Third
and fourth order surfaces divide the basal part of most storeys into
stacked packages of crudely stratified intraformational conglomerate
(Gh) overlain by trough, planar, or low-angle cross-bedded sandstone
(St, Sp and Sl, respectively). The upper portions of these channel
bodies, and the entirety of others (e.g. the channel body at 465 m),
contain varying proportions of horizontally, low-angle, and/or ripple
cross-laminated sandstone (Sh, Sl, and Sr respectively). These intervals
commonly contain 3rd order bounding surfaces, which are expressed as
either low angle or channel-element bounding erosional surfaces.
A shallow erosional scour atop the channel body at 96 m (see
Appendix A) contains an assemblage of lithofacies unique within the
Little River Formation. The 2.45 m-deep and 20 m-wide scour is incised
into a 3 m-thick package of trough to low angle cross-bedded sandstone
and intraformational conglomerate. The basal 0.70 m of the scour is
filled with two sets of planar cross-bedded sandstone that are overlain
by approximately 15 cm of horizontally laminated sandstone. A
"sigmoidal" erosional surface (Fig. 5) cuts down from the
channel margin, truncating these basal units. The erosion surface is
draped by a form-concordant, sigmoidal blanket of ripple cross-laminated
sandstone that gradually becomes flat lying and passes upward into a
sheet that extends beyond the margin of the scour and caps the entire
channel body.
Sediment composition
Channel bodies generally are composed of quartz- and
calcite-cemented, very fine- to medium-grained feldspathic arenites.
Sandstones additionally contain abundant sand-sized clay particles with
bright clay fabric, which may represent mud aggregates
(Gierlowski-Kordesch and Gibling 2002; Muller et al. 2004). Erosion
surfaces are lined locally with crudely stratified intraformational
conglomerate (Gh) containing medium-to coarse-grained sandstone (Ss),
which is either interspersed as a matrix or co-occurs within separate
lenses. Lag deposits are clast supported and contain pebble-sized rip-up
clasts of red and green mudstone with rare granule-sized quartz clasts
(channel body at 90 m). Locally abundant calcareous rip-up clasts are
composed of concentric layers of finely crystalline calcite developed
around a core of sparry calcite. Although no root tissue was observed,
these clasts are otherwise identical to the calcareous rhizoconcretions
described by Falcon-Lang et al. (2004) from red beds in the overlying
Joggins Formation.
Paleoflow
The orientation of trough cross-beds and ripples in the channel
bodies are plotted as rose diagrams (10[degrees] petals) on the measured
section (Appendix A) and outcrop map (Fig. 3). Planar cross-beds and
primary current lineations are locally abundant, but these structures
are relatively unreliable indicators of paleoflow, and omitted from
analysis. Measurements are grouped by structure type within individual
channel bodies to allow for comparison between different scales of
structures and for intrachannel variation. Because the orientation of
troughs and ripples are linear features, they need not be corrected for
the [less than or equal to] 25[degrees] regional dip at the Lower Cove
type section (Porter and Pettijohn 1977).
Where ripples and trough cross-beds are measurable within the same
channel body (n=3), their mean orientation varied by 1[degrees] to
19[degrees] (mean = 7.7[degrees]). Given this similarity, these
structures are treated as equally reliable and used to calculate a mean
paleoflow direction for each channel body (Fig. 3). The twelve Lower
Cove channel bodies showed a reasonably strong southwest trend (mean =
245[degrees], r = 0.6). Of the four bodies that deviate from this trend,
three exhibit paleoflow to the northwest with the remaining one to the
northeast. In comparison, trough cross-beds within Grand Anse strata at
Black Point and at Grande Anse, New Brunswick, record a NNE paleoflow
(Browne 1991).
Comparison with bracketing formations
Channel bodies of the Little River Formation are an order of
magnitude smaller than those of the underlying Boss Point Formation and
exhibit considerable differences in alluvial lithofacies and paleoflow
direction. Browne and Plint (1994) describe the Boss Point Formation as
being characterized by 20 to 90 m thick braidplain sandstone packages,
which are underlain by 6th order bounding surfaces and extend several
hundred metres across the intertidal zone. These bodies are composed
dominantly of trough cross-bedded sandstone and have individual channel
elements up to 35 m thick. Furthermore, the 245[degrees] (southwesterly)
trend of the Little River Formation channel bodies differs from the
southeasterly trend of the underlying Boss Point Formation by
70[degrees] (Browne and Plint 1994).
Little River Formation channel bodies also differ from those of the
overlying Joggins Formation in terms of both geometry and internal
architecture. Red beds in both formations contain channel bodies between
5 and 10 m thick, but examples in the Joggins Formation contain
significant amounts of interstratified mudrock, are contained within
small incised valleys, and are not capped by laterally extensive storeys
(Davies and Gibling 2003). Although some Joggins Formation channel
bodies (e.g., Coal Mine Point) are similar in size and geometry to those
in Lower Cove, these bodies are single storey and contain well developed
lateral accretion surfaces (Davies and Gibling 2003). Paleoflow within
the Little River and Joggins formations is variable, but large channel
bodies in both tend to have a southerly or southwesterly flow
orientation.
Mudrock-dominated intervals
Mudrocks
The Little River Formation is mudrock-rich, which contributes to
its low relief in the Lower Cove type section. Mudrocks, comprising
claystone to silty claystone, are predominantly red in colour.
Ubiquitous drab haloed root compressions are characteristic of the
formation; calcareous rhizoconcretions and amalgamated (dm-scale)
carbonate nodules occur locally. Discrete, thin (cm-scale), dark grey,
organic-rich mudrock intervals may occur at some horizons, and may
persist laterally for tens of metres, but true coal beds are absent.
Paleosols
Mudrocks within the Little River Formation contain three types of
paleosol, which are described here using standard terminology (Retallack
2001; Soil Survey Staff 2003). By far the most common type comprises
intervals containing drab haloed root compressions, locally associated
with standing vegetation. These weakly developed mineral paleosols lack
horizons and represent very weakly developed entisols. Their common
occurrence indicates pervasive pedogenesis throughout the accretion of
the Little River Formation. Smith (1991) studied similar, but better
developed paleosols in the overlying Joggins Formation and interpreted
them as paleo-alfisols formed under warm, oxidizing conditions. The
absence of pedogenic carbonate in the Joggins Formation paleosols
conflicts, however, with the interpretation of alfisols by DiMichele et
al. (in press) from Early Permian red beds of north-central Texas (see
below). Other paleosols in the Little River Formation exhibit surficial
horizons <10 cm thick that are composed of green or grey mudstone
with variable amounts of organic material and rooting. The most
organic-rich of these horizons consist of incipient histic epipedons
(surface horizons) capping weakly developed entisols.
A distinctive aspect of the paleosols of the Little River Formation
that contrasts with those of the Joggins Formation is the development of
calcic (Bk) horizons. These horizons contain discontinuous
carbonate-cemented nodules (<20 cm thick) that reach Machette's
(1985) Stage III of carbonate accumulation. Such pedogenic carbonate
development indicates xeric conditions and a semi-arid to arid climate
with seasonal drying and incomplete leaching (Soil Survey Staff 2003;
DiMichele et al. in press). Paleosols with vertically oriented
calcareous rhizoconcretions are similar to paleosols described from the
Early Permian of north-central Texas interpreted by DiMichele et al. (in
press) as alfisols; more extensively cemented pedogenic carbonate was
considered by these authors to be indicative of inceptisols. Clay
mineralogy and petrographic studies of the Little River paleosols at
Lower Cove will be required to refine these preliminary interpretations.
Small channel bodies
Small (<2 m thick), U-shaped (W:T <5) channel bodies occur
throughout the Little River Formation, hosted within the
mudrock-dominated intervals. These features have convex-down bases and
flat tops; mounded tops occur locally. Channel bodies commonly occur in
stacked groups where individual channel bodies are obliquely offset from
one another. Small channel bodies are either isolated within mudrock or
pass laterally into thin (<1 m thick) sheet sandstones. Channel fill
consists of varying proportions of horizontal, low-angle, and ripple
cross-laminated sandstone (Sh, Sl, and Sr respectively), or more rarely
may largely contain laminated, grey/green mudstone.
Sheet sandstone bodies
Thin (<1 m thick) sheet sandstones are commonly interbedded with
red mudrocks of the Little River Formation. These beds typically extend
for several tens of metres, their complete extent being unknown due to
limited exposure at Lower Cove type section. Internally, sheet
sandstones are often massive with localized areas of horizontal or
ripple cross-laminated sandstone (Sh and Sr, respectively). The presence
of drab haloed root compression and occasional calamitean plants in
growth position suggests that these beds experienced some pedogenic
overprinting. A few beds near the top of the section are very strongly
cemented by calcite, a phenomena that may reflect pedogenic accumulation
of calcite at or near the water table.
PALEONTOLOGY
In spite of 150 years of investigation of the rich terrestrial
fossil record of the Joggins section (Falcon-Lang and Calder 2004), no
floral or faunal records exist from the red beds of the Little River
Formation. The first records that have emerged in the course of this
study likely afford but a glimpse of the total biota of the Little River
ecosystem.
Fauna
Invertebrates
Aggregations of the land snail Dendropupa vetusta occur
concentrated on discrete drab horizons (98 m, Appendix A). These
aggregations represent surface litter accumulations (mode 2 occurrence
of Hebert and Calder 2004) that are consistent with the snail's
detritivorous autecology (Solem and Yochelson 1979). The Lower Cove
occurrences predate those of the Joggins Formation and so push back in
time the first appearance of pulmonate gastropods in the fossil record.
The presence of the largest known terrestrial detritivore, the
gargantuan millipede-like Arthropleura, is recorded by a 23 cm wide
Diplichnites trackway (Fig. 6; 335 m, Appendix A). The polychaete worm
Spirorbis is abundant in a single, small, grey mud-filled channel at 352
m in the measured section, where the epifauna densely adheres to drifted
cordaitalean trunks (see below).
Vertebrates
The solitary vertebrate record as yet obtained from the Little
River Formation is an occurrence at one horizon of large tetrapod
footprints (96.5 m, Appendix A) provisionally assigned to the ichnogenus
Pseudobradypus. The possible affinity of this ichnotaxon with the
baphetid stem tetrapods and its occurrence in stratigraphic proximity to
the land snail Dendropupa recall their association in the Hebert
sandstone of the Joggins Formation (Hebert and Calder 2004; Falcon-Lang
et al. 2004).
Flora
Plant compression assemblages
By far the most abundant macrofloral impressions are sphenopsid
stems (Calamites cistii and less commonly Calamites suckowii), which
occur throughout the section as prostrate axes in channel lag deposits,
and less commonly in growth position. Unfragmented Cordaites leaves, up
to 22 cm in length, are common locally in red mudrock beds and channel
sandstone bodies. Less commonly recorded are medullosan pteridosperm
axes, rare foliage (Alethopteris sp.) and seeds (Trigonocarpus cf.
parkinsonii). Lycopsid remains are very rare indeed, represented only by
leaf compressions (Cyperites sp.) at 220 m in the measured section, and
at 241 m, by trunk compressions (Lepidodendron sensu latu and Sigillaria
cf. rugosa). Stigmarian rootstocks are completely absent. An enigmatic
plant (Fig. 7) recovered from the measured section is similar to
Rhacopteris busseana (R.H. Wagner, personal communication, 2004), and
may represent a rarely encountered dryland or hinterland floral element.
Anatomically preserved woods
Multiple channel sandstone units, in particular those at 96 m and
240 m in the measured section, contin allochthonous charred blocks of
wood (up to 17 mm diameter), and more rarely calcite-permineralized
trunk fragments. These anatomically preserved woods are present both in
channel lags and in cross-bedded intervals higher in the channel bodies.
In addition, a single small mud-filled channel, hosted in a
mudrock-dominated interval at 352 in the measured section, contains a
further four calcite-permineralized trunks, 18-24 cm in diameter.
Scanning electron microscopy and thin section analysis shows all
specimens comprise pycnoxylic coniferopsid wood of Dadoxylon-type. The
best preserved examples are assigned to Dadoxylon recentium, a wood
characterized by biseriate, alternate, bordered tracheid pitting (Fig.
8A), cupressoid pits per cross-field (Fig. 8B, C), and low rays (Fig.
8D). In the Joggins Formation, Dadoxylon recentium wood has been
recorded in biological attachment to septate axes of Mesoxylon type
(Falcon-Lang 2003), indicating that at least some of the charred wood in
the Little River Formation is cordaitalean. However, some of the
calcite-permineralized woods in the Little River Formation are attached
to non-septate axes (up to 3-4 cm diameter, up to 45 cm long). At
present it is unclear whether the absence of pith septa is a biological
or taphonomic feature, but in either case, the most likely affinity of
these woods is cordaitalean (Falcon-Lang 2005).
DEPOSITIONAL ENVIRONMENT OF THE LITTLE RIVER FORMATION
Facies interpretation
Major channel sandstone bodies of the Little River Formation
represent the deposits of alluvial drainage channels. Channels are
characterized by moderate incision, subsequent infilling and, where the
rivers were shallow and broad, a final abandonment phase. These contrast
markedly with channel deposits of similar size associated with red
mudrock beds of the overlying Joggins Formation, which are incised and
confined within shallow valleys (Davies and Gibling 2003). The channel
forms of the Little River Formation facilitated aggradation, whereas
sediment bypass and cannibalization typified the Joggins paleochannels.
The flashy flow and rapid aggradation of the Little River Formation
drainage channels are indicated by a sigmoidal barform preserved at 95 m
(Fig. 5), which may represent a transitional antidune, and by sandy
wings, which record periods of maximum discharge when flow topped levees
(Friend et al. 1979). Sand-size clay grains, associated with this and
other channel complexes, may represent mud aggregates or finely ground
intraformational mud clasts indurated by drying and reworked from
floodplain deposits.
The presence of petrocalcic paleosol horizons indicates pronounced
rainfall seasonality and greater soil longevity than in the overlying
Joggins Formation, which is characterized by weakly developed, immature
paleosols (Smith 1991). Local gleyed horizons represent wetting or
ponding on the floodplain, which may have been facilitated by induration
of the dessicated mudrocks. Alternatively, rare Spirorbis-rich grey
mudstone beds may indicate cryptic transgressive events. Although the
ecological affinity of this fauna is poorly defined in the fossil record
with respect to marine or freshwater environments, it is locally
associated with brackish facies in the overlying Joggins Formation (Duff
and Walton 1973; Skilliter 2001; Falcon-Lang 2005). Although the red
beds generally reflect oxidizing, well drained conditions with
sufficient sediment input to prevent extensive pedogenesis, drab haloed
root compressions indicate that neither moisture deficit nor disturbance
prevented plant life.
The reproductive and growth strategies of the most common plant
groups within the Little River red beds show adaptation consistent with
the sedimentological record of periodic moisture deficit and aggrading
sediment. The persistence of calamiteans, perhaps the most ecologically
resilient of the Late Paleozoic plant groups (Calder et al. in press;
DiMichele et al. in press), was aided by their prolific vegetative
propagation by adventitious roots and underground rhizomes (Gastaldo
1992). Medullosan pteridosperms and cordaitaleans were assisted through
dry periods by a substantial root system, which allowed them to tap deep
groundwater sources (Falcon-Lang and Bashforth 2004). Although sparse,
the presence of lycopsid foliage and aerial stems in the upper
two-thirds of the section indicates that standing water was available
for their reproduction (Phillips and DiMichele 1992), at least
temporarily or in restricted areas of the landscape.
Stratigraphic relationships indicate that the red beds of the
Little River Formation were largely coeval with the conglomerates of the
Polly Brook Formation at the southern basin margin, which represent
extensive alluvial fan deposits derived from the Cobequid Highlands
massif to the south (Calder 1991, 1994). Paleoflow indicators within the
Little River Formation at Lower Cove, however, indicate a dominant
source to the northeast of the type section (potentially the Caledonia
Highlands), which argues against the Little River Formation as distal
deposits of the Polly Brook Formation alluvial fans. The immature,
feldspathic composition of certain horizons within the channel sandstone
bodies at 90 and 160 m suggests, however, that the Little River
Formation may include distal deposits derived from fans along the
Caledonia Highlands of southern New Brunswick. Equivocal support for
this hypothesis comes from the Grand Anse strata to the north and east
of the type section, which exhibit a coarser, more feldspathic
composition than at Lower Cove. As discussed earlier, however, the age
and fault boundaries of the Grande Anse cast uncertainty on correlation
of the two units.
Little River drylands as climate or topographic indicators
The clear evidence of prevailing dry conditions during deposition
of the Little River Formation speaks convincingly of climate as an
underlying control. However, the stratigraphic relationships within such
an active basinal setting also require consideration of topographic
factors that may have come into play in imparting the well-drained
character of these red beds. Evidence supporting a dry or dry seasonal
climate includes in situ pedogenic carbonate development, absence of
coal beds, flashy paleoflow recorded within channel bodies, and the
pervasive reddening of mudrocks and some sandstone bodies. The
possibility of topographically related drainage effects comes indirectly
from possible relationships with basin margin alluvial fan systems.
Although calcareous rhizoliths are present in the Joggins Formation
(Davies and Gibling 2003; Falcon-Lang et al. 2004), no in situ source
beds are present in that interval, nor within the Joggins Formation.
This raises the possibility of reworking from an upstream source, namely
the Little River Formation red beds. The absence of bivalve-bearing
beds, which record flooding events (Davies and Gibling 2003), suggests
that base level was not felt within the Little River environment, with
the possible exception of a single Spirorbis-rich interval. This further
suggests that gradient may have enhanced drainage and so have been a
factor in the development of the red beds. However, the general lack of
evidence of incision by channel bodies within the Little River
Formation, which would be expected if base level was lowered, does not
support the enhancement of drainage by topographic relief.
In summary, while there is cause for considering topographic
factors in draining the Little River drylands, the development of
calcareous soils, complete absence of coal beds and supporting
sedimentological evidence clearly required a climate regime with
pronounced dry intervals. Topographically enhanced drainage may have
played a contributing role.
CONCLUSIONS
The 635.8 m section of red beds at Lower Cove is sedimentologically
and stratigraphically distinct from adjacent units within the Cumberland
Basin, and so warrants designation as a separate formation, as first
recognized by Sir William Logan. Additionally, recognition of the Little
River Formation better circumscribes the definition of the overlying
Joggins Formation as coal-bearing and enhances its utility as a
regionally recognizable stratigraphic unit. These revisions (summarized
in Appendices B and C) confirm the pioneering work of Logan, and
formally elevate his Divisions 3 and 4 to formation status. The fluvial
style recorded in the Little River Formation records a dramatic change
from that of the underlying Boss Point Formation, although the onset of
reddening is presaged in the upper mudrocks of the Boss Point. This
dramatic cessation of the Boss Point fluvial systems and their
replacement by mudrich systems is also found in other depocentres of the
Maritimes Basin (Rehill et al. 1995). The landscape during deposition of
the Little River Formation was substantially better drained than that of
the succeeding Joggins Formation, including the seasonal dryland
environments (Falcon-Lang et al. 2004; Hebert and Calder 2004). The
absence of coal beds, pervasive reddening of mudrocks and sandstones and
development of pedogenic carbonate within the Little River Formation are
all consistent with xeric conditions and a pronounced dry season,
although topographic effects may have enhanced drainage. The Little
River red beds provide limiting constraints on the interpretations of
seasonal drylands in the succeeding Joggins Formation, which in contrast
records a gradual shift to wetter conditions with peat formation and
flooding events near base level.
ACKNOWLEDGEMENTS
The authors acknowledge the generous input received in the field
from their colleagues, in particular Susan Johnson of the New Brunswick
Department of Natural Resources. The financial support of the Cumberland
Regional Development Agency (CREDA) through its World Heritage
initiative made possible the digital transcription of the stratigraphic
logs (Appendix A), skillfully rendered by Andrew Henry. Howard
Falcon-Lang acknowledges receipt of a Killam Fellowship held at
Dalhousie University, and a NERC Fellowship (NCR/I/S/2001/00738) at the
University of Bristol. Doug MacDonald and Robert Naylor provided helpful
editorial and scientific comments on the initial draft of the
manuscript. The manuscript benefited greatly from the insightful reviews
and stratigraphic knowledge of Peter Giles and Susan Johnson, and
careful editing of Rob Fensome.
APPENDIX A
[ILLUSTRATION OMITTED]
APPENDIX B
Standard lexicon entry for the Little River Formation.
Author: Calder, Rygel, Ryan, Falcon-Lang and Hebert 2005
Type locality: Outcrop in the intertidal zone and low-relief
coastal bluffs on the eastern shore of Chignecto Bay, at Lower Cove,
near Joggins, Cumberland County, Nova Scotia. The type section begins at
the top (southern edge) of the South Reef of the Boss Point Formation
(UTM Coordinates 5066450N, 388000E; NAD 83 datum) and extends 1500 m
southwards to a point 500 m south of the mouth of Little River
(5063200N, 388400E). The top of the section coincides with the base of
the lowest coal bed (Coal 45 of Logan 1845) of the Joggins Formation,
near the start of the continuous cliff-section.
Lithology: A red bed succession dominated by mudrocks, which
exhibit pervasive mottling from root traces and local pedogenic
carbonate, with sandstone bodies typically 3-6 m thick. Coal beds and
bivalve-bearing limestones are absent.
Thickness and distribution: The type section at Lower Cove is 635.8
m in thickness. The formation can be traced 30 km to the east along the
north limb of the Athol Syncline to Styles Brook ("abundant red
beds" of Ryan et al. 1990a), where it eventually pinches out
between the underlying Polly Brook Formation and overlying Joggins and
Springhill Mines formations (Fig. 3). The Lower Cove beds exhibit many
similarities with fault-bound strata exposed to the west across
Chignecto Bay on Maringouin Peninsula, New Brunswick, assigned to the
informal Grande Anse formation (St. Peter and Johnson 1997) and strata
along strike at Minudie Point, Nova Scotia.
Relations to other units: The basal contact of the Little River
Formation is placed at the top of the highest multistorey sandstone bed
of the Boss Point Formation, which at the type section is the top of the
South Reef, coinciding with the base of Division 5 of Logan (1845).
Inland, to the east, the base of the formation progressively onlaps
against polymictic conglomerates of the Polly Brook Formation (Ryan et
al. 1990a). The upper contact of the formation is placed at the base of
the stratigraphically lowest coal bed, which at the type section is coal
45 of Logan (1845), 1.65m above the base of Logan Divison 4. This upper
contact defines the base of the revised Joggins Formation (Calder et al.
this paper, Davies et al. 2005). Although it is probable that the Grande
Anse formation in southeast New Brunswick may represent a facies of the
Little River Formation, the correlation of the two units is problematic
due to uncertainties in the stratigraphic relationship of the Grande
Anse formation with adjacent geologic units: the base of the Grand Anse
section is in faulted contact with the Boss Point Formation at the
coast, although the contact is reported to be conformable in the axis of
the Hardledges Syncline south of the Shepody-Beckwith Fault (Johnson
1996); the top of the Grand Anse section is in faulted contact with the
Mississippian Windsor Group. Johnson (1996) suggested correlation of the
Grande Anse with the Polly Brook Formation and lower Joggins (Little
River) Formation.
Age justification: Age determination of the Little River Formation
is problematic, due to its sparse paleontological record, and in
particular, the absence of key age-diagnostic marine index fossils
(Calder 1998). Palynostratigraphic studies of the type section place the
Little River Formation within the upper Namurian (Kinderscoutian) to
basal Westphalian (basal Langsettian) (Dolby 1991, 2003; Utting and
Wagner 2005).
History: First mapped by Logan (1845), the Little River Formation
coincides almost precisely with his Division 5. Dawson (1855) originally
included these strata in his "Lower or Older Coal Formation",
but later (Dawson 1868) referred them to his "Millstone-grit
Series". Bell (1912, 1914) included the Lower Cove red beds in his
Joggins Formation, but later abandoned the term (Bell 1938, 1944). Ryan
et al. (1991) reconstituted the Joggins Formation to be inclusive of the
Lower Cove red beds but Ryan et al. (1990a) mapped their boundary with
the Joggins Formation inland.
References: Bell 1912, 1914, 1938, 1944; Calder et al. this paper;
Davies et al. 2005; Dawson 1855, 1868; Dolby 1991, 2003; Johnson 1996;
Logan 1845; Ryan et al. 1990a; Ryan et al. 1991, Utting and Wagner 2005.
APPENDIX C
Standard lexicon entry for the Joggins Formation.
Author: Calder, Rygel, Ryan, Falcon-Lang and Hebert 2005; Davies,
Gibling, Rygel and Calder 2005.
Type locality: Outcrop in the coastal cliffs and wave-cut platform
on the eastern shore of Chignecto Bay, near the village of Joggins,
Cumberland County, Nova Scotia. The base of the type section coincides
with the base of the lowest coal bed (Coal 45 of Logan 1845) near the
start of the continuous cliff-section south of Little River (UTM
Coordinates 5063200N, 388400E, NAD 83 datum) and extends 2800m
southwards to a point south of Bell Brook and north of Dennis Point
(5060700N, 386950E) that coincides with the top of the uppermost
limestone unit.
Lithology: A coal-bearing succession comprising grey,
siderite-bearing and reddish mudrocks, grey sandstones ranging from 3-30
m thick (Rygel 2005), bituminous coal beds typically less than one metre
in thickness and associated black bivalve-bearing limestones and shales;
all occurring in cycles from 16-212 m thick (Davies and Gibling 2003).
Thickness and distribution: The type section at Joggins is 915.5 m
thick (Davies et al. 2005). Within the Cumberland Basin, the formation
can be traced inland continuously for 40 km to the east along the north
limb of the Athol Syncline, where it thins dramatically (Copeland 1959;
Waldron and Rygel 2005). The formation persists as far south as
Springhill, where it pinches out against, and apparently onlaps, the
Polly Brook Formation (Ryan et al. 1990a; Calder 1991, 1994). To the
east, in the Wallace Syncline, it has been mapped through drilling in
the Roslin area (Calder and Naylor 1985; Ryan et al. 1990c). The Joggins
Formation is lithologically similar to the bivalve-bearing coal measures
assigned to the Port Hood Formation of western Cape Breton Island, and
bears lithologic similarities to the Parrsboro Formation in the Minas
Basin south of the Cobequid Highlands, although bivalve-bearing shale
sequences there attain greater thickness.
Relations to other units: The basal contact of the Joggins
Formation is placed at the base of the lowermost coal bed, which at the
type coastal section is coal 45 of Logan (1845). This contact is shared
conformably with the older Little River Formation, a lithologically
distinct non-coal-bearing, red bed unit (Calder et al. this paper). The
formation thins to the east and south, where it overlaps the Little
River red beds and progressively onlaps coarse basin margin
conglomerates of the Polly Brook Formation (Ryan et al. 1991). The upper
contact of the formation is given as the top of the uppermost limestone
(Davies et al. 2005), which at the type section occurs in coal group 1
of Logan (1845). The upper boundary is conformable with the basal
boundary of the Springhill Mines Formation which also is coal-bearing
but devoid of continuous fossiliferous limestone beds.
Age justification: The age of the Joggins Formation has long been
held to be early Westphalian, although precise correlation with European
stages has been hindered by lack of open marine index fossils. Bell
(1944) gave the age range as late Westphalian A-early B on the basis of
macroflora but favoured an early Westphalian B (Duckmantian) assignment,
later supported by Hacquebard and Donaldson (1964). Extensive
palynostratigraphic analysis of the Joggins and inland sections by Dolby
(1991) led him to revise the age downward to Westphalian A
(Langsettian). Subsequent palynostratigraphic and macrofloral analysis
have recognized Namurian elements within the paleobotanical record but
place the Joggins Formation most parsimoniously within the basal
Westphalian (early Langsettian). (Calder et al., in press; Utting and
Wagner 2005)
History: First mapped by Logan (1845), the Joggins Formation
coincides almost precisely with his Division 4. Dawson (1868) originally
included these strata in his "Middle Coal Formation". Bell
(1912, 1914) introduced the name Joggins Formation but later abandoned
the term (Bell 1938, 1944) due to difficulties in mapping the unit
inland, a problem that arose in part due to inclusion of the Lower Cove
red beds of Logan's Division 5 (Little River Formation of Calder et
al. this paper) and in part due to his correlation of the Joggins
Formation with younger coal-bearing strata at Spicer Cove. Subsequently,
Shaw (1951) referred these same strata to his informal
"coal-bearing facies". Copeland (1959) designated the Joggins
coal-bearing strata, exclusive of the Little River red beds, as his
informal "Facies B". Ryan et al. (1991) reconstituted the
Joggins Formation to be inclusive of the Little River Formation red
beds, although the lithological distinctiveness of the two units was
recognized as a mappable boundary by Ryan et al. (1990a). Calder et al.
(this paper) formally recognized the lower 635.8m red bed succession as
the Little River Formation, and re-established the Joggins Formation as
a coal- and bivalve limestone-bearing unit. Davies et al. (2005) suggest
that the upper boundary of the Joggins Formation be modified to coincide
with the top of the uppermost limestone unit as originally proposed by
Logan in his Division 4. This suggestion is formalized in the present
paper.
References: Bell 1912, 1914, 1938, 1944; Calder 1991, 1994; Calder
and Naylor 1985; Calder et al. this paper; Calder et al., in press;
Davies and Gibling 2003; Davies et al. 2005; Dawson 1868; Dolby 1991;
Hacquebard and Donaldson 1964; Logan 1845; Ryan et al. 1990a; Ryan et
al. 1991, Rygel 2005; Utting and Wagner 2005; Waldron and Rygel 2005.
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Editorial responsibility: Robert A. Fensome
JOHN H. CALDER (1) *, MICHAEL C. RYGEL (2), R.J. RYAN (1), HOWARD
J. FALCON-LANG (3) AND BRIAN L. HEBERT (4)
* corresponding author
(1.) Nova Scotia Department of Natural Resources, P.O. Box 698,
Halifax, Nova Scotia, B3J 2T9, Canada
(2.) Department of Earth Sciences, Dalhousie University, Halifax,
Nova Scotia, B3H 3J5, Canada
(3.) Department of Earth Sciences, University of Bristol, Bristol
BS8 1RJ, U.K.
(4.) RR 1, Joggins, Nova Scotia, BOL 1A0, Canada
Date received: 14 January 2005 [paragraph] Date accepted: 9 August
2005