NORWEGIAN JOURNAL OF GEOLOGY
Paralic sedimentation on an epicontinental ramp shelf 343
Paralic sedimentation on an epicontinental ramp shelf
during a full cycle of relative sea-level fluctuation; the
Helvetiafjellet Formation in Nordenskiöld land, Spitsbergen
Ivar Midtkandal, Johan Petter Nystuen and Jenö Nagy
Ivar Midtkandal, Johan Petter Nystuen & Jenö Nagy. Norwegian Journal of Geology, vol. 87, pp. 343-359.Trondheim 2007. ISSN 029-196X.
A depositional model for the development of the Helvetiafjellet Formation in Nordenskiöld Land, Spitsbergen is presented. The formation was
deposited into a segment of the large epicontinental Boreal basin that rimmed northern Pangaea during the Early Cretaceous. A wide range of
depositional subenvironments are recorded within the succession; including fluvial braidplain, shallow marine bay, delta, coastal plain and fluvial
channel. The depositional model approaches a layer-cake style for this part of the basin, caused by the rapid rates of progradation and retrogradation made possible by the gentle depositional gradient. An initial period of fluvial deposition arose in response to an early rise in relative sea-level.
Following a regional flooding, the progradational to aggradational architecture in the area reflects a balanced rate of increase in accommodation vs.
rate of sedimentation (A/S) ratio. This resulted in a heterolithic stacking of sandstone and mudstone. Autogenic variables are thought to have dominated the lateral facies variations recorded in the upper and middle parts of the succession.
Ivar Midtkandal (ivar@midtkandal.no), Johan Petter Nystuen (j.p.nystuen@geo.uio.no,) Jenö Nagy (jeno.nagy@geo.uio.no). Department of Geosciences, University of Oslo, P.O Box 1047 Blindern, NO-0316 Oslo Norway
Introduction
Basin physiography is a major factor controlling sedimentary infill patterns. The relative influence of basin
physiography varies between different basin types; tectonically active or passive, deep or shallow, large or small
(Allen & Allen 2005). The present study deals with sediment infill and variation in facies and sedimentary architecture in an epicontinental basin with a low-sloping,
wide ramp shelf setting dominated by paralic depositional environments.
The bathymetric profile of an epicontinental basin generally shows a gradual deepening towards the basin centre. Shelf breaks may be absent or only weakly developed.
However, any topography inherited from the submerged
continental plate of such a basin can potentially affect
drainage and depositional architecture (Fagherazzi et al.
2004). Slope gradients may be an inherited property, or
may be caused by tectonic activity during basin development. Variations in relative sea-level on low-gradient shelves may give rise to long-distance basinward or
landward shifts in facies, coupled with total emergence
or complete submergence of the shelf. Moderate, highfrequent sea-level variations do not necessarily cause significant changes in overall facies stacking patterns, due to
the relatively constant basin floor gradient and tectonic
stability of the shelf area. Minor fluctuations in sea-level
may trigger changes in coastal morphology, and variations in relative impact on sediment partitioning by flu-
vial, tidal and wave-induced currents. Autogenic variables
such as river avulsions and delta lobe shifts, together with
variation in sedimentary regime parameters may contribute to lateral, as well as vertical variation in depositional environment and facies (Swift & Thorne 1991).
The relative influence of allogenic and autogenic factors on the depositional architectural style is considered
important in very low-sloping ramp shelf basins, as it
influences modelling procedures significantly for this
type of sedimentary succession. The horizontal scale of
variation in depositional architectural elements is furthermore considered particularly crucial for modelling
epicontinental basin successions, as emphasised for other
types of depositional environments (Miall 1988; Walker
1992). Modelling studies have also shown that a wide
variety of depositional styles may develop with identical
sea-level, tectonic and sediment supply histories (Carey
et al. 1999). This complicates any attempt to reconstruct
sedimentary relationships in basin settings with very low
resolution of the depositional relief. Several large epicontinental basins developed as a result
of a global sea-level rise during the Cretaceous (Grocke
et al. 2003). One of these was the Boreal basin at the
northern margin of Pangaea, predating the opening of
the Polar basin and the northeasternmost Atlantic in the
Late Cretaceous to Early Cenozoic (Torsvik et al. 2002).
The object of the present study is to describe depositional patterns and facies variation within the Barremian
344 I. Midtkandal et al.
NORWEGIAN JOURNAL OF GEOLOGY
N
n=124
W
E
Kong Karls Land
S
SPITSBERGEN
mean=138˚
78 22’ 08’’
Sassenfjorden
Forkastningsfjellet
Wimanfjellet
Criocerasaksla
Konusen
Log trace
positions
2
15 40’
138˚
15 20’
1
Janusfjellet
Hanaskogdalen
Nordenskiold
Land
500 m
250 m
1000 m
Longyearbyen
Helvetiafjellet
3 km
N
78 10’ 15’’
Section 1, Fig. 5
Section 2, Fig. 6
Sassenfjorden
log traces
100 m
1 Km
Hanaskogdalen
Fig. 1. Map of Svalbard with the studied field area in central Spitsbergen enlarged. The profiles marked by 1 and 2 correspond to Figs. 5 and 6,
respectively and illustrate the difference in scales between the two correlation panels. The rose diagram shows the palaeocurrent directions for
the area, with a mean direction of 138˚.
Helvetiafjellet Formation of Spitsbergen. This formation
developed in a fluvial to paralic setting during a period
of fall and rise in relative sea-level at the ramp margin of
the Boreal epicontinental basin in the Svalbard domain.
Vertical stacking patterns and lateral variations in facies
associations, as controlled by processes and factors mentioned above, form the central theme of this paper.
Geologic framework and depositional
models of the Helvetiafjellet Formation
The study area lies in Nordenskiöld Land on Spitsbergen, the largest island in the Svalbard archipelago, Norway. Here, several hundred meters of Mesozoic strata are
intermittently exposed. Svalbard was located at roughly
60˚N in the Late Jurassic to Early Cretaceous (Steel &
Worsley 1984; Torsvik et al. 2002), and formed part of
Paralic sedimentation on an epicontinental ramp shelf 345
NORWEGIAN JOURNAL OF GEOLOGY
the Boreal basin, which also included the Sverdrup Basin,
the Alaskan Basin and basins at northern Greenland.
The area was a shallow epicontinental sea (Harland et al.
1984; Torsvik et al. 2002; Nagy 1970), with a low-angle,
gradually deepening shelf from shoreline to basin centre.
The Boreal basin was, during the Early Cretaceous,
affected by tectonic and magmatic processes associated with the development of a Large Igneous Province
(LIP) to the north and east, with subaerial lava flows
interfingering with Helvetiafjellet Formation sands on
Kong Karls Land (Mørk et al. 1999; Maher 1999). This
is a small group of islands about 100 km offshore eastern
Spitsbergen, exposing the easternmost exposures of the
formation (Fig. 1). Volcanic ashes (bentonites) have been
recorded in the upper part of the Helvetiafjellet Formation at Festningen, western Spitsbergen (Pers. comm.
Hans Amundsen, Physics of Geological Processes, University of Oslo) and elsewhere in Spitsbergen (Mørk et
al. 1999). Dolerite sills intruded the underlying shale succession (the Janusfjellet Subgroup) in eastern Spitsbergen in the Barremian, possibly during the development
of the Helvetiafjellet Formation (Miloslavskij et al. 1992).
During the Barremian, the climate was humid, supporting peat (coal) accumulation and a dinosaur population
(Nøttvedt et al. 1992; Hurum et al. 2006). Temperature
gradients were low, and did not change much during
the Barremian stages (Fischer 1981; Ziegler et al. 1987;
Nemec 1992).
The Helvetiafjellet Formation is a 12-155 m thick shallowmarine to fluvial sandstone-dominated succession which
Age
Lithology Thickness Lithostratigraphic
(shale/sst)
(m)
subdivision
Depositional
environment
Albian
Shallow to distal
marine shelf
Barremian
12
155
Helvetiafjellet
Fm
110
400
Rurikfjellet
Fm
90
350
Agardhfjellet
Fm
Hauterivian
Valanginian
Adventdalen Group
Aptian
Early
Cretaceous
190 Carolinefjellet
Fm
?1200
Fluvial and paralic
Regressive open
marine shelf
Berriasian
Late
Jurassic
Volgian
Kimmeridgian
Oxfordian
Open marine shelf
Callovian
Fig. 2. Svalbard’s Mesozoic succession, compiled from Mørk et al.
(1999).
overlies an up to 800 m thick mudstone-rich interval,
the Janusfjellet Subgroup (Fig. 2). The Rurikfjellet Formation (Parker 1967), being the upper mudstone unit
in this subgroup, was deposited under open marine oxic
shelf conditions. In its upper part, the Rurikfjellet Formation generally shallows upwards through repeated sets
of upward-coarsening parasequences of shore-face and
delta lobe deposits (Dypvik 1980; Dypvik 1985; Dypvik
et al. 1991; Mørk et al. 1999). The boundary towards
the overlying Helvetiafjellet Formation has been a matter of discussion and is of critical importance for the
depositional system of the Helvetiafjellet Formation (see
below). Stratigraphically above the Helvetiafjellet Formation, the Carolinefjellet Formation (Parker 1967; Nagy
1970; Mørk et al. 1999) was deposited after a regional
transgression that brought about a return to the conditions of an open marine shelf environment.
Several studies discuss the Helvetiafjellet Formation, its
stratigraphy, facies and depositional conditions (Róžycki
1959; Parker 1967; Birkenmajer 1975; Edwards 1976;
Steel 1977; Edwards 1978; Steel et al. 1978; Edwards 1979;
Edwards et al. 1979; Nemec et al. 1988a, b; Grosfjeld 1992;
Nemec 1992; Nøttvedt et al. 1992; Gjelberg & Steel 1995;
Prestholm & Walderhaug 2000; Steel et al. 2001; Maher et
al. 2002; Midtkandal 2002; Maher et al. 2004; Ahokas et
al. 2005; Midtkandal et al. 2005).
The Helvetiafjellet Formation was named in a description
of the Jurassic and Cretaceous stratigraphy of Spitsbergen
by Parker (1967); it is this description that is currently
in use (Mørk et al. 1999). Dealing with the formation in
Nordenskiöld Land, Steel (1977) described and discussed
the variability of sandstone deposits in deltaic settings,
including a wide range of subenvironments. The local
variability of sandstone bodies, and how depositional
subenvironments interfinger laterally in a deltaic coast
setting, was demonstrated. Steel and Worsley (1984) and
Nemec (1992) presented general depositional models for
the Helvetiafjellet Formation, with emphasis on the fluvial character of the Festningen sandstone member and
the variability of depositional environments that form
the middle to upper parts of the formation.
The original model for the internal stratigraphy of the
Helvetiafjellet Formation (Parker 1967; Nagy 1970) was
of layer-cake type, whereas models advocated by Steel
and Worsley (1984) and Nemec at al. (1988a, b) outlined
the development of a retrogradational delta complex.
Gjelberg and Steel (1995), reviewing these models, suggested a third depositional model for the sequence stratigraphic development of the Helvetiafjellet Formation.
Their model comprises a backstepping palaeo-shoreline
and an overall regressive development linked to a rise
in relative sea-level throughout the temporal and spatial extent of the Helvetiafjellet Formation. An important feature in the model of Gjelberg and Steel (1995) is
that all fluvial sandstone bodies are clastic wedges that
lithostratigraphically can be linked upstream to the Fest-
346 I. Midtkandal et al.
NORWEGIAN JOURNAL OF GEOLOGY
log trace, Konusen E
FA7
log trace, Konusen W
FS2
FA5
FA6
FA4
E
FA2
FS1
FA3
W
FA1
SB
FA7
20 m
Fig. 3. Northern slope of Konusen, showing a typical Helvetiafjellet Formation outcrop on the southern shore of Sassenfjorden, Nordenskiöld
Land. The log traces marked on either side of the cliff section correspond to the logs with the same name in Fig. 5. The lowest sandstone body is
the Festningen sandstone (FA1), a fluvial braidplain deposit that rests unconformably on the regional sequence boundary.
a
b
FA2
FA4
FS1
15 m
FA3
15 m
FA2
FA1
FA7
E
SB
FS1
FA1
W
E
d
FA4
FA4
5m
c
W
8m
FA3
FA4
FS1
FA3
FA1
E
W
W
f
20 cm
e
FA5
E
FA2
FA5
FA6
15 m
FA5
FA5
E
FA4
W
h
g
FA1
Carolinefjellet
Formation
SB
W
2m
FA7
E
Helvetiafjellet
Formation
Rurikfjellet
Formation
E
W
Fig. 4. Facies associations recorded in the
Helvetiafjellet Formation (and Rurikfjellet Formation). a) FA1; braided fluvial
channel belt overlying the regional sequence boundary (SB) at Konusen. Notice
the sandstone bar forms that prograde
towards the left (east), and the progressive thinning of sandstone beds towards
the upper boundary of FA1. b) FA2;
Interdistributary bay or lagoon with thin
interbeds of FA3 (delta lobe toeset) in the
upper part (at Konusen). The FA3 beds
thin and pinch out towards the left (east).
c) FA3; delta lobe toesets at Hanaskogdalen west. The FA3 deposits are stacked to
form a 6-7 m thick sandstone-rich unit
at this locality (Hanaskog 1 west). Notice
the sandstone-sandstone contact to the
underlying FA1 deposit. d) FA4; delta
lobe front and top at Hanaskogdalen.
The locality displays the conformable
transition from lagoon/interdistributary
bay, into delta lobe toeset and further on
to delta front deposits. Notice the mudstone wedges that separate the lower toeset beds. e) Coastal floodplain deposits at
Janusfjellet. The image shows thin-bedded sandstone with mud- and coal drapes. Photo by Kjell Ove Storvik. f) FA6;
fluvial channel deposits dissecting coastal
floodplain sediments at Konusen. The
fluvial channels are laterally discontinuous and show significant thickness variations. g) FA7; open marine deposits at
Hanaskogdalen. The layered sandstone
beds behind the person are Facies F, hummocky cross stratified sandstone beds at
the top of the Rurikfjellet Formation. The
regional sequence boundary (SB) marks
the upper contact of FA7. Notice the bar
forms that downlap onto the SB in FA1.
h) The Wimanfjellet locality, Sassenfjorden. The Festningen sandstone forms an
easily recognizable cliff, but makes accessibility problematic.
Paralic sedimentation on an epicontinental ramp shelf 347
NORWEGIAN JOURNAL OF GEOLOGY
ningen sandstone member, within the Spitsbergen domain.
This was due either to a fall in relative sea-level or by
coastal plain progradation within an overall backstepping transgressive systems tract. The model also assumed
a conformable contact existed between the Helvetiafjellet
Formation and the underlying Rurikfjellet Formation in
the south-eastern part of Spitsbergen. Parker (1967) and
later studies (Edwards 1976; Nøttvedt et al. 1992; Mørk
et al. 1999; Midtkandal et al. in review) have described
the lower boundary of the Helvetiafjellet Formation generally as an erosional unconformity.
The Nordenskiöld Land study area
The Nordenskiöld Land study area lies to the NE of
Longyearbyen, Svalbard (Fig. 1). The outcrops included
in this study are grouped into two cliff sections oriented
roughly ENE along the northern side of Hanaskogdalen
and along the southern shore of Sassenfjorden (Fig. 1).
A moderately well exposed 1000 m long cliff section is
exposed in Hanaskogdalen, distributed over 3 locali-
ties, whereas the Sassenfjorden area provides excellent
exposures over a distance of 7 km, here represented by 6
localities. Accessibility is hazardous; especially in the Sassenfjorden localities, where the majority of the cliff sections cannot be visited due to the steepness of the slopes
(Fig. 3). Palaeocurrent measurements of beds in the Helvetiafjellet Formation in this area indicate a mean flow
direction of 324˚, roughly SSE. Thus, the field data allow
for the construction of two sub-parallel oblique-dip sections based on semi-continuous cliff exposures, and a 3D
reconstruction of the depositional development in the
area can be inferred from a correlation between the Sassenfjorden and Hanaskogdalen outcrops.
Facies and facies associations
In Nordenskiöld Land, thirteen sedimentary facies, designated A to M, have been defined in the Helvetiafjellet
Formation and in the adjacent parts of the under- and
overlying formations, the Rurikfjellet and Carolinefjellet formations, respectively (Table 1). These facies occur
Table 1. Facies recorded in the Helvetiafjellet Formation in Nordenskiold Land
Facies
Description
Grain size
Interpretation
A
Extrabasinal clasts (chert, quartzite, crystal- Medium to very coarse sand
line quartz) in sandstone matrix. Matrix
matrix, max. clast size 12 cm.
supported. Lower boundary erosive, gradational upper boundary into Facies B.
High energy fluvial channel base conglomerate.
B
Trough cross-stratified sandstone with
extrabasinal clasts at foreset basal boundaries and upward fining foresets. Tangential
bottomset terminations. Scattered mudstone clasts.
Medium to very coarse sand.
Extrabasinal clasts up to 1.5 cm
in diameter.
Fluvial channel deposition as 3D dunes with
sufficient energy to cause flow separation over
dune crests.
C
Tabular cross-stratified sandstone with
extrabasinal clasts at some foreset basal
boundaries. Angular foreset terminations.
Medium to coarse sand. Extrabasinal clasts up to 1 cm in
diameter.
Fluvial channel deposit formed as 2D dunes.
No flow separation at dune crests.
D
Plane-parallel stratified sandstone
Medium to coarse sand
Upper flow regime fluvial channel deposition
E
Massive structureless sandstone
Fine and medium sand
Rapid deposition from suspension in a fluvial
system
F
Hummocky cross- stratified sandstone
Very fine to fine sand
Offshore transition to open shelf sedimentation.
Deposition below normal wave base.
G
Asymmetrical ripple laminated sandstone
Very fine to fine sand
Lower flow regime deposition in unidirectionally
flowing water
H
Symmetrical ripple laminated sandstone,
chevron type
Very fine to fine sand
Deposition in shallow, standing body of water
during horizontal oscillation
I
Plane parallel laminated siltstone and
sandstone
Silt and very fine sand
Deposition from suspension in very low energy
conditions
J
Interbedded sandstone and mudstone
Mud and very fine to fine sand
Deposition in alternating low and zero energy at
any water depth. Can be marine or lacustrine in
origin
K
Mudstone, black and grey with planeparallel lamination
Mud
Deposition from suspension in standing water
L
Coal
Mud
Formed in areas with low sediment influx and
high organic production, such as marshes or
swamps
M
Cross-stratified sandstone with double
mud drapes
Very fine to fine sand
Fluvially deposited bedforms modified by tidal
currents.
348 I. Midtkandal et al.
within seven facies associations (Table 2). The facies associations FA1 to FA7, here listed according to their order
of stratigraphic appearance, thus reflect roughly how the
sedimentary environment changed over time (Table 2).
FA1 Braided fluvial channel belt
Description
A sandstone body, ranging from 15-25 m in thickness,
forms the lowermost lithostratigraphic unit of the Helvetiafjellet Formation in Nordenskiöld Land. The sandstone has traditionally been referred to the Festningen sandstone member (Mørk et al. 1999). The lower
boundary is clearly erosive, marking an abrupt change
in lithology from mudstone (Facies K) to conglomerate
(Facies A), the latter dominating the lower 1-3 m of this
stratigraphic unit. The unit furthermore includes beds
of facies B (trough cross-stratified sandstone), C (tabular cross-stratified sandstone), D (plane-parallel stratified sandstone) and E (massive structureless sandstone)
(Tables 1 and 2). FA1 is a complex of numerous interfingering multi-storey, multi-lateral lens-shaped bodies of
sandstone, 2-5 m thick and several tens of meters long.
Lens thicknesses vary as both upper and lower boundaries undulate and pinch out in all directions (Fig. 4 a).
Two orders of surfaces are observed within the FA1 sandstone unit at the Konusen locality (Fig. 3); the highest
order surface dips gently with a component in the downstream direction, and forms low-angle, large scale clinothemes that span the length of the outcrop (~1 km). The
lower order surface marks boundaries between discrete
bars that comprise most of the lower half of this unit.
Both boundaries are sandstone-sandstone contacts, and
can be identified at a distance from the outcrops. Palaeocurrent directions generally deviate less than ±45˚ from
a mean direction of 138˚ (Fig. 1). Vertical trends in the
sandstone succession are upward fining in the lower third
of the unit, and upward thinning of beds in the upper
third. The uppermost beds of FA1 are generally 40-60%
thinner than those in the lower half of the unit, with correspondingly reduced bar form sizes, both in the vertical
and lateral directions. The lateral extent of FA1 is far beyond the outcrop area
of Nordenskiöld Land and has been recorded in several
outcrop areas across Spitsbergen (Birkenmajer 1975;
Edwards 1976; Steel et al. 1978; Edwards 1979; Nemec
1992; Maher et al. 2004; Midtkandal et al. in review).
Interpretation
Based on lithology, sedimentary structures, low palaeocurrent direction divergence and absence of fine grained
beds, the FA1 sandstone succession is interpreted to represent a braided fluvial channel belt, as has been previously documented by Nemec (1992). The lens-shaped
sandstone bodies represent mid- and lateral channel bars,
mainly accreting in the downstream direction, second-
NORWEGIAN JOURNAL OF GEOLOGY
arily in lateral directions (Figs. 4, 5 and 6). The undulating upper and lower bar boundaries reflect how the braid
bars merge into each other and coalesce in all directions
due to the presence of sand everywhere on the channel
floor. The highest order of surfaces that cut through the
unit at a low angle probably represents bypass surfaces
that developed while the unit was being formed. High
influx rates of sediment coupled with limited vertical
accommodation space is thought to have caused intermittent bypass and erosion as sediments were being
transported into the lowest topographic areas available at
any given time. The second order of intra-sandstone surfaces represent braid bar boundaries, formed in episodes
of active downstream and/or lateral accretion followed
by scouring, when the local channel thalweg shifted,
thus changing the main direction of sediment transport.
The complete absence of mudstone beds suggests high
channel mobility, making peat accumulation impossible
(Nemec 1992). Upward thinning of beds and bedforms
in the upper third of FA1 is here ascribed to an overall
waning of current energy. Channel abandonment due to
lateral migration, reduction of runoff rates, or increased
rate of rise in base level during deposition are possible
explanations for the upward thinning of beds.
The lower boundary of FA1 represents a significant
regional basinward shift in facies, from open marine
mud accumulation in the underlying Rurikfjellet Formation, to subaerial erosion, followed by fluvial deposition.
This boundary surface is suggested to represent a type 1
sequence boundary in the sense of Posamentier & Vail
(1988), Van Wagoner et al. (1988) and Van Wagoner et
al. 1990).
FA2 Interdistributary bay or lagoon
Description
FA2 overlies FA1, with an abrupt lithological change from
Facies C (tabular cross stratified sandstone) to Facies K
(mudstone) (Table 1). The boundary appears to be horizontal with no visible signs of erosion. FA2 is dominated
by Facies K (Fig. 4 b), and forms a 5-15 m thick, darkcoloured stratigraphic unit that extends laterally beyond
the outcrop area of Nordenskiöld Land. Accurate thickness measurements of this unit are difficult to obtain due
the unconsolidated nature of the mudstone beds, and
scree-covered nature of the outcrops (Fig. 3).
At various stratigraphic levels within this mudstone succession, sandstone intercalations up to 1.5 m thick occur,
representing four facies: G (asymmetrical ripple laminated sandstone), H (symmetrical ripple laminated sandstone), I (plane-parallel laminated silt- and sandstone)
and J (interbedded sandstone and mudstone) (Tables 1
and 2). Individual beds are 10-50 cm thick and appear
vertically stacked. The beds can commonly be traced
along cliff sections for hundreds of meters, but correlation between log traces is difficult due to poor exposures
between localities. At Konusen, (Fig. 3) the beds decrease
NORWEGIAN JOURNAL OF GEOLOGY
in thickness eastwards.
FA2 varies internally and contains both very finely laminated, pure mudstone and intervals with a coarser clastic component. In a sample taken from finely laminated
dark mudstone at the Konusen site, the following three
foraminiferal taxa have been documented: Trochammina
sp., Ammobaculites sp. and Verneuilinoides sp.
Interpretation
The low diversity, agglutinated nature of the foraminiferal assemblage occurring in the FA2 mudstone indicates
a restricted marine environment. This means that conditions diverged from those of a normal marine shelf. The
small size of the observed specimens supports this interpretation. The main restricting factor was apparently
reduced salinity in an interdistributary bay or lagoon.
In addition, moderately hypoxic conditions might have
occurred in the lower part of the water column owing to
salinity-induced stratification in a shallow depositional
area with high organic supply. The finely laminated dark
mudstone lithology of the FA2 beds is in accordance with
such stagnant bottom conditions
Further support for this interpretation is provided
by comparisons with modern and ancient analogues,
although comparisons with modern faunas are complicated owing to major evolutionary changes in foraminiferal assemblages during the Late Cretaceous and Tertiary.
The dominant species in the FA2 sample is Trochammina
sp., which is similar to small-sized representatives of Trochammina previously reported as dominant in Jurassic
and Paleogene mudstones and indicative of a hyposaline, delta-influenced environments (Nagy et al. 1990;
Nagy 2005). The same genus is also dominant in several
modern brackish lagoons, with a salinity-stratified water
column where hypoxic bottom conditions develop seasonally (Takata et al. 2005; Takata et al. 2006). Ammobaculites is reported as common to dominant in Jurassic
brackish prodelta deposits (Nagy & Seidenkrantz 2003).
In modern faunas this genus is often associated with low
salinity estuarine conditions (Busas 1974; Murray 1991).
Verneuilinoides and related serial forms are reported to be
as common in Paleogene lagoonal sections (Nagy 2005),
and in modern hyposaline waters (Alve 1990).
From these micropaleontological data it is apparent
that FA2 was deposited in a restricted, shallow, marginal
marine environment such as an interdistributary bay or
lagoon. Palaeo water depths were shallow, as in modern
lagoons or interdistributary bays, allowing variations
in clastic detritus to mix with the mud. The sandstone
beds within FA2 may represent a range of coastal shallow
marine deposits. Some or all of these beds probably form
distal parts of the succeeding facies association, FA3, delta
lobe toe set (see below). During periods of increased sedimentation rates, deltaic sands may have been deposited
further out beyond the shoreline than is the case under
Paralic sedimentation on an epicontinental ramp shelf 349
average conditions. Alternatively, a portion of the sandstones may have formed as sand spits or as a result of
any combination of processes that form sand drapes in
shallow marine environments, such as storm surges and
neap/spring tides.
An abrupt shift from a coarse grained fluvial (FA1) to a
marginal marine environment indicates flooding of the
area. The lower boundary of this facies association is
henceforth termed FS1 (Figs. 3, 4, 5, and 6), and represents a potentially regional significant flooding surface.
In this low-gradient setting, this flooding is inferred to
have been rapid and widespread, thus making this surface applicable as a datum plane for correlation, as is discussed below.
FA3 Delta lobe toe set
Description
In the western, proximal, Hanaskogdalen localities (Fig.
6), a 6-7 m thick interval of thin-bedded (5-15 cm)
sandstone directly overlies the lowest fluvial unit in the
Helvetiafjellet Formation (FA1). The entire interval consists of Facies D (plane parallel stratified sandstone) and
J (interbedded sandstone and mudstone) (Tables 1 and
2). The lower boundary is lithologically sharp, but without any observed erosional features. The sandstone beds
are stacked conformably with a thin (mm) mudstone
drape marking bed boundaries (Fig. 4 c). Bed thickness
decreases slightly from 10-15 cm upwards to about 5-10
cm, and grain size is reduced from fine to very fine sandstone in the upper 2 m of the unit. The western, proximal, continuation of FA3 is located beyond the outcrop
area in Hanaskogdalen, and is thus not exposed here for
observation. The eastern, distal extension of FA3 is also
covered but at the next log trace downstream from the
western Hanaskogdalen localities (Hanaskogdalen 1
West), this interval is replaced by a mudstone dominated
succession (FA2, interdistributary bay or lagoon) of corresponding thickness. The boundary to the succeeding
stratigraphic unit, FA4 (described below), is an abrupt
shift into Facies C (tabular cross stratified sandstone),
with no visible sign of erosion.
Similar sandstone successions are recorded within the
stratigraphic interval marked by FA2 in the Sassenfjorden area, and may correlate with this unit (see discussion
under FA2, above).
Interpretation
FA3 is interpreted to represent delta toe set deposits. The
distal facies transition into FA2 mudstone facies suggests a shallow water hyposaline environment where thin
sheets of sand at the front of a delta lobe pinch out basinwards (east). The lower boundary of FA3 is identified as
the same flooding surface, FS1, as previously mentioned
(Figs. 3, 4, 5 and 6).
350 I. Midtkandal et al.
FA4 Delta lobe front and top
Description
FA4 is a succession of variable thickness (2-9 m) and is
composed of Facies C (tabular cross-stratified sandstone), D (plane-parallel stratified sandstone), E (massive structureless sandstone), G (asymmetrical ripplelaminated sandstone), H (symmetrical ripple-laminated
sandstone), I (plane-parallel laminated silt- and sandstone), and J (interbedded sandstone and mudstone),
K (mudstone), and L coal (Tables 1 and 2). The lower
boundary of FA2 is conformable, recorded as an upward
coarsening from FA4 mudstone into fine sand (facies D
and E) over an interval of less than 1 m. In the entire outcrop area, the unit forms a sandstone body of relatively
constant thickness that exceeds the aerial limits of outcrop included in this study.
A series of eastward dipping clinothemes is recorded in
outcrop sections that are sub-parallel to the depositional
dip (SSE) (Fig. 4 d). Here, beds can be traced downwards
to a position where they tangentially meet the lower
boundary, at which point the bed thickness is zero. These
pinch-outs appear as thin sandstone wedges protruding
into the FA2 mudstone below. Correspondingly, mudstone drapes mark the boundaries between individual
clinothemes with a maximum thickness at the base (2-3
cm) and tapering upwards into a single mud drape horizon, generally within less than 2 m. Up to 50 cm thick
mudstone beds separate clinothemes at a few places. Burrows of unidentified type are recorded in places at the
lower boundary of FA4.
Upward coarsening motifs characterize the FA4 deposits exposed along outcrops orientated as vertical sections
perpendicular or sub-perpendicular to the depositional
dip. Coal beds (5 cm thick) along with plant fragments
mark sandstone bed boundaries in the upper 2 m of FA4.
Ornithopod dinosaur tracks (Pers. comm. J. H. Hurum,
Natural History Museum, University of Oslo, Norway)
embedded in Facies J were discovered in Hanaskogdalen,
near the top of FA4. Planolites and Anchorichnus (?) burrows are observed on Facies H bed surfaces.
At the Konusen locality (Fig. 1), relatively thin (maximum 30-50 cm thick) sandstone beds of Facies G, H, I
and J appear roughly in the middle of FA2, preceded and
succeeded by 5-10 m of mudstone. The total thickness is
about 2 m in the western Sassenfjorden area, and pinches
out to the west of Criocerasaksla. The upper boundary of FA4 is a conformable transition into FA5, and is
described further below.
Interpretation
The deposits described above are interpreted as representing a prograding delta lobe, as illustrated in Fig. 75, in accordance with the delta lobe interpretation illus-
NORWEGIAN JOURNAL OF GEOLOGY
trated in Fig. 11, p. 581 in Gjelberg & Steel (1995).The
basinward dipping clinothemes and sandstone pinchout geometries reflect sandstone deposition into standing water. The presence of coal seams and dinosaur
footprints indicate deposition of the beds in which they
occur as subaerial or in very shallow water coastal environments. This suggests they were formed in the most
proximal part of the delta, as topset deposits. At present, it is even possible that the bioturbation occurring in
these is of lacustrine origin. Palaeowater depth did probably not exceed 9 m (the maximum sandstone thickness)
for this facies association. The mud drapes on each clinotheme unit may reflect tidal influence during deposition. Restricted, shallow bays, as is suggested for FA2,
are prone to amplify tidal currents, hence increasing the
probability of a tidal modulation of the prograding delta
lobe geometry and facies. The laterally extensive deltaic
sandstone bodies suggest the delta lobes developed as
elongated features extending into the basin, as seen in
modern “bird-foot” deltas, an interpretation supported
by Steel (1977).
FA5 Coastal floodplain
Description
FA5 is largely dominated by Facies K (mudstone), but
also includes Facies E (massive structureless sandstone),
G (asymmetrical ripple laminated sandstone), H (symmetrical ripple-laminated sandstone), I (plane-parallel
laminated silt- and sandstone), J (interbedded sandstone
and mudstone) and L (coal) (Tables 1 and 2). The lower
boundary towards FA4 is conformable, and the absence
of basinward dipping clinothemes and increased internal
heterogeneity are the main features that distinguish FA5
from the delta top deposits (FA4). The upper boundary of FA5 is marked either by an erosive contact to an
overlying fluvial channel, or as a conformable transition
into overlying open marine deposits. This conformable
boundary is generally a mudstone to mudstone contact,
and is by nature difficult to pinpoint. The upper, fine
grained sediments of the Helvetiafjellet Formation are
commonly covered by talus, which is a further complicating factor in determining the exact position of this
boundary. FA5 is characterized by mudstone and coal
intervals with rootlet horizons and desiccation cracks,
plant fragments and palaeocurrent directions with no
apparent directional trend. Sandstone beds of facies E,
G and H range from 0.1 to 2 m in thickness (Fig. 4 e),
with both erosive and non-erosive lower boundaries, and
can be traced up to 150 m laterally. Sandstone facies I, J
and L occur randomly within this stratigraphic unit, and
cannot as a rule be traced laterally beyond a few meters.
FA5 units on the whole are generally laterally persistent
beyond the outcrop limits in Nordenskiöld Land, and
occur at several stratigraphic levels, separated by FA6
(described below) (Figs 5 and 6). Intervals which are
obscured by talus are inferred to consist of fine grained
mudstone. No further details are forthcoming.
NORWEGIAN JOURNAL OF GEOLOGY
Interpretation
FA5 strata are interpreted to have formed on a coastal
floodplain, laterally adjacent to the main sediment transport channels (Fig 6-5). It is suggested here that they have
conformably succeeded fluvial channels (in the case of
lateral migration and abandonment) and delta top environments (in the case of progradation), as has also been
discussed by Gjelberg & Steel (1995). As a result of further, renewed lateral migration on the coastal plain, fluvial (and distributary-) channels eroded the upper part
of these deposits before depositing fluvial channel sediments. This is a highly dynamic, and thus varied, depositional environment characterized by pools of standing water, vegetation growth, creeks, crevasse splays and
channels, and wet marshes. Low-gradient coastal plain
environments are easily flooded, and basinward of the
bay-line position (cf. Posamentier & Vail 1988), the plain
may be intermittently affected by spring tides or storm
surges. It is thus possible that a portion of the mudstone
content in FA5 may be marine or brackish in origin, and
possibly a tidal flat during the final stages of its development.
FA6 Fluvial channel
Description
Several 2-10 m thick, very clean sandstone units composed of Facies B (trough cross-stratified sandstone),
C (tabular cross-stratified sandstone), D (plane parallel stratified sandstone), E (massive structureless sandstone) and M (cross-stratified sandstone with double
mud drapes) comprise FA6 (Table 1). FA6 units occur at
several stratigraphic levels in the upper part of the Helvetiafjellet Formation in Nordenskiöld Land; their distribution is shown in Figs. 5 and 6. The lowest unit is the
most laterally extensive, extending beyond the outcrop
area included in this study. Above this unit, in the Sassenfjorden section, one or both lateral terminations of
individual FA6 units are recorded within the study area.
In the significantly shorter Hanaskogdalen section, all of
the FA6 units extend beyond the outcrop area.
The lower part of the FA6 units displays a similar internal organization as FA1, being mainly composed of
trough cross-stratified sandstone, but without extrabasinal conglomerate clasts. The lowest order of internal
surfaces described in FA1 is also observed within FA6,
separating individual bar forms up to 3 m in thickness.
The bar-bounding surfaces are less clearly defined compared to FA1. The lower boundaries of FA6 units are
generally abrupt, with an erosive contact to underlying coastal floodplain deposits (Fig. 4 f). Palaeocurrent
directions are consistent with FA1, having a mean direction of roughly 138˚ (Fig. 1). Facies M is only recorded in
the highest stratigraphic levels of FA6 in Hanaskogdalen.
These observations are made on very poor outcrops, and
can thus not be confidently placed on a log trace. Correlation and stratigraphic context for the highest FA6 units
Paralic sedimentation on an epicontinental ramp shelf 351
in both Hanaskogdalen and Sassenfjorden are problematic due to deteriorating outcrop quality with increasing
stratigraphic height, and a reduction of FA6 unit thicknesses.
Interpretation
FA6 is interpreted to have been formed as fluvial channel
infill sediments. The basal erosive boundaries and high
energy facies assemblage reflect channelized transport of
sand across the FA5 coastal plain (Fig. 7-6). The transport direction was to the SSE, suggesting that the palaeocoastline was oriented roughly WSW-NNE during this
phase of development and largely unaltered since deposition of FA1. The apparent lenticular shape of the upper
fluvial channel sandstone units, seen in sections oriented
semi-perpendicularly to the regional palaeocurrent
direction (Sassenfjorden, Fig. 5), may imply that these
sandstone bodies represent narrow distributary fluvial
channels on a distal part of the coastal plain. The double
mud drapes recorded in the upper stratigraphic levels of
FA 6 reflect tidal influence with an increase in current
energy, possibly heralding the transgressive event that
followed. The abrupt upper boundary of FA 6 may be
the result of a rapid rise in relative sea-level, a local shift
in depositional environment, or a combination of both
factors. This upper boundary is identified as a flooding
surface, as it marks an abrupt lithological change, but the
palaeo-water depths above this boundary have not been
estimated using biostratigraphic methods. Hence, the
flooding surface is in reality the only identifiable surface
within a flooding interval that is probably represented by
a few metres (?3-10 m) of siltstone and mudstone.
FA7 Marine shelf
Description
The Rurikfjellet Formation and the Carolinefjellet Formation, located respectively below and above the Helvetiafjellet Formation, are here both included in FA7, based
on their mudstone dominated lithological composition,
and because they represent the adjacent formations
of the study object (Fig. 4 g). The main facies in FA7 is
Facies K (mudstone), but Facies E (massive structureless
sandstone), F (hummocky cross-stratified sandstone), G
(asymmetrical ripple- laminated sandstone) and I (planeparallel laminated silt and sandstone) are also recorded
in laterally extensive beds up to 1 m in thickness (Tables
1 and 2). The sandstone beds contain more mud than the
previously described sandstone facies, and are greyish
brown in colour. Bioturbation is common and the burrows Skolithos and Diplocraterion are recorded in Facies E
and G. The Rurikfjellet Formation is part of an up to 400
m thick mudstone succession (Fig. 2). Several upward
coarsening shale-sandstone successions are recorded
in the upper part of this formation which terminates at
the erosional regional unconformity mentioned above,
beneath the Helvetiafjellet Formation.
352 I. Midtkandal et al.
NORWEGIAN JOURNAL OF GEOLOGY
Table 2. Facies associations recorded in Nordenskiöld Land.
Formation
Member
Carolinefjellet Formation
Helvetiafjellet Formation
Mid- to upper
Helvetiafjellet
Formation
Festningen sandstone member
Rurikfjellet Formation
Architectural
element
Depositional
Environment
Facies included
(table 1)
Sequence stratigraphic surface
FA 7
Marine shelf
K, E, F, G, I
FS 2
FA 6
Fluvial channel
B, C, D, E
FA 5
Coastal floodplain
K, E, G, H, I, J, L
FA 4
Delta lobe front
and top
C, D, E, G, H, I, J,
K, L
FA 3
Delta lobe toeset
D, J
FA 2
Interdistributary
bay or lagoon
K, G, H, I, J
FA 1
Braided fluvial
channel belt
A, B, C, D, E
FS 1
FA 7
Marine shelf
K, E, F, G, I
SB
The Carolinefjellet Formation is an up to ?1200 m thick
mudstone succession with a varying number of sandstone beds (Parker 1967; Nagy 1970) (Fig. 2). Its lower
boundary is conformable with the upper parts of coastal
plain mudstone units of the Helvetiafjellet Formation,
and is thus difficult to define where the exposures are
poor.
Forkastningsfjellet
Janusfjellet
2500 m
W
Interpretation
The Rurikfjellet Formation was deposited as a regressive, upward shallowing shelf succession on the Boreal
epicontinental shelf of Spitsbergen (Dypvik 1985; Mørk
et al. 1999). The Carolinefjellet Formation, capping the
Helvetiafjellet Formation, was formed in response to the
transgression that finally terminated the paralic depositional environment of the Helvetiafjellet Formation
(Nagy 1970).
Konusen W Konusen E
1000 m
600 m
Criocerasaksla
1100 m
Wimanfjellet
2300 m
Coastal plain mudstone
palaeocurrent
direction
Fluvial channel sandstone
10 m
1 Km
Dinosaur
footprint
Delta sandstone
Paralic sandstone
Restricted marine mudstone
Shallow marine sandstone
FS2
E
Open marine mudstone
C
7
plant fossil
coal bed
bioturbation
FS2
6
5
4
FS1
FS1
3
SB
SB
2
1
Fig. 5. Correlation panel from the southern shore of Sassenfjorden. The numbered stratigraphic intervals on the right correspond to the depositional environments in Fig. 7.
NORWEGIAN JOURNAL OF GEOLOGY
Log correlation
Sedimentological log traces were recorded at a total of 11
localities; 5 in Hanaskogdalen, and 6 along the southern
shore of Sassenfjorden. A correlation panel has been constructed for each of the two main semi-continuous cliff
sections, using identifiable sediment bounding surfaces
acting as links between log traces (Figs. 5 and 6).
Across the entire outcrop area in Nordenskiöld Land,
the lower boundary of the Helvetiafjellet Formation is
an unconformity due to erosion(Fig. 4 g). As described
above, it marks an abrupt shift from a marine shelf
environment (FA 7) into a fluvial channel environment
(FA1). As one of the most recognizable sequence stratigraphic surfaces within the Helvetiafjellet Formation,
it is nevertheless a diachronous surface, and is thus not
used as the main datum plane for log correlation in this
study. The upper boundary of the Helvetiafjellet Formation is not easily identifiable in the field, and it is consequently impractical to use it as a chronostratigraphical or
lithostratigraphical correlation surface.
The flooding surface that marks the upper boundary of
FA 1 (FS1, Table 1), is used as the main datum plane, as
it represents a practically isochronous surface with only
an insignificant amount of associated topographic relief.
Correlation between the panels of two cliff sections
Hanaskog 3 West
Paralic sedimentation on an epicontinental ramp shelf 353
involves greater uncertainties, partly because of the significantly shorter cliff section along the northern side of
Hanaskogdalen (1500 m) compared to the section along
the southern shore of Sassenfjorden (7000 m). Thus,
three-dimensional control of the depositional environments that developed in the area is somewhat limited,
but can be inferred within reason. Figures 5 and 6 show
the constructed correlation panels for the Sassenfjorden
and Hanaskogdalen cliff sections, respectively. Notice the
difference in scale between the two panels.
Discussion
Development of depositional environments
Fall in relative sea-level; development of a regional sequence boundary
Open marine shelf conditions prevailed during deposition of the Rurikfjellet Formation (Edwards 1976;
Dypvik 1980; Dypvik 1985; Mørk et al. 1999; Århus
1991) (Fig. 7-1). Upward coarsening successions in the
upper part of the Rurikfjellet Formation reflect a regressive and shallowing shelf. Forced regressive features, such
as detached shorelines or sharp-based shoreline successions are not documented at the boundary between the
Rurikfjellet and Helvetiafjellet formations in Nordenskiöld Land or anywhere else in Spitsbergen, suggesting
Hanaskogdalen 1 West
W
Hanaskogdalen 2 West
Hanaskogdalen 1 East
Hanaskogdalen 2 East
E
7
FS2
6
C
5
4
FS1
3
SB
5m
100 m
1
2
Fig. 6. Correlation panel from Hanaskogdalen. Notice the difference in scale compared to Fig. 5. See figure 5 for legend. The numbered
stratigraphic intervals on the right correspond to the depositional environments in Fig. 7.
354 I. Midtkandal et al.
NORWEGIAN JOURNAL OF GEOLOGY
Aggradation of paralic environments:
7: Flooding stage
6
4-6: Aggadational
paralic stage
5
3: Earliest rise in
relative sea-level
4
2: Erosional stage
1: Upper Rurikfjellet
Formation
that the regression marked by the boundary between
these two formations was non-accretionary (cf. HellandHansen & Gjelberg 1994). Tectonic uplift to the northwest caused a fall in relative sea-level across an area larger
than the gross outcrop area on Spitsbergen (Nøttvedt et
al. 1992). During this regional fall in relative sea-level,
an unknown amount of the Rurikfjellet Formation was
eroded as denudation patterns were established (Fig. 72). The erosion resulted in a palaeotopography of moderate relief, truncating the Rurikfjellet Formation (Figs.
5 and 6) variably.
Early rise in relative sea-level; deposition of a fluvial braidplain
Deposition of the Helvetiafjellet Formation commenced
at the onset of a rise in relative sea-level that led to base
level elevation and the generation of accommodation
space. Facies association 1 (FA1) is the stratigraphically
lowest depositional unit in the Helvetiafjellet Formation,
Fig. 7. Successive development of depositional environments
in the Nördenskiold Land area. The numbered timeslices
correspond to the stratigraphic intervals marked in Figs. 5
and 6 and illustrate a possible depositional scenario for the
different stages of Helvetiafjellet Formation development.
See discussion in text for details.
and represents a widespread system of braided fluvial
channel infill (Fig. 7-3), lithostratigraphically termed
the Festningen sandstone member (Mørk et al. 1999). At
the onset of the rise in relative sea-level, vertical accommodation space was limited, causing the braided stream
channels to migrate laterally during frequent avulsions,
thus forming a sheet-like, multilateral sandstone body.
Consequently, the entire emerged shelf area was filled
with braidplain sand. High channel mobility and erosive
capacity removed any fine-grained overbank facies, and
major underlying irregularities were smoothed out as the
fluvial channel courses were continuously re-directed in
search of steeper gradients, as described for this type of
depositional setting by Holbrook (1996). The result was
a laterally persistent, high net/gross sandstone body with
limited thickness variations.
The fluvial sandstone blanket was likely deposited in a
backstepping way in response to rising sea-level and base
level, as also suggested by Gjelberg and Steel (1995). The
NORWEGIAN JOURNAL OF GEOLOGY
Festningen sandstone member is thus a typical diachronous depositional unit. However, the lateral extent of the
fluvial sandstone is remarkable, and the backstepping
mode may have been very rapid, with numerous bypass
surfaces contained within the unit. The river systems on
the emerged shelf may have acted as important routes for
sediment transport, depositing fine grained components
in the deeper part of the epicontinental basin in the adjacent Barents Sea region to the southeast. In this part of
the basin, a shelf edge may have developed, but this has
not yet been recognized in any Spitsbergen outcrop.
Continued rise in relative sea-level; aggradation of coastal
plain environments
The entire Nordenskiöld Land area was flooded after
deposition of the Festningen sandstone member and the
upper part of the Helvetiafjellet Formation, previously
named the Glitrefjellet Member (Parker 1967; Mørk et al.
1999), was deposited. The stratigraphic interval is characterized by its heterolithic composition and frequent
facies changes. The flooding was caused by increase in
the rate of relative sea-level rise, a reduction in the rate of
sediment supply, or a combination of the two. Restricted
shallow marine conditions were established, such as
interdistributary bays and lagoons in a setting where
small, continuously changing deltas developed along the
shoreline. Infrequent sandstone intercalations within
the mudstone-dominated succession reflect pulses of
increased sediment supply. The delta toe sand beds (FA3)
that prograded from the west into the otherwise muddominated depositional environment (Fig. 7-4) indicate
an approaching palaeo-shoreline located somewhere
to the west of Nordenskiöld Land, here inferred to have
been oriented roughly NNE-SSW, judging from palaeocurrent data that show dominant flow towards the SSE,
and sandstone pinch-out directions towards the east or
southeast.
The deltaic deposits that succeed FA3 reflect a renewed
shoreline progradation in this part of the basin (Fig. 75). The deltaic environment was modified by tidal and
wave currents. Continued regression shifted the shoreline further to the southeast, establishing coastal plain
conditions in Nordenskiöld Land (FA5). This terrestrial
environment was characterized by relatively shallow
and narrow distributary rivers dissecting a wet, marineinfluenced coastal floodplain, where organic matter and
fine-grained overbank sediments accumulated (Fig. 7-6).
The final stages of fluvial deposition in the area became
increasingly influenced by tidal currents as the rise in relative sea-level increased.
Increased rate of rise in relative sea-level; transgression of
the coastal plain
As the rate of rise in relative sea-level increased, a transgression flooded the entire area (forming FS2), initiating
Paralic sedimentation on an epicontinental ramp shelf 355
deposition of the Carolinefjellet Formation, as is reflected
in the succession that represents the transition from
coastal plain to shallow marine conditions. The depositional environment returned to a progressively deepening, open marine shelf condition (Fig. 7-7), the transgression culminating in the deposition of fine-grained
sediments represented by the Inkjegla Member of this
formation (Parker 1967; Nagy 1970).
Basin physiography as a factor of depositional control
The epicontinental Boreal basin had a very low depositional gradient, as is reflected in the predominantly mudstone deposits contained within the Rurikfjellet Formation. Gjelberg & Steel (1995) estimated the gradient to
have been about 0.09˚ in the Spitsbergen domain during deposition of the Helvetiafjellet Formation. Despite
the very low-gradient depositional dip, river competency during lowstand was sufficient to transport extrabasinal clasts up to 10 cm in diameter into the basin in
Nordenskiöld Land, a minimum distance of 60 km from
the hinterland in the west or northwest. In this setting,
without a marked gradient increase represented by a
shelf break, a significant fall in relative sea-level simply
resulted in a repositioning of the facies belts in relation
to the new shoreline position. Depending on the gradient and elevation of a basin’s equilibrium profile, sediments may or may not accumulate during forced regression (Helland-Hansen & Martinsen 1996; Posamentier
2001). Independently of whether forced regressive sediments accumulated or not, the basin floor gradient was
the most important factor in determining distance and
rate of regression; the slope gradient controls how far
into the basin the shoreline is shifted following a fall in
relative sea-level (Posamentier & Morris 2000). The Helvetiafjellet Formation shoreline was shifted to a position
southeast of present day Spitsbergen, without experiencing any abrupt increase in basin floor gradient.
On an emerged shelf, river incision takes place in
response to increase in slope gradient relative to the fluvial equilibrium profile, along which the river path develops during a fall in relative sea-level (Schumm 1993). If
the sea-level remains above a shelf edge, the gradient of
the shelf must be greater than that of the coastal plain
for incision to take place (Talling 1998). Rivers may not
incise at all if they enter a broad, low-angle shelf which
is merely an extension of the equilibrium profile of the
alluvial and coastal plains (Woolfe et al. 1998).
Because of the factors discussed above, it is suggested
here that distinct incised valleys may have formed during the erosion of the upper Rurikfjellet Formation in
areas upstream of Nordenskiöld Land, where the depositional gradient is believed to have been steeper, as also
suggested by Nøttvedt et al. (1992), Gjelberg & Steel
(1995) and Midtkandal et al. (in review). The incised valleys widened down-slope to the southeast and coalesced
356 I. Midtkandal et al.
into a broad erosional plain, where several kilometres of
broad, shallow stretches were bypassed by fluvial systems.
This plain of fluvial entrenchment is thought to have
formed an incised valley complex, several hundred of
kilometres wide, like that delineated by the Pleistocene
maximum sea-level fall in the East China Sea (Wellner &
Bartek 2003).
NORWEGIAN JOURNAL OF GEOLOGY
Depositional
environment
<1
Carolinefjellet
Fm
Lateral and downstream facies changes during intervals
between high-frequent changes in relative sea-level are
suggested to be the result of highly dynamic autogenic
sediment dispersal processes. Limited vertical accommodation space coupled with a high clastic input to the
coastal areas gave rise to frequent avulsions (cf. Jones &
Schumm 1999), which in turn altered the positioning of
local depocentres. Combined with irregular coastal morphology and variations in wave and tidal energy, highly
heterogenic and irregular sediment stacking patterns
developed.
The LIP-volcanism in the Boreal realm and sill emplacements in eastern Spitsbergen may have influenced depositional processes and the resulting stacking patterns
tectonically (Midtkandal et al. in review). No faults that
might have been related to Early Cretaceous tectonics
and volcanism have been recorded within the Nordenskiöld Land area; however, the influence of such allogenic
factors on sedimentation patterns can not be dismissed
for the Nordenskiöld Land area either.
The depositional model of Gjelberg & Steel (1995) for
the Helvetiafjellet Formation within the Spitsbergen
domain of the Boreal basin suggests retrogradation of
1
>1
Retrogradation/
progradation
open marine
FS2
?
coastal
plain
Paralic sedimentation on a low-gradient
shelf ramp: critical variables
Aggradation/
retrogradation
?
Helvetiafjellet Fm
Paralic environments are generally highly susceptible to
any changes in factors controlling depositional facies and
sandstone body architecture (e.g. Emery & Myers, 1996).
The transgressive systems tract is in the present Nordenskiöld Land example, characterised by an overall
aggradational stacking pattern of paralic sediments, thus
showing that the rate of sediment supply closely matched
the rate of increase in accommodation space during this
time interval (Fig. 8). Low-amplitude, high-frequency
changes in relative sea-level would, in such a very lowsloping ramp shelf setting, cause very rapid and laterally
extensive facies changes during a rise, as well as during
a fall in sea-level. The mechanisms that controlled facies
changes within the upper, heterolithic part of the Helvetiafjellet Formation in Nordenskiöld Land may have been
avulsion events or high-frequency sea-level changes. This
is interpreted as a type of accretionary transgressive systems tract, a depositional setting that according to Helland-Hansen & Gjelberg (1994, p. 43) requires “a subtle
balance between rate of sediment supply and rate of sealevel rise”.
Architectural
style
A/S
delta
progradation
Progradation
FS1
braidplain
Rurikfjellet
Fm
Aggradation
SB
open marine
Aggradation
Fig. 8. Outline of architectural trends linked to the A/S ratio during
deposition of the Helvetiafjellet Formation in Nordenskiold Land.
The low-frequency, high amplitude A/S trends are relatively clear
compared to the high- frequency, low amplitude variations. The
interplay between allogenic and autogenic factors is the main source
of uncertainty.
the shoreline towards the northwest, as a response to
transgression, intermittently broken and reset by highfrequent, low-amplitude changes in sea-level. Their
model includes fluvial sandstone wedges linked to the
basal Festningen sandstone member, formed in response
to repeated high-frequent falls in sea-level. The present
data set does not support this model for Spitsbergen, as
shown by the overall aggradational architectural style of
paralic facies associations in the upper part of the Helvetiafjellet Formation. Though the present model for the
Helvetiafjellet Formation outcrops approaches the old
“layer-cake model” reviewed by Gjelberg & Steel (1995),
it is founded on the dynamic behaviour of a very lowsloping shelf, and sequence stratigraphical principles of
aggrading facies belt associations during the fall and rise
in relative sea-level. Conclusions
• The Barremian Helvetiafjellet Formation in Nordenskiöld Land, Spitsbergen, reveals an internal stratigraphy and facies distribution formed in response to a full
cycle of fall and rise in sea-level on a very low-gradient
ramp shelf of the Boreal epicontinental basin.
• During a fall in sea-level fluvial erosion took place,
NORWEGIAN JOURNAL OF GEOLOGY
truncating the emerged shelf succession forming the
top of the open-marine Rurikfjellet Formation, and
possibly forming incised valleys in the proximal parts
of the emerged shelf. A wide plain of fluvial scouring
in its distal part, may be part of a very broad incised
valley complex.
• The basal, subaerially formed sequence boundary acted
as a bypass surface for fluvial coarse-clastic sediment
transport during lowstand, in accordance with the
opinion that fluvial systems on low-gradient emerged
shelves have the capacity and competency to transport
large sand volumes into the deeper part of epicontinental basins.
• Due to the early rise in sea-level, fluvial sediments
started to accumulate in a backstepping pattern, leaving behind a sheet-like fluvial sandstone body covering
the whole sequence boundary.
• A transgressive systems tract, in the middle and upper
parts of the Helvetiafjellet Formation, developed with
a dominantly aggradational stacking pattern of paralic
facies associations, including restricted bay, delta lobes,
lagoons, distributary rivers and coastal plain deposits.
The aggradational style was controlled by an overall
balance between rate of accommodation versus rate of
sediment influx, minor high-frequent sea-level fluctuations as well as autogenic variables such as differential
compaction, stream and delta lobe avulsions, and a
dynamically changing coastal morphology.
• An apparent “layer-cake” stratigraphy with very gently sloping shelf ramps is the result of rapid and lateral
changes in facies belt positions, brought about by moderate, high-frequent fluctuations in relative sea-level,
combined with variations in factors such as A/S, differential subsidence, delta lobe shifts and river avulsion.
Acknowledgement: The authors thank Atle Mørk and Paul Atle Midtkandal for insightful comments and reviews. Reviews by Tine Lærdal
and Morten Smelror, appointed by the Norwegian Journal of Geology,
were very helpful in improving the clarity and contents of the manuscript. The University Centre of Svalbard (UNIS) is gratefully acknowledged for generous support in preparations for field work. Espen Tallaksen is also thanked for field assistance.
References
Ahokas, J.M., Midtkandal, I. & Nystuen, J.P., 2005. Depositional environment, processes and sequence stratigraphy of the paralic Helvetiafjellet Formation in Ullaberget, Southern Spitsbergen. In:
Nakrem, H.A. (ed.): Abstracts and Proceedings of the Geological
Society of Norway, 1.
Allen, P.A. & Allen, J.R., 2005. Basin Analysis: Principles and Applications. Blackwell Publishing, Oxford, 549 pp.
Alve, E., 1990. Variations in estuarine foraminiferal biofacies with
diminishing oxygen conditions in Drammensfjord, SE Norway. In:
Hemleben, C., Kaminski, M.A., Kuhnt, W. and Scott, D.B. (eds.):
Palaeoecology, Biostratigraphy, Palaeoceanography, and Taxonomy of
Agglutinated Foraminifera, 661-694. Kluwer Academic Publishers,
Dordrecht.
Birkenmajer, K., 1975. Jurassic and Lower Cretaceous sedimentary formations of SW Torell Land, Spitsbergen. Studia Geologica Polonika,
44, 7-43.
Paralic sedimentation on an epicontinental ramp shelf 357
Busas, M.A., 1974. Vertical distribution of Ammobaculites in the
Rhode River, Maryland. Journal of Foraminiferal Reseach, 4, 144147.
Carey, J.S., Swift, D.J.P., Steckler, M., Reed, C.R. & Niedoroda, A.W.,
1999. High-resolution sequence stratigraphic modeling 2: Effects
of sedimentation processes. In: Harbaugh, J.W., Watney, W.L., Rankey, E.C., Slingerland, R., Goldstein, R.H. and Franseen, E.K. (eds.):
Numerical Experiments in Stratigraphy: Recent Advances in Stratigraphic and Sedimentologic Computer Simulations, 151-164. SEPM
Special Publication 62.
Dypvik, H., 1980. The sedimentology of the Janusfjellet Formation,
central Spitsbergen (Sassenfjorden and Agardhfjellet areas). Norsk
Polarinstitutt Skrifter, 172, 97-134.
Dypvik, H., 1985. Jurassic and Cretaceous black shales of the Janusfjellet Formation, Svalbard, Norway. In: Hesse, R. (ed.): Sedimentology
of siltstone and mudstone, 235-248. Sedimentary Geology.
Dypvik, H., Nagy, J., Eikeland, T.A., Backer, O.K. & Johansen, H., 1991.
Depositional conditions of the Bathonian to Hauterivian Janusfjellet Subgroup, Spitsbergen. Sedimentary Geology, 72(1-2), 55-78.
Edwards, M.B., 1976. Depositional environments in Lower Cretaceous
regressive sediments, Kikutodden, Sørkapp Land, Svalbard. Norsk
Polarinstitutt Årbok 1974, 35-50.
Edwards, M.B., 1978. A regional survey of composition, provenance
and diagenesis of sandstones in the Lower Cretaceous Helvetiafjellet Formation, Svalbard. Norsk Polarinstitutt Årbok 1977, 343-345.
Edwards, M.B., 1979. Sandstone in Lower Cretaceous Helvetiafjellet
Formation, Svalbard: Bearing on Reservoir Potential of Barents
Shelf. American Association of Petroleum Geologists Bulletin, 63(12),
2193-2203.
Edwards, M.B., Bjaerke, T., Nagy, J., Winsnes, T.S. & Worsley, D., 1979.
Mesozoic stratigraphy of eastern Svalbard; a discussion. Geological
Magazine, 116(1), 49-54.
Emery, D. & Myers, K. (eds.): 1996. Sequence stratigraphy. Blackwell
Science, London, United Kingdom, 297.
Fagherazzi, S., Howard, A.D. & Wiberg, P.L., 2004. Modeling fluvial
erosion and deposition on continental shelves during sea level
cycles. Journal of Geophysical Research, 109(F03010), doi:10.1029/
2003JF000091.
Fischer, A.G., 1981. Climatic oscillations in the biosphere. In: Nitecki,
M.H. (ed.): Biotic Crises in Ecological and Evolutionary Time, 103131. Academic Press, New York.
Gjelberg, J. & Steel, R., 1995. Helvetiafjellet Formation (BarremianAptian), Spitsbergen: characteristics of a transgressive succession.
In: Steel, R., Felt, V.L., Johannesen, E.P. and Mathieu, C. (eds.):
Sequence Stratigraphy on the Northwest European Margin, 571-573.
Norwegian Petroleum Society (NPF). Special Publication 5.
Grocke, D.R., Price, G.D., Ruffell, A.H., Mutterlose, J. & Baraboshkin,
E., 2003. Isotopic evidence for Late Jurassic-Early Cretaceous climate change. Palaeogeography, Palaeoclimatology, Palaeoecology,
202(1), 97-118.
Grosfjeld, K., 1992. Palynological age constraints on the base of the
Helvetiafjellet Formation (Barremian) on Spitsbergen. Polar Research, 11(1), 11-19.
Harland, W.B., Gaskell, B.A., Heaffard, A.P., Lind, E.K. & Perkins, P.J.,
1984. Outline of Arctic post-Silurian continental displacements:
Petroleum geology of the North European margin, 137-48. Graham
and Trotman, London, United Kingdom.
Helland-Hansen, W. & Gjelberg, J.G., 1994. Conceptual basis and variability in sequence stratigraphy: a different perspective. Sedimentary Geology, 92(1-2), 31-52.
Helland-Hansen, W. & Martinsen, O.J., 1996. Shoreline trajectories
and sequences; description of variable depositional-dip scenarios.
Journal of Sedimentary Research, 66(4), 670-688.
Holbrook, J.M., 1996. Complex fluvial response to low gradients at
maximum regression: a genetic link between smooth sequenceboundary morphology and architecture of overlying sheet sandstone. Journal of Sedimentary Research, 66(4), 713-722.
Hurum, J.H., Milàn, J., Hammer, Ø., Midtkandal, I., Amundsen, H.
358 I. Midtkandal et al.
& Sæther, B., 2006. Tracking polar dinosaurs - new finds from the
Lower Cretaceous of Svalbard. Norwegian Journal of Geology, 86,
397-402.
Jones, L.S. & Schumm, S.A., 1999. Causes of avulsion: an overview.
Fluvial Sedimentology VI: International Association of Sedimentologists, Special Publication, 28, 171-178.
Maher, H.D., Hays, T., Shuster, R. & Mutrux, J., 2002. Signature of a
mafic volcanic source in Barremian to Albian sandstones on Spitsbergen, Norway: Geological Society of America, 2002 annual meeting, 208. Geological Society of America (GSA), Boulder, CO, United States.
Maher, H.D., Jr., 1999. Character of Cretaceous High Arctic LIP from
a Svalbard perspective: Geological Society of America, 1999 annual
meeting, 430. Geological Society of America (GSA), Boulder, CO,
United States.
Maher, H.D., Jr., Hays, T., Shuster, R. & Mutrux, J., 2004. Petrography
of Lower Cretaceous sandstones on Spitsbergen. Polar Research,
23(2), 147-165.
Miall, A.D., 1988. Reservoir heterogeneities in fluvial sandstones: lessons from outcrop studies. American Association of Petroleum Geologists Bulletin, 72(6), 682-697.
Midtkandal, I., 2002. Depositional environment, sandstone architecture and sequence stratigraphy of the lower Cretaceous Helvetiafjellet Formation, Spitsbergen. Cand. Scient. Thesis, University of
Oslo, Norway, 162.
Midtkandal, I., Ahokas, J. & Nystuen, J.P., 2005. The lower Cretaceous Helvetiafjellet Formation, Spitsbergen: paralic environment
at a ramp shelf from falling to rising sea level: Vinterkonferansen.
Geological Society of Norway (NGF), Abstracts and Proceedings,
Røros, Norway, 74-75.
Miloslavskij, M.J., Birjukov, A.S., Slenskij, S.N., Hansen, S., Larsen,
B.T., Dallmann, W.K. & Andresen, A., 1992. Agardhfjellet, Geological map, Svalbard, sheet D9G. Norsk Polarinstitutt.
Murray, J.W., 1991. Ecology and Palaeoecology of Benthic Foraminifera. Longman Scientific and Technical, London, 329 pp.
Mørk, A., Dallmann, W.K., Dypvik, H., Johannesen, E.P., Larssen, G.B.,
Nagy, J., Nøttvedt, A., Olaussen, S., Pchelina, T.M. & Worsley, D.,
1999. Mesozoic lithostratigraphy. In: Dallmann, W.K. (ed.): Lithostratigraphic lexicon of Svalbard, Review and recommendations for
nomenclature use. Upper Palaeozoic to Quaternary bedrock, 127-214.
Norsk Polarinstitutt, Tromsø.
Nagy, J., 1970. Ammonite faunas and stratigraphy of Lower Cretaceous
(Albian) rocks in southern Spitsbergen. Norsk Polarinstitutt Skrifter,
1 - 58.
Nagy, J., Pilskog, B. & Wilhelmsen, R.M., 1990. Facies controlled distribution of foraminifera in the Jurassic of the North Sea Basin. In:
Hemleben, C., Kaminski, M.A., Kuhnt, W. and Scott, D.B. (eds.):
Paleoecology, Biostratigraphy, Paleoceanography and Taxonomy of
Agglutinated Foraminifera, 621-657. Kluwer Academic Publishers,
Dordrecht.
Nagy, J. & Seidenkrantz, M.S., 2003. New foraminiferal taxa and revised biostratigraphy of Jurassic marginal marine deposits on Anholt,
Denmark. Micropaleontology, 49(1), 27-46.
Nagy, J., 2005. Delta-influenced foraminiferal facies and sequence
stratigraphy of Paleocene deposits in Spitsbergen. Palaeogeography,
Palaeoclimatology, Palaeoecology, 222, 161-179.
Nemec, W., Steel, R.J., Gjelberg, J., Collinson, J.D., Prestholm, E. &
Øxnevad, I.E., 1988a. Anatomy of Collapsed and Re-established
Delta Front in Lower Cretaceous of Eastern Spitsbergen: Gravitational Sliding and Sedimentation Processes. American Association
of Petroleum Geologists Bulletin, 72(4), 454 - 476.
Nemec, W., Steel, R.J., Gjelberg, J., Collinson, J.D., Prestholm, E., Øxnevad, I.E. & Worsley, D., 1988b. Exhumed rotational slides and scar
infill features in a Cretaceous delta front, eastern Spitsbergen. Polar
Research, 6, 105-112.
Nemec, W., 1992. Depositional controls on plant growth and peat
accumulation in a braidplain delta environment: Helvetiafjellet Formation (Barremian - Aptian), Svalbard. In: McCabe, P.J.
NORWEGIAN JOURNAL OF GEOLOGY
and Parrish, J.T. (eds.): Controls on the Distribution and Quality of
Cretaceous Coals, 209-226. Boulder, Colorado. Geological Society
of America Special Paper 267.
Nøttvedt, A., Livbjerg, F., Midtbøe, P.S. & Rasmussen, E., 1992. Hydrocarbon potential of the Central Spitsbergen Basin. In: Vorren, T.O.,
Bergsager, E., Dahl-Stamnes, Ø.A., Holter, E., Johansen, B., Lie, E.
and Lund, T.B. (eds.): Arctic Geology and Petroleum Potential, 333361. Norwegian Petroleum Society (NPF) Special Publication.
Parker, J.R., 1967. The Jurassic and Cretaceous sequence in Spitsbergen. Geological Magazine, 104(5), 487-505.
Posamentier, H.W. & Vail, P.R., 1988. Eustatic controls on clastic deposition II-Sequence and systems tract models. In: Wilgus, C.K., Hastings, B.S., Kendall, C.G., Posamentier, H.W., Ross, C.A. and Van
Wagoner, J.C. (eds.): Sea-Level Changes: An Integrated Approach,
125–154. SEPM Special Publication 42, Tulsa.
Posamentier, H.W. & Morris, W.R., 2000. Aspects of the stratal architecture of forced regressive deposits. In: Hunt, D. and Gawthorpe,
R.L. (eds.): Sedimentary Responses to Forced Regressions, 19-46.
Geological Society of London, Special Publication 172, London.
Posamentier, H.W., 2001. Lowstand alluvial bypass systems; incised vs.
unincised. American Association of Petroleum Geologists Bulletin,
85(10), 1771-1793.
Prestholm, E. & Walderhaug, O., 2000. Synsedimentary faulting in a
Mesozoic deltaic sequence, Svalbard, Arctic Norway; fault geometries, faulting mechanisms, and sealing properties. American Association of Petroleum Geologists Bulletin, 84(4), 505-522.
Róžycki, S.Z., 1959. Geology of the north-west part of Torell Land,
Vestspitsbergen. Studia Geologica Polonica, 2, 1-98.
Schumm, S.A., 1993. River response to baselevel change: implications
for sequence stratigraphy. Journal of Geology, 101(2), 279-294.
Steel, R., 1977. Observations on some Cretaceous and Tertiary sandstone bodies in Nordenskiöld Land. Norsk Polarinstitutt Årbok 1976,
43-67.
Steel, R., Gjelberg, J. & Haarr, G., 1978. Helvetiafjellet Formation (Barremian) at Festningen, Spitsbergen a field guide. Norsk Polarinstitutt Årbok 1978, 111-128.
Steel, R. & Worsley, D., 1984. Svalbard’s post-Caledonian strata; an
atlas of sedimentational patterns and paleogeographic evolution:
Petroleum geology of the North European Margin, 190-235. Norwegian
Petroleum Society (NPF).
Steel, R.J., Crabaugh, J., Schellpeper, M., Mellere, D., Plink-Björklund,
P., Deibert, J. & Løseth, T., 2001. Deltas and Rivers on the shelf
edge: Their relative contributions to the growth of shelf margins
and basin-floor fans (Barremian and Eocene, Spitsbergen). In: Weimer, P., Slatt, R.M., Coleman, J., Rosen, N.C., Nelson, H., Bouma,
A.H., Styzen, M.J. and Lawrence, D.T. (eds): Transactions Gulf
Coast SEPM Annual Conference, Houston, 981-1009.
Swift, D.J.P. & Thorne, J.A., 1991. Sedimentation on continental margins, I: a general model for shelf sedimentation. Shelf Sand and
Sandstone Bodies: International Association of Sedimentologists,
Special Publication, 14, 3-31.
Takata, H., Seto, K., Sakai, S., Tanaka, S. & Takayasu, K., 2005. Correlation of Virgulina fragilis Grindell & Collen (benthic foraminiferid) with near-anoxia in Aso-Kai Lagoon, central Japan. Journal of
Micropaleontology, 24, 159-167.
Takata, H., Takayasu, K. & Hasegawa, S., 2006. Foraminifera in an organic-rich, brackish-water lagoon, Lake Saroma, Hokkaido, Japan.
Journal of Foraminiferal Research, 36(1), 44-60.
Talling, P.J., 1998. How and where do incised valleys form if sea level
remains above the shelf edge. Geology, 26(1), 87-90.
Torsvik, T.H., Carlos, D., Mosar, J., Cocks, L.R.M. & Malme, T.N., 2002.
Global reconstructions and North Atlantic paleogeography 440
Ma to Recent. In: Eide, E.A. (coord.): BATLAS - Mid Norway plate
reconstruction atlas with global and Atlantic perspective, 18-39. Geologival Survey of Norway.
Van Wagoner, J.C., Posamentier, H.W., Mitchum, R.M., Vail, P.R., Sarg,
J.F., Loutit, T.S. & Hardenbol, J., 1988. An overview of sequence
stratigraphy and key definitions. In: Wilgus, C.K., Hastings, B.S.,
NORWEGIAN JOURNAL OF GEOLOGY
Posamentier, H.W., Ross, C.A., van Wagoner, J.C. and Kendall, C.G.
(eds.): Sea-Level Changes-An Integrated Approach, 39-45. SEPM
Special Publication 42.
Van Wagoner, J.C., Mitchum, R.M., Campion, K.M. & Rahmanian,
V.D., 1990. Siliciclastic sequence stratigraphy in well logs, cores,
and outcrops; concepts for high-resolution correlation of time and
facies. American Association of Petroleum Geologists Methods in
Exploration Series, 7, 55 pp.
Walker, R.G., 1992. Facies, facies models and modern stratigraphic
concepts. In: Walker, R.G. and James, N.P. (eds.): Facies Models;
response to sea level change, 1-14. Geological Association of Canada,
Ontario.
Wellner, R.W. & Bartek, L.R., 2003. The Effect of Sea Level, Climate,
and Shelf Physiography on the Development of Incised-Valley
Complexes: A Modern Example From the East China Sea. Journal
of Sedimentary Research, 73(6), 926-940.
Woolfe, K.J., Larcombe, P., Naish, T. & Purdon, R.G., 1998. Lowstand
rivers need not incise the shelf; an example from the Great Barrier Reef, Australia, with implications for sequence stratigraphic
models. Geology, 26(1), 75-78.
Ziegler, A.M., Raymond, A.L., Gierlowski, T.C., Horrell, M.A., Rowley,
D.B. & Lottes, A.L., 1987. Coal, climate and terrestrial productivity;
the present and early Cretaceous compared. In: Scott, A.C. (ed.):
Coal and coal-bearing strata: recent advances, 25-49. Geological
Society of London, Special Publication 32.
Århus, N., 1991. Dinoflagellate cyst stratigraphy of some AptianAlbian sections from Northern Greenland, Southeast Spitsbergen
and Barents Sea. Cretaceous Research, 12, 209-225.
Paralic sedimentation on an epicontinental ramp shelf 359