Lower Cretaceous Lithostratigraphy Across a Regional Subaerial Unconformity in Spitsbergen 287

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NORWEGIAN JOURNAL OF GEOLOGY Lower Cretaceous lithostratigraphy across a regional subaerial unconformity in Spitsbergen 287

Lower Cretaceous lithostratigraphy across a regional subaerial unconformity in Spitsbergen: the Rurikfjellet and Helvetiafjellet formations

Ivar Midtkandal, Johan Petter Nystuen, Jenö Nagy & Atle Mørk

Midtkandal, I., Nystuen, J. P., Nagy, J. & Mørk, A.: Lower Cretaceous lithostratigraphy across a regional subaerial unconformity in Spitsbergen: the Rurikfjellet and Helvetiafjellet formations. Norwegian Journal of Geology, Vol. 88, pp. 287-304, Trondheim 2008, ISSN 029-196X

During development of the Lower Cretaceous succession in the Spitsbergen domain of the epicontinental Boreal Basin, a fall in relative sea-level caused a major subaerial unconformity to form. This unconformity forms the lithostratigraphic boundary between the Rurikfjellet Formation below, and the Helvetiafjellet Formation above. The previous Ullaberget Member in the upper part of the Rurikfjellet Formation was originally defined using the Ullaberget section in Nathorst Land as its stratotype. The Ullaberget section is not representative for the upper sandstone-rich member of the Rurikfjellet Formation, but is chosen here as the stratotype for the new Louiseberget Bed of the Festningen Member. The Louiseberget Bed consists of deltaic sandstone, located above the subaerial unconformity capping the Rurikfjellet Formation, and forms a facies body within the Festningen Member, the fluvially-dominated lower member of the Helvetiafjellet Formation. The Kikutodden Member is here defined as a new member substituting for the Ullaberget Member as the upper, sand-rich part of the Rurikfjellet Formation; the Kikutodden section in Sørkapp Land being the stratotype and the Strykejernet section being new hypostratotype for the member. The Festningen Member and the Glitrefjellet Member in the lower and upper parts of the Helvetiafjellet Formation, respectively, are re-established as formal members.

Ivar Midtkandal, Johan Petter Nystuen and Jenö Nagy, University of Oslo, Department of Geosciences, P.O. Box 1047, Blindern, NO-0316 Oslo, Norway; Atle Mørk, SINTEF Petroleum Research NO-7465 Trondheim, Norway, and Department of Geology and Mineral Resources Engineering, NTNU, Norwegian University of Sciences and Technology, NO-7491, Trondheim, Norway; Ivar Midtkandal, Present address: University of Adelaide, Australian School of Petroleum, Adelaide SA 5005, Australia [email protected]

Introduction with Albian beds being the youngest Mesozoic units pre- served below the Paleocene deposits of the Central Terti Svalbard’s Mesozoic succession is characterized by open ary Basin (Nagy 1970; Mørk et al. 1999). marine through marginal-marine to continental facies associations of mudstone, shale and sandstone deposited During the latest Middle Jurassic to Early Cretaceous in a shallow epicontinental basin (e.g. Kelly 1988; Mørk et (Bathonian to Hauterivian/earliest Barremian), marine al. 1999). General overviews of the geological development clay and mud with sand intercalations of prodelta and/or of Svalbard and adjacent parts of the Barents Sea region shoreface origin accumulated in the Svalbard domain of are given by Steel and Worsley (1984), Nøttvedt et al. the Boreal Basin, presently part of the Janusfjellet Sub- (1993) and Worsley (2008). group in the Adventdalen Group (Dypvik et al. 1991a). This subgroup is subdivided into the Agardhfjellet For- Being part of the Boreal Basin along the northern margin mation (latest Bathonian to Volgian) and the Rurikfjel- of Laurasia (Fig. 1), the Spitsbergen domain of the basin let Formation (Berriasian to Early Barremian). Both comprised several depositional environments including formations are subdivided into several members related alluvial plain, paralic settings such as coastal plain, delta, to variations in sandstone content (Dypvik et al. 1991a; strandplain and shoreface to mud-dominated environ- Mørk et al. 1999). The lithostratigraphic subdivision is ments well below fair-weather and storm wave base. made independently of any sequence stratigraphic con- The basin was characterized by very low overall gradient sideration or genetic interpretation of the succession. slopes, thus giving rise to basin infill dynamics sensitive The overlying Helvetiafjellet Formation has been identi- to fluctuations in relative sea-level and changes in clas- fied as generally bipartite by Parker (1967), with a thick tic sediment input. Variation in these two allogenic fac- sandstone succession at its base, the Festningen Member, tors in combination with ongoing autogenic influence followed by a heterolithic upper part, the Glitrefjellet exerted the main control on the lithostratigraphy of the Member. Stratigraphically higher, the Cretaceous succes- Mesozoic sedimentary succession in Svalbard and in the sion is again mudstone dominated but with several sand- western Barents Sea area. By an oblique uplift of Spitsber- stone intervals, and is named the Carolinefjellet Forma- gen (most in the northwest) in Late Cretaceous time, the tion (Parker 1967; Edwards 1976; Nagy 1970; Mørk et al. Spitsbergen sedimentary succession was deeply eroded 1999). 288 I. Midtkandal et al. NORWEGIAN JOURNAL OF GEOLOGY

Palaeo-land Fig. 1 Boreal Basin palaeogeography at 127 Ma, N showing Spitsbergen’s position relative to major land- Boreal Basin (ocean) Novaya Zemlya masses. Map data is modified from Torsvik et al. (2001, 2002).

Sverdrup Basin

Barents shelf domain Spitsbergen 60˚N domain

Greenland Fennoscandia

LAURASIA 1000 km

127 Ma

The scope of the present paper is to revise the lithostrati- these new observations create the need for a revision of graphy of the uppermost part of the Rurikfjellet type sections and redefinition of members both above Formation and the overlying Helvetiafjellet Formation and below the unconformity. (Mørk et al. 1999). The Ullaberget Member has been defined as a sandstone unit in the uppermost part of the In other parts of Spitsbergen, sandstone units supposed Rurikfjellet Formation, located below a regional erosional to be lateral correlatives to the Ullaberget Member in the unconformity separating the open-marine Rurikfjellet stratotype section are all located below the regional ero- Formation from the fluvial and paralic Hevetia fjellet sional unconformity, at least within the Svalbard domain Formation above the unconformity (Różycki 1959; of the Boreal Basin. For this reason, we propose the name Birkenmajer 1975; Dypvik et al. 1991a, b; Mørk et al. Kikutodden Member of the Rurikfjellet Formation for this 1999). The Ullaberget cliff section has been assigned as sand-dominated unit below the unconformity, while for the stratotype for the member, although this particular the unit above the unconformity, we propose the name sandstone unit is not present at this locality. The first Louiseberget Bed of the Festningen Member (lower part of sandstone unit one encounters when walking up the Ulla- the Helvetiafjellet Formation in Nathorst Land, Appendi- berget section through the shale-dominated Rurik fjellet ces 1 and 2). We also propose to re-establish the formal Formation is the deltaic sandstone here defined as the status of the “Festningen sandstone member” (Mørk et Louiseberget Bed overlying the regional unconformity. al. 1999), as the Festningen Member in the lower part of the Helvetiafjellet Formation, and retain the Glitrefjellet The absence of a thick sandstone unit below the regional Member (Parker 1967) as a formal unit in the upper part unconformity at Ullaberget has been the source of of the Helvetiafjellet Formation. The Glitrefjellet Member repeated misunderstandings regarding the stratigraphy was abandoned as a lithostratigraphic unit by Mørk et al. at this locality during subsequent field activities (e. g. (1999). The changes in lithostratigraphic nomenclature excursions). The deltaic sandstones of the Louiseberget proposed in this paper were reviewed and accepted by Bed have been mistaken for the true Ullaberget Member, the Norwegian Stratigraphic Committee (NSK) prior to as they constitute the lowest sandstone interval at Ulla- submission of the article to the Norwegian Journal of berget. Recent investigations on the northern side of Van Geology for publication. Keulenfjorden in Nathorst Land (Ahokas 2004; Midt- kandal et al. 2005; Midtkandal et al. 2006; Midtkandal 2007; Midtkandal & Nystuen 2009) have shown that the Use of the name Ullaberget Member and regional erosional unconformity here can be traced at related terms through time the base of the lowest sandstone and along the entire cliff face that spans Annaberget, Louiseberget and Ullaberget. The starting point for events leading to use of the term These observations are in accordance with the geological Ullaberget in stratigraphic nomenclature dates back to map covering the area produced by the Norwegian Polar observations made by J. G. Anderson in 1898, dealing Research Institute (Dallmann et al.1990). with the shale-mudstone succession exposed below the sandstone cliffs at Ullaberget, located on the northern As the Ullaberget section on the north side of Van Keulen- side of Van Keulenfjorden. Referring to Anderson, these fjorden was chosen as stratotype for the Ullaberget Mem- observations came to be published by Nathorst (1910), ber of the Rurikfjellet Formation (cf. Mørk et al. 1999), including Anderson’s sketchy drawing of the eastern part NORWEGIAN JOURNAL OF GEOLOGY Lower Cretaceous lithostratigraphy across a regional subaerial unconformity in Spitsbergen 289 of Ullaberget (Fig. 2) and a short note stating that the kammen, see Fig. 3) by Birkenmajer (1975), and in the upper part of the succession below the sandstone cliffs, Agardhbukta area close to the east coast where Dypvik et currently referred to the Janusfjellet Subgroup, consists al. (1991b) reported only silty shales. of shattered dark shale (“dunkle, zerfallende Schiefer” Nathorst 1910) with globular calcareous concretions. The Ullaberget unit was subsequently redescribed by The presence of sandstones at this level is not mentioned Birkenmajer (1975), in a paper dealing with the Jurassic in the report. However, an extensive sandstone body and Cretaceous formations in southwestern Torell Land with thin coal seams and an abrupt lithological bound- (Fig. 3). His concept of this unit follows essentially that ary towards the underlying thick shale were noted. This of Różycki (1959), but he gave it a formal member status is important because the occurrence of sandstone beds at and an emended definition. According to his description, several stratigraphical levels and as upward-coarsening the member is a succession of brownish to black, often parasequences is a significant feature of the Ullaberget bioturbated shales, interbedded with siltstones and sand- unit of later authors (e.g. Różycki 1959; Birkenmajer 1975; stones. Its basal contact is gradational, while its upper Edwards 1976; Mørk et al. 1999; Dypvik et al. 1991a). contact, against the Festningen Member (of the Helve- tiafjellet Formation), is sharp and seems to represent a The first formal use of “Ullaberget” in stratigraphic nam- break in deposition. ing was by Różycki (1959) in his pioneering study of the geology of the region south of Van Keulenfjorden (east- The stratigraphic name Ullaberget Member (sensu ern Wedel Jarlsberg Land and western Torell Land). Różycki, 1959, emended Birkenmajer 1975) as a designa- In this region, he observed at several localities a sandy, tion for the uppermost subunit of the Rurikfjellet Forma- regressive development in the uppermost part of the tion, was applied both in the western and eastern outcrop Janusfjellet Subgroup, and designated it the Ullaberget belts of the Rurikfjellet Formation in subsequent papers, Series. In this connection he referred to the observations e.g. Nemec et al (1988), eastern Spitsbergen; Dypvik et reported by Nathorst (1910), but his short description of al. (1991a), central Spitsbergen; Dallmann et al. (1993), the Ullaberget series is based on the Skiferkammen (pre- Sørkapp Land. viously named Jurakammen) section located in Torell Land. In Mørk et al. (1999), the current authoritative work which revises the lithostratigraphy of the Mesozoic suc- According to Różycki (1959), the upper part of the Rurik- cession in Svalbard, the Ullaberget Member is referred fjellet Formation (his Ullaberget Series) on Skiferkam- to as the uppermost, generally upward coarsening part men contains only three thin sandstone interbeds “with of the Rurikfjellet Formation. It is recognized in all sec- fine-grained quartz gravel” The thickness of these beds tions where this formation is exposed on Spitsbergen. is, however, only 10, 120 and 20 cms, respectively. This The Ullaberget section in Nathorst Land (Fig. 3) was very low sand content makes the Skiferkammen section chosen as its stratotype. The unit was in this work cor- clearly inapplicable as a stratotype or hypostratotype for related with the Kikutodden sediment package, defined the relatively thick, sand-dominated Kikutodden Mem- by Pčelina (1983). The Kikutodden section in Sørkapp ber. The low sand content of this stratigraphic interval at Land, recorded by Edwards (1976), was designated as the Skiferkammen is also apparent from the section repro- hypostratotype for the unit. duced here (cf. Fig. 10). A similar sand-poor development of the upper Rurikfjellet Formation is also shown Pčelina (1983) described the Kikutodden package as sand on the nearby Polakkfjellet (~18,5 km south of Skifer- rich, with thin mud- and siltstone layers. Carbonized

Fig. 2 The Ullaberget outcrop, published in Nat- horst (1910). The sketch, made by Anderson in 1898, shows folded strata (lower left) in the mudstone-dominated Rurik- fjellet succession and a lithologically sharp upper boundary to the Helve- tiafjellet Formation. The figure shows the basis for lithostratigraphic subdivision across the regional unconformity that marks the base of the sandstone beds. (No scale is included in the original). 290 I. Midtkandal et al. NORWEGIAN JOURNAL OF GEOLOGY

Fig. 3 Locality map showing parts of Svalbard, with Nathorst Land inserted. Locali- ties in text are marked with black circles. Long- yearbyen, the largest settlement in Svalbard, is marked with a star.

Konusen Nordenskiöld Myklegardfjellet Land Agardhbukta Glitrefjellet Torellbreen Osbornfjellet Wedel Kvalvågen Jarlsberg Land Polakkfjellet

Keilhaufjellet, Kikutodden

plant remains and coal seams were also recorded within the regional unconformity at the base of the Helvetiafjellet this unit. This description does not indicate an open Formation, (3) The possible presence of a unit in the Ulla- marine shelf environment, which is the setting suggested berget section, corresponding to the original definition of by Mørk et al. (1999) for the Ullaberget Member. Fur- the Ullaberget Member as a sand-dominated member in thermore, the Kikutodden package is listed as a subunit the upper part of the Rurikfjellet Formation (see below), of the Helvetiafjellet Formation in Pčelina (1983). This has to be taken into consideration when naming the new assignment may have been a mistake in the 1983 publi- sandstone member above the unconformity. cation, as Pčelina as co-author of the Mørk et al. (1999) publication regarded the unit as part of the Rurikfjellet Formation and the Ullaberget Member. The Ullaberget – Louiseberget – Anna- berget outcrop area Based on this review the following can be concluded: (1) The first use of the name “Ullaberget” as a lithostrati- Ullaberget is the easternmost of three marked mountain graphic unit (Różycki, 1959, the Skiferkammen section) peaks in Nathorst Land on the northern side of the outer did not involve a sandstone-dominated interval above the part of Van Keulenfjorden. Louiseberget is located fur- regional unconformity and immediately below the Fest- ther to the west and Annaberget is the westernmost of ningen Member of the Helvetiafjellet Formation, or in a these three mountains (Fig. 3). The southern sides of the position lateral to the typical fluvial Festningen Member mountains form a large outcrop area exposing the upper (see below), (2) Based on published data and on the pres- part of the Rurikfjellet Formation, the Helvetiafjellet ent studies we can not definitely exclude the possibility that Formation and the lower part of the Carolinefjellet For- the Ullaberget Member, as currently defined, is present mation. Figure 4 shows the Ullaberget locality with the also in the Ullaberget section, but if so it must lie beneath revised lithostratigraphic subdivision. NORWEGIAN JOURNAL OF GEOLOGY Lower Cretaceous lithostratigraphy across a regional subaerial unconformity in Spitsbergen 291

A discontinuously exposed unconformity at the base of The erosional unconformity on top of the Rurikfjellet the cliff-forming, sandstone-dominated Helvetiafjellet Formation is exposed in the lower slopes of the Ulla- Formation forms the upper boundary of the Rurikfjellet berget, Louiseberget and Annaberget mountains. This Formation that crops out in the lower part of the moun- unconformity separates the dark grey mudstone of the tain slopes. The degree of sandstone content within the underlying shale-dominated Rurikfjellet Formation from uppermost part of the Rurikfjellet Formation is not easy a cliff-forming sandstone unit above. The lithological to estimate, as scree covers most of it and also parts of boundary is very distinct and is marked by a thin, dis- the overlying Helvetiafjellet Formation in this area. The continuous conglomerate bed, with well-rounded extra- Rurikfjellet Formation is, in most exposures, dominated basinal quartzite clasts ranging from 3 to 12 cm in diam- by dark grey to black mudstone and shale with scattered eter. The conglomerate varies in lithology from single siderite concretions, but thin beds of light grey siltstone isolated clasts to a matrix- and clast-supported aggregate and very fine-grained sandstone are present at several of clasts up to 25 cm in thickness. In the Annaberget sec- stratigraphic levels. The Rurikfjellet Formation may also tion, irregularly shaped rip-up mudstone clasts from the here be organized in distal, upward-coarsening units, Rurikfjellet Formation are intermingled with the quartz- but this possible stratigraphic feature has not been con- ite clasts. firmed.

The Rurikfjellet and Helvetiafjellet formations are, in this The regional subaerial unconformity area, affected by tectonic movements associated with the development of the Tertiary fold and thrust belt along the The basal erosional boundary of the Helvetiafjellet For- western coast of Spitsbergen (e.g. Braathen et al. 1999). mation described above in the Ullaberget – Louiseber- The strata are generally tilted towards the east. The thick get – Annaberget section is recorded as having a similar (>200 m) mudstone succession of the Rurikfjellet For- appearance throughout the outcrop area on Svalbard mation is folded disharmonically by shorter wavelength (Steel 1977; Nemec et al. 1988; Nøttvedt et al. 1993; folds relative to the overlying Helvetiafjellet Formation. Ahokas et al. 2005; Midtkandal et al. 2006; Hurum et al. A low-angle thrust fault has cut up-section through the 2006; Midtkandal 2007). The unconformity formed dur- Rurikfjellet Formation and into the overlying Helve- ing the emergence and subsequent drowning of the low tiafjellet Formation in the area between the Ullaberget gradient, shallow epicontinental Boreal Basin (Fig. 1). and Louiseberget mountains and displaced the hanging An unknown amount of the Rurikfjellet Formation was wall towards the east (Fig. 3). The horizontal shortening eroded in the process. along the thrust fault is estimated to be less than 1 kilo- metre. The exposures of the unconformity mark the boundary between underlying mud-dominated, open marine shelf

Fig. 4 The Ullaberget outcrop with the revised Carolinefjellet Formation lithostratigraphic subdivision of the Helvetia- fjellet Formation. Below the regional erosional unconformity, the upper part of the Rurikfjellet Formation is cropping out, and shows dark Glitrefjellet Member Helvetiafjellet shale and thin siltstone Formation beds. The Kikutodden Member is not present. The boundary between the deltaic Louiseberget Bed and the overlying facies of the undiffe- rentiated Festningen 20 m Member is stippled. The Festningen lowest sandstone-rich Louiseberget Bed Member part of the Glitrefjel- let Member consists of tidal bars and tidal channel deposits. Rurikfjellet Regional unconformity Formation 292 I. Midtkandal et al. NORWEGIAN JOURNAL OF GEOLOGY

Fig. 5 The lower boundary of the Helvetiafjellet Formation at Myklegardfjellet, near Agardhbukta, east Spitsbergen (see Fig. 3 for location). This type of contact between the Rurikfjellet Formation and the Helvetiafjellet Formation is typical for several localities across Spitsbergen, where the coarse grained sandstone beds of the Festningen Member rest directly on dark mudstones belonging to the Rurikfjellet Formation. Note the absence of any significant sandstone content in the exposed Rurikfjellet Formation.

and/or sandy shoreface successions in the Rurikfjellet Formation and coarse-grained sandstone and conglomerate above (Figs. 5 and 6).

The sheet-like fluvial sandstone unit is thought to represent mainly deposits laid down by braided streams at the onset of deposition of the Helvetiafjellet Formation, and referred to as the Festningen Member (Edwards 1979; Nemec 1992; Midtkandal et al. 2005). The erosional unconformity is generally overlain by a thin fluvial conglomerate bed, as in the Nathorst Land outcrops described above and also in Kvalvågen (Fig. 6). The diameter of the clasts is up to 15 cm, with a mean of about 5-6 cm. The clasts are well rounded, subspherical and poorly sorted, consisting of hydrothermal quartz, quartzite and chert. The widespread and smooth character of the erosional boundary and the sheet-like geometry of the fluvial sandstone (Figs. 5 and 7) Fig. 6 Erosional unconformity within one of the displaced blocks of may be attributed to frequent events of channel avulsions the Festningen Member at Kvalvågen, SE Spitsbergen. The uncon- on the alluvial to coastal plain, like the process described formity marks the boundary between underlying hummocky cross by Holbrook (1996), due to limited vertical accommoda- stratified sandstone beds of the Rurikfjellet Formation and the coarse grained fluvial conglomerate of the Festningen Member, Hel- tion space during the initial rise in relative sea-level after vetiafjellet Formation. the sea-level fall. NORWEGIAN JOURNAL OF GEOLOGY Lower Cretaceous lithostratigraphy across a regional subaerial unconformity in Spitsbergen 293

Fig. 7 Selected outcrop sections from across Spitsbergen, showing the stratigraphic development of the upper Rurikfjellet and the Helvetiafjellet formations. For locations, refer to Fig. 3. Red line marks the base of the Festningen Member. a): outcrop near Osbornfjellet, (Fig. 3 for location) east Spitsbergen, showing the full development of the stratigraphy in the area; the dark shale beds of the Rurikfjellet Formation are eroded at the contact with the Festningen Member (red line), followed by the heterolithic Glitrefjellet Member (above the solid white line), overlain by the Carolinefjellet Formation (stippled white line); The Festningen Member is ca 20 m thick here. b): Kikutodden Member at Keilhaufjellet, Sørkapp Land, Spitsbergen (Fig. 3 for location). The lowest, dark cliffs are sand-rich beds of the Rurikfjellet Formation, followed by the Hel- vetiafjellet Formation above the red line. Photo: W.K. Dallmann. c): Louiseberget cliff section, with the Helvetiafjellet Formation above the erosional unconformity (red line). d): The upper Rurikfjellet Formation and the Helvetiafjellet Formation at Glitrefjellet, central Spitsbergen. e): Konusen, central Spitsbergen. f): Festningen, at the Mouth of Isfjorden, west Spitsbergen; this is the type locality for the Festningen Member; the strata are tilted to ~90°, with stratigraphic up to the left in the photo (east); photo by Asle Strøm. 294 I. Midtkandal et al. NORWEGIAN JOURNAL OF GEOLOGY

The Kikutodden Member of the Rurikfjellet Kikutodden, Sørkapp Land Formation: a shoreface parasequence set As previously mentioned, the Ullaberget Member of the Rurikfjellet Formation was defined by Birkenma- jer (1975) based on previous work by Różycki (1959). The Ullaberget section was chosen as its stratotype, the unit name being derived from the Ullaberget loca- 200 tion. The logged section of Edwards (1976) at Kikutod-

Glitrefjellet Member den in Sørkapp Land was defined as its hypostratotype (cf. Mørk et al. 1999) (Fig. 8). As documented above, the section in Ullaberget does not possess the composition needed to be the stratotype for the sand-rich member in upper part of the Rurikfjellet Formation. Furthermore, as n = 12 also stated above, in lack of any recognizable major sand- Helvetiafjellet Formation Helvetiafjellet rich unit in the upper part of the Rurikfjellet Formation in the Ullaberget section, the term “Ullaberget member”

Festningen Member has, by visitors to the Ullaberget locality, commonly been n = 30 applied to the unit described and defined in this paper 150 as the Louiseberget Bed in the lower part of the Helve- tiafjellet Formation (see below). This is irrespective of the fact that it is included in the Festningen Sandstone Member on the Norwegian Polar Research Institute map sheet Van Keulenfjorden (Dallmann et al. 1990). Due to all these confusions, the name “Ullaberget” has to be dis- carded as a Member name in the upper part of the Rurik- Kikutodden, Sørkapp Land fjellet Formation, according to the rules for stratigraphic

n = 23 definition and naming (Nystuen 1989, p. 14). LITHOLOGY SEDIMENTARY STRUCTURES 100 n = 47 The Kikutodden succession, reproduced as stratigraphic sectionCongl. M-79 in Mørk et al. (1999, p. 194), is here pro- Cross bedding 200 posed as the new stratotype for the upper, sand-rich

Glitrefjellet Member Sandst. member of the RurikfjelletRipple Formation. lamination Though Pčelina n = 9 Flaser bedding (1983)Mudst./ termed her “KikutoddenWavy bedding package” as part of the Helvetiafjellet Formation, it has become clear that this n = 12 Siltst. Lenticular bedding

Helvetiafjellet Formation Helvetiafjellet unit was meant to be identical with the sandstone-rich successioncoal in the upper part of the Rurikfjellet Forma- Festningen Member n = 26 tion, later referred to as the “Ullaberget Member” (Mørk n = 30 Rurikfjellet Formation Kikutodden Member 150 et al. 1999), seePalaeocurrent above. The name Kikutodden Member 50 is, from the argumentsIntense bioturbation presented above, here chosen as a substitute for the old “Ullaberget Member”. The new n = 29 hypostratotypevertical is the sectionburrows at Strykejernet (Figs. 3 and 9) in Torell Land.Diplocraterion bed

n = 23 Dinosaur footprint LITHOLOGY SEDIMENTARY STRUCTURES 100 n = 47 Congl. Plant fragments Cross bedding Sandst. PlantRipple roots lamination n = 9 Flaser bedding Mudst./C CoalWavy bedding Siltst. Lenticular bedding coal Sideritic nodules

0 mudst. siltst. n = 26 m Rurikfjellet Formation sst.Kikutodden Member cgl. Palaeocurrent 50 Intense bioturbation n = 29 vertical burrows Diplocraterion bed Fig 8 Sedimentological log from Kikutodden, Sørkapp Land (see Fig. Dinosaur footprint 3 for location), modified from Edwards (1976). This succession is Plant fragments proposed as the stratotype for the Kikutodden Member of the Rurik- Plant roots fjellet Formation. The legend is also applicable to logs from Stryke- C Coal jernet, Skiferkammen, Ullaberget and Glitrefjellet (Figs. 9, 10, 12 Sideritic nodules

0 mudst. siltst. and 15), respectively. m sst. cgl. NORWEGIAN JOURNAL OF GEOLOGY Lower Cretaceous lithostratigraphy across a regional subaerial unconformity in Spitsbergen 295

Strykejernet, Torell Land Skiferkammen, Torell Land

80 200

Glitrefjellet Member 70

Glitrefjellet MemberGlitrefjellet C Helvetiafjellet Formation Helvetiafjellet C 40 150 Festningen Member Festningen 30 Helvetiafjellet Formation Helvetiafjellet

10 Festningen Member Festningen

100

100 90

Rurikfjellet Formation 50 50 Rurikfjellet Formation Kikutodden Member 40

Polakkfjellet Bed Polakkfjellet 10

m 0 M Si vf f m c vc Tirolarpasset Member (?) 0 m si vf f m c vc gr cgl Sandstone sand

Fig. 9 Sedimentological log from Strykejernet, Torell Land, modified Fig. 10 Sedimentological log from Skiferkammen, eastern Torell Land. The from Mørk (1978). This succession is proposed as hypostratotype for Rurikfjellet Formation is heavily dominated by shales and mudstones while the Kikutodden Member of the Rurikfjellet Formation. See Fig. 8 for siltstones are strongly subordinate and sandstones are quantitatively insig- legend. nificant. Thus, the Kikutodden Member is absent. See Fig. 8 for legend. 296 I. Midtkandal et al. NORWEGIAN JOURNAL OF GEOLOGY

Helvetiafjellet Formation

Carolinefjellet Formation

Glitrefjellet Member

Festningen Member

Rurikfjellet Formation

Fig. 11 The outcrop at Skiferkammen (referred to as Fotografryggen in Mørk et al. (1999), p. 198, Fig. 3-79), eastern Torell Land. The lithostratigraphic subdivision is well illustrated here, as shown by the annotations. The Festningen Member is estimated to be ca. 25 m thick here.

The Kikutodden Member (Appendix 1) consists of dark (Figs. 8 and 9). In the stratotype, as well as in the hypost- grey to black shale, mudstone, siltstone and sandstone ratotype, the Kikutodden Member is limited upwards lithologies in laminae and beds organized commonly in at by a thick unit of marine shale of the Rurikfjellet For- least three upward-coarsening successions. In central Spits- mation that is in turn truncated by the regional uncon- bergen (from Bohemanflya to Lardyfjellet, the number of formity beneath the Helvetiafjellet Formation, with the such upward-coarsening successions varies from one to fluvial Festningen Member resting directly on the ero- five (Dypvik et al. 1991a, b). Siderite concretions are com- sional surface. At several other localities (Figs. 5, 7, 11), mon in the dark grey and black shale facies. These upward- the Kikutodden Member is not present in the upper- coarsening units are all bounded at their base and top by most part of the Rurikfjellet Formation, or is overlain conformable flooding surfaces in laminated and massive by a thick shale and mudstone unit lacking sand-rich, mudstones; the units are thus parasequences in sequence upward-coarsening bedsets and parasequences. stratigraphic terminology (Van Wagoner et al. 1988).

The parasequences are thought to represent prodelta to The Louiseberget Bed: a bay-head delta shallow marine shelf deposits (Mørk et al. 1999). They sandstone succession may be associated with one large delta complex, or most likely, with several deltaic depocentres, thus representing The Helvetiafjellet Formation is well exposed along the distal equivalents of various delta lobes and/or shore- cliffs in the Ullaberget-Louiseberget-Annaberget outcrop face deposits. These upward coarsening successions area on the northern side of Van Keulenfjorden. The were formed by upward-shallowing on a gently slop- formation is recognizable as a prominent cliff-forming ing ramp. On this ramp the water depth changed from sandstone succession that overlies the mudstone-shale below storm wave base with laminated and bioturbated dominated upper part of the Rurikfjellet Formation in dark grey to black shales, to above fair-weather wave base this area. The Helvetiafjellet Formation at Ullaberget with cross-stratified shoreface sandstone beds forming displays, as everywhere else in Spitsbergen, a lower part the upper part of individual parasequences. The gen- dominated by thick sandstone bodies, the Festningen eral stratigraphic trend within the Kikutodden Member Member, and an upper heterolithic part of alternating is an aggradational or upward-shallowing development marginal marine to coastal plain sandstone and mud- displayed by a set of stacked regressive parasequences stone intercalations (Fig. 12), the Glitrefjellet Member. NORWEGIAN JOURNAL OF GEOLOGY Lower Cretaceous lithostratigraphy across a regional subaerial unconformity in Spitsbergen 297

In most areas of Spitsbergen the Festningen Member is “interpreted as mainly fluvial, although intercalated with Ullaberget, Nathorst Land fluvial-dominated mouth bar and interdistributary bay environments” (Mørk et al. 1999, p. 200). In the mid- 110 dle and eastern part of the Louiseberget section and in the Ullaberget section, the lower part of the Festningen Member forms a sandstone succession resting on the erosional unconformity that cuts the top of the Rurikfjellet Formation. The unit is here defined as the Louiseberget Carolinefjellet Formation 100 Bed of the Festningen Member in the Helvetiafjellet For- mation (Appendix 2). The overlying coal-rich mudstone followed by thin-bedded sandstone beds with thin coal seams are included in the Festningen Member, but not 90 in the Louiseberget Bed (Figs. 12, 13). Gjelberg & Steel (1995, Fig. 3, p. 574) also noted this interval above the basal unconformity of the Helvetiafjellet Formation in the Ullaberget section. 80 An equivalent deposit to the Louiseberget Bed in the type area occurs at Svedenborgstupet, Northern Nathorst Land (Fig. 3). This unit probably represents the same depositional environment, but is separated from the lower Louiseberget and Ullaberget strata by an interfluve 70 area in central Nathorst Land between two sub-parallel incised valleys (Midtkandal 2007). Glitrefjellet MemberGlitrefjellet The thickness of the Louiseberget Bed varies from 2 to c. 25 m, but is typically 12-15 m. The maximum thick- 60 ness is recorded in the central Ullaberget section, where it is estimated to exceed 20 m. The Louiseberget Bed has been traced in the middle and eastern Louiseberget section and along the entire Ullaberget section over a dis- tance of roughly 3 km, semi-parallel to palaeocurrent Formation Helvetiafjellet 50 directions trending towards SSE. The eastern termination of the Louiseberget Bed is not exposed, but its thickness reduction towards the east may suggest a down-dip C pinchout within 1-1.5 km from its easternmost exposure. The thrust fault with a suggested horizontal shortening 40 of less than 1 km between the Ullaberget and Louise- berget mountains (see above) adds to the total depositional dip extent of the Louiseberget Bed; here proposed to have been between 5 and 6 km. The extent along the depositional strike of the Louiseberget Bed is poorly con- 30 strained; its width has been measured to be about 2 km from the Louiseberget locality to its lateral palaeotopo- Festningen Member Festningen graphic bounding escarpment. The western termination Bed of the Louiseberget Bed is rather abrupt, with a significant thickness decrease and ultimate termination over Louiseberget 20 a few tens of metres in the central Louiseberget section. Further west, along the western part of Louiseberget and into Annaberget, the basal sandstones are recorded

Fig. 12 Sedimentological log from Ullaberget, Nathorst Land. The lowest sandstone unit in the Helvetiafjellet Formation is interpre- Rurikfjellet Formation ted to represent a bay-head delta formed in an incised valley during the earliest stages of relative sea-level rise (Midtkandal & Nystuen). 0m This succession forms the stratotype for the Louiseberget Member, m si sand p Helvetiafjellet Formation. See Fig. 8 for legend. 298 I. Midtkandal et al. NORWEGIAN JOURNAL OF GEOLOGY

5,4 km 1 1‘ Annaberget covered Louiseberget covered, faulted Ullaberget W position of log E Carolinefjellet Formation trace in Fig. 12

Glitrefjellet Member fjellet a tion a m r elveti o (continues) Festningen Member H F

Louiseberget Bed 100 m

Rurikfjellet Formation regional unconformity

Fig. 13 Outline profile showing the Annaberget, Louiseberget and Ullaberget outcrop sections in southern Nathorst Land. See Fig. 3 for location. as braided fluvial stream deposits with thin heterolithic get section. The orientation of the cliff section is slightly floodplain deposits near their top, and correspond litho- oblique to the mean palaeocurrent direction, and the true logically to the main fluvial lithofacies of the Festningen clinoform dimensions are thus inferred to be somewhat Member elsewhere on Spitsbergen (Fig. 13). larger than those measured.

The Louiseberget Bed is characterized by a lower sand- The upper part of the Louiseberget Bed is characterized stone with tabular and trough cross-stratified beds. by upward thinning of sandstone beds and ends abruptly Mean palaeocurrent direction is roughly 135˚, with where a 3-7 m thick mudstone unit with thin coal and ±45˚ variation. Grain size of the sand is fine to medium sandstone beds overlies the sandstone interval. A fluvial with scattered 1-1.5 cm conglomerate pebbles and mud- sandstone body forming the upper part of the Festningen stone clasts in the lower 1-2 m. A 10 cm thick bed with Member then overlies this mudstone unit. A subaerial horizontal mudstone lamination and 2-3 cm deep roots unconformity is inferred to be present beneath the mud- marks the top of the first 1-2 m. Single and double mud stone with coal beds (Midtkandal & Nystuen 2009). The drapes are observed within cross-stratified sandstone Louiseberget Bed sandstones are readily recognizable as beds above the lower 1-2 m interval. These sandstone pale yellow in contrast to the white beds of the undiffer- beds are organized in sets of clinoforms, 3-6 m thick (Fig. entiated Festningen Member sandstones. Higher up in 14), separated by discontinuous mudstone horizons. The the Helvetiafjellet Formation, in the Glitrefjellet Member, mudstone beds and laminae thicken downdip along the the sandstone beds are dirty gray and yellow. The lowest clinoforms, forming together a thin discontinuous mud- 1-2 m of the Louiseberget Bed is interpreted to repre- stone bed on top of the regional unconformity and the sent a fluvial deposit that was formed during the earli- conglomerate at the base of the unit. Skolithos burrows est stages of deposition of the Helvetiafjellet Formation. are associated with the mudstone horizons between the The remainder of the Louiseberget Bed is interpreted sets of cross-stratification. Clinoform lengths increase as having been deposited in a shallow, tidally influ- from 3-5 m at the western lateral limit to more than 30 enced bayhead delta comprising sand-rich delta front m where the Louiseberget Bed is thickest in the Ullaber- beds (Midtkandal 2007). Coarse-grained sediment was

Fig. 14 Sandstone succession in the Louiseber- get Member at Ullaberget. Note the clinoform geometries that reflect delta progradation from left to right in the picture. NORWEGIAN JOURNAL OF GEOLOGY Lower Cretaceous lithostratigraphy across a regional subaerial unconformity in Spitsbergen 299 transported by rivers directly into the sea, thus deposit- the upper part of the Helvetiafjellet Formation are distrib- ing sand and pebbly sand in rather steeply dipping large utary fluvial channel sandstone bodies within the paralic foreset units, as progradational clinoforms. The bay-head succession of the heterolithic Glitrefjellet Member (Midt- delta developed as the relative sea-level rose and filled kandal et al. 2007). These relatively thin fluvial sandstone the area where the initial fluvial sediment veneer had bodies may be genetically related to the braidplain depos- been deposited. The presence of single and double mud its of the Festningen Member in updip section, north- drapes suggests that tidal currents regularly reworked the west of the present Spitsbergen outcrops. However, in deltaic foreset beds. The shoreline embayment was the the Spitsbergen domain of the Boreal Basin, these fluvial result of the marine intrusion into a wide incised valley sandstone units are lithostratigraphically integrated archi- that terminated to the west against a knick-point escarp- tectural elements of the Glitrefjellet Member (Midtkandal ment (Midtkandal 2007). The dark mudstone with thin 2007; Midtkandal & Nystuen 2007). coal beds that formed above the interval here named the Louiseberget Bed is interpreted as a coastal plain succes- The Festningen Member is thus a mappable lithostrati- sion that in turn was capped by braidplain sand belong- graphic unit that can be identified as a fluvially dominated ing to the upper part of the Festningen Member. sandstone succession (with notable exceptions) showing distinct lower and upper boundaries in all outcrops A subaerial unconformity separates the deltaic Louiseber- of the Helvetiafjellet Formation in Spitsbergen (Figs. 7, get Bed from the alluvial-coastal plain with coal beds and 11). This sandstone package thus exhibits the characteris- fluvial channel sandstone belonging to the upper part of tics required of a formal lithostratigraphic unit (Nystuen the Festningen Member. The lateral extent of this uncon- 1989, p. 23). Hence, the member is here re-established as formity is unknown, as is also the duration of the diastem a formal unit in accordance with the original definition by or hiatus between the delta and the overlying continental Parker (1967). deposits. Age constraints on the Helvetiafjellet Formation are based on dating of the strata below and above the formation, as no age diagnostic fossils are recorded from the The Glitrefjellet Member continental to paralic succession in between (Grøsfjeld 1992; Gjelberg & Steel 1995; Mørk & Smelror 2001). The Parker (1967) defined this upper member of the Helvetia former Ullaberget Member was inferred as having been fjellet Formation as overlying the Festningen Member, deposited in the Valanginian-Early Barremian, contem- consisting of a heterolithic association of mudstone poraneously with the Rurikfjellet Formation. The Lou- and sandstone of various facies belonging to marginal- iseberget Bed is likely of Barremian age, as has also been marine to non-marine depositional environments. This suggested for the Festningen Member (Mørk et al. 1999). package of heterogeneous strata forms an apparent layer- cake stratigraphy in Spitsbergen (Parker 1967; Nagy et al. 1988). Nemec et al. (1988) suggested that the internal The Festningen Member organization of the Glitrefjellet Member reflects events of delta progradation followed by delta retreat. Gjelberg & The Festningen Member, originally defined by Parker Steel (1995) interpreted the whole Helvetiafjellet Forma- (1967) as a mappable lithostratigraphic unit at the base of tion, including the Festningen Member, to have formed the Helvetiafjellet Formation, was given informal unit sta- by shoreline retrogradation during an overall transgres- tus, as the “Festningen (sandstone) member” by Mørk et al. sion, following an event of sea-level fall and formation of (1999). The reason for the degradation to informal status the basal erosional surface. was “that a clear definition and delimitation against other parts of the Helvetiafjellet Formation is impossible” (Mørk In the depositional model of Gjelberg & Steel (1995), flu- et al. 1999, p. 199), and furthermore, “As shown by Steel vial sandstone incursions in the middle and upper part (1977) and Gjelberg & Steel (1995), the Festningen sand- of the Helvetiafjellet Formation were interpreted as rep- stone member consists of several interfingering sandstone resenting “sandstone lobes” of the Festningen Member. lobes” (Mørk et al. 1999, p. 200). Observations from a As stated above, such an interrelationship between fluvial variety of outcrop areas are in agreement with the original sandstone bodies in the Glitrefjellet Member and the flu- statement by Parker (1967) that the lower sandstone mem- vial sandstone bodies of the Festningen Member may exist ber in the Helvetiafjellet Formation has a sheet-like geom- beyond the outcrop area of Spitsbergen, in a more proxi- etry within the Spitsbergen domain of the Boreal Basin. mal position to the northwest. Mørk et al. (1999), adopt- ing the model view of Gjelberg & Steel (1995, p. 211), The Festningen Member is generally interpreted as being proposed to discontinue the use of the name Glitrefjellet dominated by fluvial, primarily braided stream facies Member because “The base of this unit cannot be defined sandstone beds. The fluvial facies may interfinger locally properly due to the multiple sandstone lobes developed in with floodplain, crevasse splay, fluvial mouth bar and bay- many exposure areas of the Festningen sandstone member”. head delta deposits (Steel 1977; Gjelberg & Steel 1995), as also demonstrated by the Nathorst Land outcrops As also stated in Parker (1967) the Glitrefjellet Member is described above. The “interfingering sandstone lobes” in in most outcrop areas characterized by a lower boundary of 300 I. Midtkandal et al. NORWEGIAN JOURNAL OF GEOLOGY

marginal marine or distal coastal plain mudstone above the fluvial Festningen Member, thus indicating an initial trans- Glitrefjellet gression above the alluvial plain (Fig. 15). This is a rather well marked lithologic boundary that can be mapped throughout the outcrop area in Svalbard. It should be Carolinefjellet Formation stated, however, that in some outcrops the lower boundary 50 is not easily recognized as one single and distinct marine transgressive surface, but appears more like a transitional lithological change from continental to marine facies.

The upper boundary of the Glitrefjellet Member is lithologically more diffuse than the lower boundary, being defined by the lower boundary of the overlying open-marine Caro- linefjellet Formation: “The lower boundary of the Caro- linefjellet Formation is defined at the base of the first coarsening-upward unit or shale-sandstone pair which ends up 40 with the typical, greenish-weathering sandstones of the Dalkjegla Member” (Mørk et al. 1999, p. 204).

The Glitrefjellet Member contains several thin sandstone beds associated with coastal plain mudstone and/ or restricted marine mudstone (Nemec 1992; Gjelberg & Steel 1995; Midtkandal 2002; Ahokas 2004; Midtkandal 2007; Midtkandal et al. 2007). Without high-resolution (microfossil-based) biofacies analysis, in order to distin- guish between coastal plain mudstone and inner shelf to 30 open marine mudstone, it is difficult in many outcrops to find the boundary between the paralic Glitrefjellet Mem- Glitrefjellet MemberGlitrefjellet ber and the open marine Carolinefjellet Formation (Midt- kandal et al. 2007). However, this is a problem related to the definition of the Caroline Formation, and not to the definition of the Glitrefjellet Member and the Helvetiafjel- let Formation (cf. Nystuen 1989, § 2.4.7, p. 13).

Helvetiafjellet Formation Helvetiafjellet The apparent layer-cake stratigraphy of the Glitrefjellet Member likely reflects an aggradational depositional style 20 of interfingering paralic facies belts along an undulat- ing coastline within the Spitsbergen domain during the overall sea level rise (Midtkandal et al. 2007, Midtkan- dal & Nystuen 2009). On a basin-wide scale (beyond the outcrop area on Svalbard), the architectural style is likely retrogradational, with onlaps onto the regional erosional unconformity at the base of the Helvetiafjellet Formation (cf. Gjelberg & Steel 1995).

10 Discussion Recent stratigraphic and sedimentological studies of the Helvetiafjellet Formation and its relation to under- and overlying lithostratigraphic units have revealed the need for a revision of the formal lithostratigraphy, including Festningen Member Festningen

Fig. 15 Sedimentological log from Glitrefjellet, central Spitsbergen. This is the type locality for the upper, heterolithic portion of the 0 VF F M C VC CLAY SILT SAND PEBBL. Helvetiafjellet Formation. The fine grained intervals are partially scree-covered, and inferred to contain fine-grained material. See Fig. Rurikfjellet Formation 8 for legend. NORWEGIAN JOURNAL OF GEOLOGY Lower Cretaceous lithostratigraphy across a regional subaerial unconformity in Spitsbergen 301 the upper part of the Rurikfjellet Formation as well as The stratigraphic record of the Helvetiafjellet Forma- the Helvetiafjellet Formation itself. The presence of a tion in Spitsbergen confirms the view of Parker (1967) subaerial erosional unconformity at the base of the Hel- that this formation can be subdivided in two main mem- vetiafjellet Formation in the Svalbard outcrops calls for bers, a fluvial sandstone-dominated member in the lower a distinction to be made between lithostratigraphic units part and a marginal marine to paralic heterolithic mem- belonging to the depositional system of the Rurikfjellet ber in the middle and upper parts, corresponding to the Formation and those of the overlying Helvetiafjellet For- Festningen and Glitrefjellet members, respectively. The mation. The Rurikfjellet depositional system is that of Louiseberget Bed is a local unit, formed by flooding of a marine shelf, regressive in its middle and upper parts, a relatively deep and narrow depression representing an whereas the Helvetiafjellet depositional system represents incised valley. Correlative bay-head deltas may occur in environments ranging from fluvial to paralic, formed in similar settings in proximal reaches of other incised val- response to fall and subsequent rise in relative sea level. leys at the base of the Helvetiafjellet Formation. Outcrops of this formation are frequently used for educational pur- Concerning the Rurikfjellet and Helvetiafjellet forma- poses on Svalbard. The different facies and origin of the tions several depositional models have been suggested. Louiseberget Bed compared to the remaining fluvially- Regarding the establishment of formal lithostratigraphic dominated part of the Festningen Member are of interest schemes, a genetic understanding of actual depositional when considering the depositional history of the succes- systems is desirable; however, genetic depositional and sion. A lithostratigraphic framework which distinguishes sequence stratigraphic models should not govern the way between these sandstone units is thus considered to be of the lithostratigraphic framework is defined (Hedberg practical value. 1976; Nystuen 1989). In the present revision we wish to turn the attention more to recorded lithostratigraphic features than to genetic models of deposition. Conclusion

The term Ullaberget Member, as originally introduced by The present study has demonstrated the need to revise Różycki (1959), was re-defined by Birkenmajer (1975) and the current lithostratigraphy of the upper part of the formally described by Mørk et al. (1999) as a sandstone- Rurikfjellet and the Helvetiafjellet formations. This revi- dominated member in the upper part of the Rurikfjellet sion can be summarized as follows: Formation. This concept has turned out to be confusing, • The term Ullaberget Member (Różycki 1959; firstly because the original Ullaberget unit of upward- Birkenmajer 1975; Dypvik et al. 1991a; Mørk et al. coarsening regressive shale to sandstone parasequences 1999) should be abandoned as a lithostratigraphic has not been documented in the Ullaberget section, sec- name. ondly, the deltaic sandstone recognized in the Ullaberget • The Ullaberget Member should be substituted by the section belongs to the Helvetiafjellet depositional system, Kikutodden Member as the uppermost sand-domi- developed above the regional erosional unconformity that nated segment of the Rurikfjellet Formation, with separates the Rurikfjellet and Helvetiafjellet formations. its stratotype on Kikutodden in Sørkapp Land and Both of these units, the sandy member in the upper part of hypostratotype on Strykejernet, Torell Land. the Rurikfjellet Formation and the new lower lithostrati- • The Ullaberget section in Nathorst Land is here graphic unit of the Helvetiafjellet Formation need to be defined as the stratotype for the new Louiseberget Bed re-defined and new names applied. The upper member of of the Festningen Member, interpreted to represent a the Rurikfjellet Formation also has a new stratotype. These bayhead delta formed by initial transgression inundat- units are the Kikutodden Member and the Louiseberget ing a local depression in the regional erosional surface Bed of the Festningen Member, respectively, as discussed at the base of the Helvetiafjellet Formation. above and described in the Appendices. • The Festningen Member (Parker 1967) should be re- established as a formal lithostratigraphic unit instead The name Kikutodden Member should be used only for of the informal status given to it by Mørk et al. (1999). the upper, sand-dominated and upward-coarsening para- • The Glitrefjellet Member (Parker 1967) should be re- sequence set(s) of the Rurikfjellet Formation, not for the constituted as a formal member in the upper part of the uppermost part of the Rurikfjellet Formation in those areas Helvetiafjellet Formation, thus cancelling the proposed where it is characterised by thick shale and mudstone suc- abandonment of this name by Mørk et al. (1999). cessions up to the contact beneath the Helvetiafjellet For- mation. The absence of the sand-rich upward-coarsening member in the upper part of the Rurikfjellet Formation Acknowledgements: The authors wish to thank the following: Juha Aho- may be due to the lack of sand deposition, or post-depo- kas for support during field work on Spitsbergen, Winfried Dallmann, sitional regional erosion. Hence, the lithostratigraphic ter- Tore Høy and Kjell-Sigve Lervik representing the Norwegian Commit- tee on Stratigraphy, for valuable comments on an earlier version of this minology should strictly reflect lithostratigraphic proper- manuscript, and John Gjelberg, William Helland-Hansen and Morten ties of the succession, not any presumptions concerning Smelror, referees as appointed by the Norwegian Journal of Geology, for chronostratigraphic or sequence stratigraphic correlations insightful and thorough reviews. Statoil ASA is thanked for providing of the various facies types. part of the funding that made the field work possible. 302 I. Midtkandal et al. NORWEGIAN JOURNAL OF GEOLOGY

Appendix 1: Appendix 2: Formal definition of the Kikutodden Member Formal definition of the Louiseberget Bed

Occurrence: Sørkapp Land, inner Hornsund Occurrence: At Louiseberget and Ullaberget, area, Festningen, central and eastern with an equivalent at Svedenborg- Spitsbergen. stupet, Nathorst Land, Spitsbergen. Status of unit: Formal Status of unit: Formal First use of name: Pčelina (1983) First use of name: Present paper Current definition: Present paper, based on works by Current definition: Present paper Edwards (1976), Dypvik et al. (1991a, Synonym and None 1991b) and Mørk et al. (1999) reference: Synonym and None Origin of name: Louiseberget; a mountain in reference: Nathorst Land, Spitsbergen Origin of name: Kikutodden, a headland near the Type section: Stratotype: Ullaberget, Nathorst Land southernmost point of Sørkapp (Figs. 3 and 12 in present paper) Land, Spitsbergen Depositional age: Barremian Type section: Kikutodden, SE Spitsbergen. Fig. 3 in present paper Dating methods Indirect, stratigraphic relationship and reference(s) with the Helvetiafjellet Formation Hypostratotype: Strykejernet, Torell Land for age: (Parker 1967) (Fig. 9 in present paper) Overlying and Festningen Member of the Depositional age: Valanginian – early Barremian lateral unit: Helvetiafjellet Formation Dating methods Stratigraphic relation to Rurikfjellet Underlying unit: Rurikfjellet Formation and reference(s) Formation. for age: Superior unit: Festningen Member Overlying unit: Shale or mudstone of the Other use of name: None Rurikfjellet Formation or the Thickness: 2-20 m Helvetiafjellet Formation Main lithologies: Sandstone, conglomerate Underlying units: Wimanfjellet Member, Tirolerpasset member (cf. Mørk et al. 1999, p. 194) Lower boundary Marked by the first occurrence definition: of conglomeratic sandstone above Superior unit: Rurikfjellet Formation the >200 m thick shale-dominated Other use of name:None succession of the Rurikfjellet Formation, separated from the Thickness: 10-160 m, 158 m in the stratotype Rurikfjellet Formation by a regional Main lithologies: Shale, siltstone, sandstone erosional unconformity. Lower boundary The lower boundary is defined by Description: The Louiseberget Bed consists definition: the first appearance of sandstones of a thin veneer of fluvial above grey shales of the Wimanfjellet conglomerate at the base, succeeded Member (Mørk et al. 1999, p. 194). by a sandstone up to 20 m thick Description: The Kikutodden Member is recog- with clinoform geometries. The nized in sections of the Rurikfjellet sandstone beds are mainly trough Formation on Spitsbergen and con- cross-stratified, and contain 5-15 cm stitutes the upper, overall coarsen- thick single and double mud drapes. ing-upward sandstone-dominated Within the succession Skolithos part of the Rurikfjellet Formation. burrows are common. The member The member consists of shale, silt- is estimated to be roughly 5 km long stone and sandstone beds forming in the depositional dip direction; individual coarsening-upward suc- its lateral extent is not constrained. cessions as single parasequences, The Louiseberget Bed delta collectively composing the overall sandstone beds can be distinguished coarsening-upward member as a from the upper part of the fluvial parasequence set. In the stratotype, Festningen Member sandstone beds shale is laminated and bioturbated, by their distinct pale yellow colour siltstone and sandstone are paral- compared to the white Festningen lel-bedded, current-ripple laminated Member sandstone beds in Nathorst and cross-stratified. Land. Mudstone and coal seams overlying the bay-head sandstone are referred to the continental part of the Festningen Member. NORWEGIAN JOURNAL OF GEOLOGY Lower Cretaceous lithostratigraphy across a regional subaerial unconformity in Spitsbergen 303

The Louiseberget Bed is interpreted Hurum, J.H., Milàn, J., Hammer, Ø., Midtkandal, I., Amundsen, H. to have formed as a bay-head & Sæther, B., 2006. Tracking polar dinosaurs - new finds from the delta affected by tidal currents. It Lower Cretaceous of Svalbard. Norwegian Journal of Geology 86, 397-402. represents the earliest regressive Kelly, R.A. 1988. Jurassic through Cretaceous stratigraphy of the infill of an incised valley that Barents Shelf. In Harland, W.B. and Dowdeswell, E.K. (eds.): formed during a prior fall in relative Geological Evolution of the Barents Shelf Region, 109-130. Graham sea-level. and Trotman, London. Midtkandal, I., Ahokas, J. & Nystuen, J.P. 2005. The lower Cretaceous Helvetiafjellet Formation, Spitsbergen: paralic environment at References a ramp shelf from falling to rising sea level: Vinterkonferansen. Geological Society of Norway (NGF), Abstracts and Proceedings, Ahokas, J.M. 2004. 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