Geology and Palynology of the Triassic Succession of B J@M@Ya

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Geology and palynology of the Triassic succession of B j@m@ya

ATLE MBRK, JORUNN 0s VIGRAN AND PETER A. HOCHULI

MIrk, A., Vigran, J. 0. & Hochuli, P. A. 1990: Geology and palynology of the Triassic succession of BjIrncaya. Polar Research 8, 141-163. The Triassic succession of Bjdrndya (200 m) comprises thc Lower Triassic Urd Formation (65 m) of the Sasscndalen Group, and the Middle and Upper Triassic Skuld Formation (135 m) of the Kapp Toscana Group. These units are separated by a condensed ?Middle Triassic sequencc represented by a phosphatic remaniC conglomerate (0.2 m). The Urd Formation consists of grey to dark grey shales with yellow weathering dolomitic beds and nodules. Palynology indicates the oldest beds to be Diencrian: ammonoid faunas in the middle and uppcr part of the formation arc of Smithian age. The organic content (c. 1%) includes kerogcn of land and marine origin. reflecting a shallow marine depositional environment. The Skuld Formation is dominated by grey shales with rcd weathering siderite nodules. There arc minor coarsening upwards sequences; the highest bed expobed is a 20 m thick, very fine-grained sandstone. Palynomorphs indicate a late Ladinian age for the lowcr part of the formation. and macrofossils and palynomorphs indicate Ladinian to Carnian ages for the upper part. Sedimentary structures, a sparse marine fauna and microplankton indicate deposition in a shallow marine environment. The organic residues contain dominantly terrestrially derived kerogen. Atle M~rkand Jorunn 0s Vigran, Continental Shelf Institute (IKU), N-7034 Trondheim, Norway; Peter A. Hochuli, Esso Rep, 213 Cours Victor Hugo, B.P. 150,33321 Bgles, CEDEX, France; August 1989 (revised February 1990).

Bjorn~ya,the southernmost island of the Sval- Geological setting bard Archipelago, is situated on the Stappen High close to the western margin of the Barents Shelf, The sedimentary succession of Bj~rnoyacom- midway between Spitsbergen and the mainland prises three main geological elements (Horn & of Norway (Fig. 1). Despite its small size Orvin 1928) (Fig. 1): (178 km2), the island has an extensive geological -Triassic, c. 200 m of fine-grained clastics. succession of late Precambrian to early Mesozoic -Upper Devonian to Permian, c. 1,200111 of age that aids significantly the understanding and clastics and carbonates. interpretation of the geology of the adjacent Bar- -Hecla Hoek basement, c. 1.200 m of meta- ents Shelf area. morphosed clastics and carbonates. Geological study of the island began at the end The Hecla Hoek basement forms the moun- of the last century, the Triassic succession was tainous southern part of Bj~rn~ya,and clastics described by Anderson (1900); his fossil col- and carbonates of Devonian to Permian age are lection was described by Bohm (1903). Detailed exposed over most of the remainder of the island. mapping (Horn & Orvin 1928, 1:50.000 geo- The uppermost Permian Miseryfjellet Formation logical map) gave little new information on the (and partly the Hambergfjellet Formation) rests Triassic succession. Comments on the Triassic with angular unconformity on earlier Permian and succession of the island were included in the pre-Permian units. The Triassic rocks are present regional studies of the Svalbard Archipelago by only on the highest mountain of Bj0rn0ya. Mis- Buchan et al. (1965) and Tozer & Parker (1968). eryfjellet, where they rest disconformably on the These studies were, however, hampered by lack Miseryfjellet Formation. This contact is marked of new field data. A new phase of investigation by a topographic break in slope (Fig. 2) that of the Triassic rocks, started by Soviet geologists reflects the great difference in hardness of the (Pchelina 1972; Krasilshchikov & Livshits 1974), Permian limestones and the Triassic shales. was continued by Norwegians (Mork et al. 1982; The Devonian to Permian succession was Bjor0y et al. 1983; Worsley et al. in press). briefly described by Worsley & Edwards (1976) A. Mlrk, J. 0. Vigrun & P. A. Hochuli

Bjarr narya a. Localization b. Geological map c. Geology of Miseryfjellet area d. Stratigraphical column and

0- 1 2 3km

NORWEGIAN

SEA 0 BJBRN0YA

BARENTS SHELF

a d. Geology and palynology of the Triassic succession of’Bj@rn@ya 143

fossil (Lowy 1949). (The three metres long amphibian was rediscovered in 1984 during a geological excursion by the Continental Shelf Insti- tute (IKU). The remains were protected and excavated the following summer by technicians of the Palaeontological Museum in Oslo, and are now under preparation.) In their stratigraphical synthesis of the Triassic succession of Svalbard Buchan et al. (1965) cor- Fig. 2. Miseryfjellet viewed from the north-east. To the left the related the upper fossiliferous part (64m) with vertical cliff comprises Permian carbonate, of the Miseryfjellet the Kapp Toscana Group and the underlying Formation. On the succccding plateau. softer ?riassic shales 126 m with the Sassendalen Group on the basis of form thrcc peaks: from the Icft, Vcrdandc. Urd and Skuld. the observations of Anderson (1900) and Bohm (1903). They regarded the fossiliferous beds as and the sedimentological evolution of the late Ladinian, based on the ammonoids reported by Palaeozoic succession has been presented by Bohm. For the entire Sassendalen Group on Worsley et al. (in press). They show that tectonic Bj@rn@yathey suggested a general Early and stabilization took place in the Permian and that Middle Triassic age, although they indicated that shallow marine platform environments developed the lower part of these shales could have been over the entire island, probably extending onto deposited in the Permian (Buchan et al. 1965, fig. large parts of the Barents Shelf. According to 22). The biostratigraphy was further elaborated Krasilshchikov & Livshits (1974), the entire late by Tozer & Parker (1968), who made comparisons Permian (Kazanian and Tatarian) is missing, with the type sections in Canada (Tozer 1961, although biostratigraphical evidence for this 1967). Tozer & Parker postulated that ‘. . . the hiatus has not been presented. The stable tectonic presence of the Upper Ladinian Sutherlandi Zone situation continued into the Triassic, although a in Svalbard is shown by the occurrence of Dax- large gap in sedimentation spans the Palaeozoic- atina (= Dawsonites) canadensis (Whiteaves) on Mesozoic boundary. Bj@m@ya(Bohm, 1903), in beds assigned to the Kapp Toscana Formation by Buchan et al. (1965, p. 47). Daxatina canadensis is restricted to the Previous research on the Triassic of upper part of the Sutherlandi Zone in British Columbia and the specimens from Bj@rn@ya, BjOrnOya described as having rounded saddles, seem to The presence of Triassic rocks on Bj~rn~yawas have been correctly identified by Bohm. Bohm’s first recognized on the basis of fossils collected assignment of the beds to the Carnian is not during the Nathorst expedition of 1898, and the justified . . .’. Concerning the fauna derived from succession was studied and sampled by Anderson the overlying beds, Tozer & Parker kept open the (1900). Andersson’s fossil collection was docu- possibility that this could be of Carnian age. mented by Bohm (1899, 1903) who proposed a The most thorough and interdisciplinary studies Carnian age for the uppermost 40m of the suc- of the Triassic of Bj@rn@yawere carried out by cession; the age of the lower 140 m was not estab- Soviet expeditions in 1969 and 1970 (Pchelina lished. Anderson (1900) preferred an early 1972). By comparing the stratigraphical suc- Triassic age for these lower beds, though Nathorst cession with that of the other islands in the Sval- (1910) advocated a Carnian age for the entire bard archipelago and with evidence from shale succession on the basis that it did not contain macrofossils (several of them poorly preserved), the very abundant bivalve fauna (daonellids or Pchelina postulated the presence of Lower Posidonia) common on Spitsbergen. (50m), Middle (0.2m) and Upper (140m) Tri- British ecologists observed a labyrinthodont assic sediments separated by depositional breaks amphibian approximately 100 m below the top of in the upper part of the Lower Triassic and in the the peak of Urd, and they covered the finds Middle Triassic. Pchelina (1972) correlated the because they were unable to collect such a large lowermost beds (22m) in Bj@rn@ya,on litho-

~~~~ ~~ Rg. 1. Maps and stratigraphical column of Bjcirnoya. Modified from Horn & Orvin (1928) and Worsley & Edwards (1976). 144 A. MGrk, J. 0. Vigran & P. A. Hochuli logical criteria, with the lower part of the Sas- Formation and included in the Sassendalen sendalen Group, and tentatively indicated an Group. The phosphate conglomerate was named Induan (Griesbachian and Dienerian) age for the Verdande Bed and included in the Urd For- these beds. The characteristic, although poorly mation. The whole upper part of the succession preserved, ammonoid (Euflemingites)of the over- was named the Skuld Formation and correlated lying beds is well known in the Smithian of Spits- with the lower part of the Kapp Toscana Group. bergen. ?Arctoceras blomstrandi was reported by The organic geochemistry of the Triassic rocks Pchelina from a bed two metres below the phos- has been presented by Bjoroy et al. (1983) who phate conglomerate and she assigns this bed to reported a mixture of herbaceous and amorphous the Smithian. It should be recognized, however, organic material in the Urd Formation, and that Pchelina postulated a major break in sedi- mainly woody and herbaceous mixed with mentation in the upper part of the Olenekian amorphous material in the Skuld Formation. The (Spathian). The two main units were interpreted organic content varies between 0.6 and 2% and as separated by a thin remanie conglomerate of the deposits, especially the siltstones, contain a phosphate cemented nodules containing variable fair amount of extractable hydrocarbons. The amounts of other mineral grains. In fact the phos- source of the hydrocarbons in the Urd Formation phatic conglomerate reflects multi-sedimentation is regarded as interbedded shales, while the silt- processes, and Pchelina regarded the nodules as stones of the Skuld Formation contain hydro- representing remains of the entire Middle Trias- carbons both from interbedded shales and sic, as similar phosphate nodules are reported in possibly from shales in the underlying Urd For- this part of the succession elsewhere in Svalbard. mation. The chromatograms of the lowermost The uppermost part of the succession contains beds of the Urd Formation are, however, similar macrofossils dated as Carnian, and Pchelina cor- to those from Palaeozoic samples. The maturity related this with the Upper Triassic, on the basis of the succession corresponds to the lower part of of similarities with the other Svalbard islands, theoil window (i.e. 0.9-l.l%Ro), and shows that mainly Sorkapp Land, pointing to the dominance a few kilometres of overlying rocks have been of detrital (?Permian) clastics in the lower part, eroded. The Triassic succession on Bj~rnoyahas and the change from dolomitic beds and con- a fair to good potential to source hydrocarbons. cretions of the Lower Triassic succession to dominantly siderite concretions in the upper part. A transition in clay mineralogy was also reported, The Triassic sediments and the section contains on average approximately one percent organic carbon; the Lower The Triassic beds are preserved only upon the Triassic succession has a higher v/C ratio and a Permian mountain plateau that constitutes the higher extractability than the upper part. This was basal part of Miseryfjellet (Figs. 1 and 2). Soft attributed to the kerogen being mainly of marine Triassic shales form three peaks: Urd, Skuld and origin in the lower part and mainly derived from Verdande. The most complete succession (type higher plants in the upper part of the section. section for all units, Fig. 3) can be studied along The Soviet expeditions also resulted in a tec- the southern ridge of the highest peak (Urd), tonic study, concentrating mainly on the pre- from the cairn at 346.6 m above sea level to the Triassic development of the island (Krasilsh- top of the mountain at 536m. The basal beds chikov & Livshits 1974). According to these (Fig. 5) are also well exposed at the locality Osten authors, the principal faults in the Permo-Triassic between Urd and Verdande (Figs. 6 and 7). The complex have a northeastern trend inherited from Triassic beds rest disconformably, with a few deg- older fault systems. Based on the work of Pchel- rees northerly dip, on the more resistant lime- ina, they assigned the lower part of the Triassic stones of the Miseryfjellet Formation. Parts of to the Urd ‘Suite’ and the upper part to the Skuld the section are covered by shale debris from the ‘Suite’. overlying slopes. After a reconnaissance study in 1977, formal lithostratigraphical units were defined for the Tri- The Urd Formation assic succession by Merk et al. (1982). who mainly adopted the stratigraphical concepts of Pchelina The Urd Formation (65 m) consists of shales and (1972). The lower 65 m were assigned to the Urd siltstones with some sandstone beds at the base; Geology and palynology of the Triassic succession of Bj@rn@ya 145

dolomite nodules and beds become increasingly common in the upper part of the formation. The upper part of the underlying Miseryfjellet Formation was deposited in open marine environments, as demonstrated by a diverse fauna of brachiopods (both productids and spiriferids), bryozoans and echinoderms preserved in a marly limestone with abundant glauconite. A thin crust at the top of this unit consists of dolomite and ankerite veins that impregnate the fractured surface. It is only a few centimetres thick, and may have formed during either subaerial exposure or a submarine depositional hiatus between the a deposition of the Miseryfjellet and Urd Forma- z tions. Krasilshchikov & Livshits (1074) indicated a that the upper parts of the Permian (Tatarian and E Kazanian) are missing, but there is no reported vu fossil evidence to support this view. Palynological v1 investigations (Konieczny 1987, written cornrn.) D 0 resulted in the recovery of poorly preserved J material with long-ranging spores and pollen, t- 3 which only allow a general Permian dating. At the base of the Urd Formation type section Y n (Figs. 3 and 5) a fine-grained brownish weathering

0 laminated sandstone with wave ripples is overlain by a weakly consolidated and irregularly laminated a bed (0.3 m thick) which contains abundant Y glauconite. Then follow three thin partly laminated beds, the highest of which shows some bioturbation and wave ripples on its top. These lowermost beds contain abundant reworked debris, phosphate and glauconite grains, as well as abundant iron-oxides between the grains. The abraded nature of the grains suggests that they were derived from the underlying Permian unit. At Osten (Figs. 5,6 and 7),1.3 km north of the type section, a more shaley development is seen, although glauconite-rich planar bedded sandstones are also present, resting conformably on a well developed dolomitic crust in the Miseryfjellet Formation. The lower 25 m of the Urd Formation contain no macrofossils and sparse bioturbation is only observed in the lowermost beds, which are partly covered by scree. The main part of the succession consists of grey laminated silty shale, with thin (10-20 cm), yellow weathering, dolomitic siltstone beds. The lowest and thickest (50 cm) bed is planar laminated, and has linguoid wave ripples

Fig. 3. Interpretative sedimentological section of the Triassic succession of Bjornoya, measured along the southern slope of Urd. Legend in Fig. 4. Thick arrows indicate transgressive development, thin arrows regressive development. 146 A. Mlrk, J. 0. Vigran & P. A. Hochuli

Legend Ird, south m

Carbonate nodules

Siderite nodules Planar lamination Dolomite nodules Basal Triassic Beds

[TI Carbonate cement H Hummocky bedding 0 Glauconite Pyrite nodules Phosphorite nodules .+ Ripples A Wave ripples !+!I) Biotur bation A Chondrites @k%&'tpk Amphibian e Fish remains Gastropods v Brachiopods 9 Brachiopods,productids 0 Bivalves 0 Ammonoids @ Ammonoids in scree a Echinoderms M Bryozoans Plant remains Osten Q m Covered

Fig. 4. Legend to sections 1

1.3 km 0

0 V v -1 Frg. 5. Sections of'thc basal Triassic beds: southernmost part of Urd and Osten. Legend in Fig. 4. Geology and paiynology of the Triassic succession of Bjornoya 147

abundant in the Sticky Keep Member in Spits- bergen. The number of siltstone beds increases towards the top of the formation, giving the section the appearance of a minor coarsening upward unit, although the coarsening is not as pronounced as often seen on Spitsbergen. The siltstone beds, dominated by quartz and with only subordinate mica, contain abundant dolomite cement in the lower part of the unit. Towards the top of the Urd Formation, the silt content decreases and the siltstones are replaced by dolomite beds. Faint Fig. 6. The Urd and lower part of the Skuld Formations on the lamination is normally seen in these beds, and southern slopc of Vcrdandc. The Permian limestone and basal bioturbation is sparse and restricted to very few Triassic hcd\ aic cxpoacd at the locality Osten in the right part beds. of the photo. The silty dolomitic beds close to the top of the formation contain a few poorly preserved in its upper part. The overlying siltstone beds are ammonoids and bivalves. These beds have been laminated, one showing linguoid wave ripples. treated in detail by Pchelina (1972), who regarded Ripple drift lamination was observed in one bed them as a condensed sequence, including periods 12 in above the base. The remainder of the suc- of low or non-deposition. Pchelina also reported cession contains parallel laminated beds without the presence of the ammonoid ?Arctoceras blom- traces of bioturbation. The organic material strandi. A fish jaw fragment from this level is reflects mixed marine and terrigenous sources. assigned to Saurichthys (Franz-Josef Lindemann, In the middle and upper part of the Urd For- pers. comm. 1989), a genus mainly known from mation, from approximately 25 m above base, the the 'Fish Horizons' of Smithian age on Spits- sediment shows darker colours than below. In bergen (cf. Stensio 1925). The dolomites are argil- the lower part of this interval poorly preserved laceous, partly laminated and recrystallized. ammonoids occur as imprints in dolomite There are common imprints of bivalves, which cemented nodules and siltstone beds. These are often occur as small cavities filled by drusy car- referred to the genus Euperninigites by Pchelina bonate minerals, mostly dolomite but also quartz. (1Y72) and by Wolfgang Weitschat (pers. comm. The dolomite beds are overlain by a few metres on our material); this genus is very common in of carbonaceous, argillaceous and silty rocks with the lowermost beds of Smithian age elsewhere in dolomite concretions. Pchelina (1972) also Svalbard. Fish remains are also observed in the reported abundant algal filaments and a high con- central part of the sequence; such remains are tent of organic matter in these beds. The Verdande Bed is a thin conglomerate of grey phosphatic nodules (Fig. S), which rests on the upper dolomite bed of the Urd Formation. The dark grey nodules range up to 10 cm in diameter, and include globular and irregular forms; many are flattened. The nodule bed is also access- ible on the southern slope of Verdande, where a more diverse assemblage of nodules can be sampled than at the type locality which has been visited by more geologists during the last decade. The nodules have a heterogeneous composition of embedded clastic grains and phosphate intraclasts, but no body fossils have been found. Thin sections from the phosphate cemented nodules (Fig. 8) display high but variable con- Ftg. 7. The basal sandstone beds of the Urd Formation which overlie the limestones of Miseryfjellet Formation at the locality centrations of clastic grains. Some nodules con- Osten. tain heterogeneous grain assemblages including 148 A. MGrk, J. 0. Vigran & P. A. Hochuli

mica flakes and abraded gfauconite grains, while others are dominated by quartz. The degree of sorting also varies, and in one thin section the quartz grains are better rounded than in the others. The clastic grains indicate a heterogeneous source. Most of the nodules contain grain supported textures and the phosphate occurs as a microcrystalline cement between the clastic grains, although in small areas the clastic grains are floating in the phosphate matrix. Fossil fragments in the nodules include sponge spicules, bivalve fragments, ostracode shells and the algae resembling Mizzia. Sponge spicules and the Mizzia-like algae are most abundant and are generally phosphatized, although small parts of the fossil walls may consist of chert. Ooids occur in two thin sections and are mostly phosphatized; some have central cavities filled with minerals such as glauconite, quartz, pyrite and more sel- dom kaolinite and clay matrix. Cavities in intraclasts are either empty or filled with secondary minerals such as glauconite, kaolinite and pyrite. Three thin sections have been studied by electron microscope and analysed by microprobe. The mineral composition of the amorphous phosphate varies very little between the nodules and between the phosphatic intraclasts and the matrix. Cal- culation of the mineral formula shows that there is scarcely any carbonate present in the apatite structure, while fluorine is abundant. This composition contrasts with results from Middle Tri- assic phosphate nodules from Spitsbergen, which consist of francolite (carbonate apatite).

The Skuid Formation The upper 135 m of the section on Urd mountain are assigned to the Skuld Formation, which consists of several minor coarsening upwards sequences, grading from grey to dark grey shales with red weathering siderite nodules, to fine- grained sandstone (Fig. 3). A grey shale directly

Fig. 8. Nodules (a) and thin section photos (be) from thc Vcrdande Bcd. b. Thin section of phosphatc nodules. Phos- phatized intraclast (I) is cmbeddcd in a grain-supported phosphate ccmcntcd sandstone. Light colourcd grains are quartz. grcy grains are glauconitc (G). c. Phosphate cemented sandstone with phosphate intraclasts (I). ?sponge spiculcs (S) and the alga Mizzia (M). d. Phosphatizcd oolitcs cmhcdded in ii phosphate matrix. Grey colourcd grains arc glauconitc (G). c. SEM backscatter electron photo of an ooid in phosphatic matrix (Ph), note that ooid walls arc also phosphatizcd. The cavity of the ooid contains glauconite (G). kaolinitc (K) and pyrite (P): quartz grains in the matrix arc grcy (0). Geology and palynology of the Triassic succession of Bj@rn@ya 149 Skuld Formation overlies the Verdande Bed, and contains abundant small siderite nodules. The siderite is fine- Lower sandstone cycle grained (micritic), and only contains minor quartz m grains. The nodules vary from only a few centimetres to tens of centimetres in diameter. The latter flattened discs often form nodular beds, which vary in abundance upw'ard throughout the formation. There are no silt or sandstone beds in the lower few metres of this shale, but such beds occur from approximately 10 m above the base of the formation and the abundance of thin siltstone beds increases upwards through the lower sequence, although very fine sand grade is rarely reached. Current activity is indicated by asym- metric ripples in the lower beds, while hummocky cross lamination and wave ripples interbedded with parallel lamination occur in the upper part of the succession. Plant debris are abundant, especially as minute fragments on top surfaces of siltstone beds. Approximately 100m above the base of the section, a sandy interval (Fig. 9) contains abundant thin sandstone beds with planar lamination, hummocky bedding and wave ripples. The beds become coarser, thicker and more abundant upwards, and culminate in two sandy beds a few metres thick, separated by a few metres of shale. Linguoid wave ripples and plant fragments are abundant in these sandstones. The sandstone interval grades upwards into grey shale with silt and sand lenticles. A three metre long labyrinthodont amphibian (Fig. 10) was found between these sandstone beds. The amphibian remains consist of fragmented phosphatic bones preserved in a shaley interval between silt/sandstone beds. Combinations of wave ripples and hummocky bedding indicate shallow depositional environments. Marine fossils occur both below and above the sandy part of this interval. Most probably the amphibian lived at least partly on land, and this part of the sequence may have been deposited close to the shoreline. Several minor coarsening upwards sequences (mainly from shale to siltstone) occur between 120 and 175 m. These sequences vary from only a few metres to nearly 10 m in thickness. Occasional bivalves are present, mostly daonellids or Halobia. Sparse rippling and hummocky bedding are also observed, although the bedding in the

Fig. 9. Sedimentological section from the lower sandy cycle of the Skuld Formation. Note localization of amphibian between rhe thin sandstone beds. Legend in Fig. 4. 150 A. M@rk,J. 0. Vigran & P. A. Hochuli

Fig. 10. The head and some ribs of the amphibian. Thc frag- mcntcd tos\il was plotcctcd by silicon during cxcavation. Pholo Bjern Tore Simonsen. siltstones and sandstones is mostly irregular. The upper sandstone unit contains both wave ripples and hummocky cross bedding. Some beds have sparse bioturbation in their upper part. At 168 m, a bedding surface has abundant gastropods, mostly preserved as siderite steinkerns. The top sandstone (Fig. 11) comprises very fine- to fine-grained thinly to thickly bedded (0.1 to 1 m) sandstone, and is slightly more than 20 m thick. Below this sandstone, some thin siltstone beds show wave ripples. Parts of the sandstone contain low angle cross-beds; some beds continue across the entire exposure in the cliff below the mountain top. Several large and ~omeminor car- Fig. 12. a. Thin section photo in crossed polarized light showing bonate nodules are present. Bioturbation is the heterogeneous nature of sandstones from thc Skuld observed locally. plant debris are abundant, and Formation (189.00 m). b. Combined SEM backscatter and cathodoluminescence image of a sandstone from the Skuld imprints Of bivalves are common’ especially Formation (106.10 m).The smooth grey areas arc quartL grains towards the top. The fauna (Q) and overgrowth (O), the lighter areas are luminescing ammonoids (Bohm 1903). primary quartz grains (L). Lighter grey grains are mica flakes Thin sections (Fig. 12) generally show a het- (M) and the rough grey matrix is composed of clay minerals erogeneous mineralogy, and diagenetic fabrics (‘1. The bright rim cement is siderite.

are more extensive in the upper sandstone unit than in the sandstone in the middle part of the formation. Mica and plagioclase are abundant in the upper sandstone, and plastic squeezing, mainly of clay minerals, has blocked most of the pores, while later quartz overgrowth has sealed off any remaining porosity. Cementing minerals in the sandstone include quartz, illite and chlorite, in decreasing amounts. There is no preserved primary porosity or observed secondary porosity. Fig. 11. The upper sandstone of the Skuld Formation, Urd mountain. The Carnian cycle is interpreted as starting at the This contrasts with the ‘lean level of the arrow. quartz sandstones of the Urd Formation. Geology and palynology of the Triassic succession of BjfirnQya 151

Mineralogy by XRD Thirty-nine samples of shales, silty shales, carbonate and phosphate nodules have been analysed by X-ray diffraction (Fig. 13). Trends throughout the succession reflect both primary mineralogy and diagenesis. Analytical proccdure: The samples were gently crushcd and sucked onto milliporc filters for whole rock analysis. Thc minerals were identified as indicated below, and the quantification was based on peak height multiplied by the width of the peak at half maximum height. The results wcre multiplied by a weighted factor relative to quartz. The 78, minerals were split into kaolinite and chlorite by calculating the relative percentage of the height of the 3.58A and 3.54A peaks, respectivcly. Phosphate was detected by three characteristic peaks (2.808,, 2.688, and 2.62A); the major peak at 2.808, was used for calculations. The d-values and the weighted factor for the different minerals are: Smectitc: approximately 14A, 0.35. Mixed layer minerals: 10-148,, 0.55. Illite: lOA, 1.4. Kaolinitc and Chlorite: 78,, 0.7. Quartz: 4.268,, 1.0. K-feldspar: 3.24& 0.5. Plagioclase: 3.19A, 0.5. Calcite: 3.038,, 0.25. Dolomite: 2.89& 0.2. Siderite: 2.79.&, 0.25. Apatite: 2.80A, 0.3. Pyrite: 2.718,, 0.7. The shales of the Skuld Formation have a higher clay mineral content than the Urd Forma- tion, and there is an abrupt increase at the formation boundary. The increase is due to higher proportions of both illite and 7A minerals. Kao- linite is dominant over chlorite in the Urd For- mation, while the reverse is seen in the Skuld Formation. Smectite is detected in the Skuld For- mation as well as in the uppermost metres of the Urd Formation. The concentrations of quartz and feldspars simply reflect the silt and sand content of the shales. Alkalifeldspars are only found in minor amounts in the Skuld Formation, while plagioclase is common throughout the section, but most abundant in the upper unit. Diagenetic minerals occur as cement in clastic beds and in nodules. Dolomite is only recorded in the Urd Formation. The nodules of the Verdande Bed have phosphate cement without any calcite, while in the remaining part of the Skuld Formation nodules consist of siderite, and calcite is only present as a minor constituent (cement) in some siltstone beds. Dispersed pyrite is common as a minor constituent in the Urd Formation and it is present in the shales of the Skuld Formation as discrete nodules.

Palynology The palynological investigations involved the Fig. 13. Plots of XRD-results. study of about 140 samples from the Urd Forma- W a 0 a are brackets in metres; other sample in Numbers taxa. section of of list base above Alphabetic c. heights 14a. are Fig. in BJ0RN0YA OF entrance of 16). order and Decimal sample numbers 15 their to (Figs. Bjdmoya. refer of illustrated is Numbers Triassic taxa. taxon RANGE CHART,TRlASSlC of the from the list that indicate (*) selected palynomorphs section. b. Numerical asterisks PALYNOLOGICAL of the in chart; levels range appearance the in approximate Stratigraphic are numbers a. 14. Fig. numbers entrance PLANKTON POLLEN, SPORES & VARlA. Alphabetically listed 1. I Acritarchs. undifferentl.aretl 57 Brachysaccus spp c..4lispoporites microreticulahrs Relnhardt 1Y61 Lundbladisuora SD cf L. obsoleta Balrne 1Y70 (251 2 Micrhysfridiurn spp 58 Succinctisparites grandior Alisporires spp (2X) Lundbladtipora spp (29) 1 Micrhystridium setasessitante 59 Triadispora verrucala AnapiculaIisporites spiniger (Leschik)Reinhardt I96 I (YO) Lvco~odtaciditeskokenrr Van der Ecrn 1983 (891 4 Leiosphoeridium spp 60 Deltoidospora spp Annulispro folliculoso (Rogalska) de Jersey 1959 (72) Lycopodiacidites cp 5 Verylrachium 'pp 6 I Duplicisporites spp Arabisporitesfimbriatus (Klaus)Maedler 1964 (73) Neoraislrickia taylorii Playford & Lkttrnann 1964 (62) 6 Tasmanites sppp 62 Ncoraislrickia taylorii Aratfisporites macrocavatus Bjarke & Manum 1977 (74) * Ovalipollispseudoals (Thiergan) Schuurmann I976 (49) 7 Cymatiosphaera sppp 63 Schrzosporis spp Aratrisporites sp. 2 Hochuli & al. 1989 (75) Ovalipollu spp (771 64 Porcellispora longdonensir * Arah'sporites spp (2.0 Perotrililes SD (78) POLLEN. SPORES & VARlA 65 Asseretospora gyratra Araucariacites spp (98) Plaesiodrcty& mosellanum Wdle 1970 (71 ) R Protohaploxypinus sppp 66 Zebrasporites interscriptus Asseretospora gyratra (Playford & Denmannl Schuurm I Y77(65 ) Podocarpidites sp P cf rouse; Pocock 1970 (93 I 9 Densoisporites spp 67 Uvaesporites sp IAulisporitesostigmosus (Leschlk) Klaus I960 (99) Podosporites amicus Scheurmg 1970 (46) 10 Bibaccate pollen. untlifferenriate~i68 Protodiploxypinus gracilis * Bhardnwjispora labichensis Jansonlus 1962 (3I) Porcellisuora Ionadonensis (Clarke) Scheurmg 1970 (64) I I Cordonispora sppp 69 Carnisporites sp. Bisaccare pollen. undifferentiated (10) * Pretico&ipollen&s spp (14) I2 Proprisporites pococki 70 Kraeusrlisporites cooksonae Brach.vsaccus spp (57) * Proprisporitespococki Jansonius 1962 (12) I3 Rewanispora cf. vermiculata 7 I Plaesiodictyon mosellanum Calamosporo spp (94) Protodioloxvoinus eracilis Scheurme 1970 (68) I4 Pretricolpipollenites spp 72 Annulispora folliculosa * Camarozonosporites rudis (Lecchik) Klauc 1960 ("7) Pr0tod~lor;btnus&or BjErke L banuni 1977 15 Taeniaesporites sp U 73 Arahisporites fimbriatus Compenio gigas Schulz 1967 f Protodiuloxvuinus ornatus Sclicurmp I970 ((I)) 16 Densoisporites playfordii 74 Aralrisporites macrocavatus Carnisporites sp. (69) Protodi&x~pinus spp. (32) I7 Densoispariles nejburgii 75 Aratrisparites sp. 2 Chasmatosporites apertus (Rogalska) Pocock & Jansonius 1969 Protohaploxvpinus samoilovichi (lansonius) Hart 1964 (20) I X Lunatisporites pellucidus 76 Dictyophyllidites spp. t Chasmatosporites major (Rogalska) Ndsson 19% ProtohaDloxvDinus SDD. (8) I9 Cycadopites spp. 77 Ovalipollis spp. * Chasmorasparites spp. (83) * Punc&po&s fun&;, Balme 1963 (30) 20 Protohaploxypinus samoilovichi 78 perotililes sp Chordaspontes spp. (87) Punctatosuoriies walkomii de Jersev 1962 (56) 21 Kraeuselisporites apicu~otus 79 Staurosqccites quadrifuls Circurnsniatites sp. (92) * Rrtisu1cit;s spp. (95) 22 Endosporites papillatus 80 Zebmsporites spp Conbaculatisporites hopenensis Bjzrk- & Manum 1977 (94) * Rewanispora vermiculata Antonescu & Taugo Lantz 1973 (I 3) 23 Aralrisporites spp XI Cordaitina sp. cf. C. gunyahnsis Conbaculatisporites sp * Schuaeiosporites rorsleyi Bjarke & Manurn 1977 (40) 24 Lunalisporites rpp 8 2 Lunatisporites prllucidus Concavisporites spp (55) Schuosporis spp (63) 25 Lundbladisuora SP cf L. obsoleta 83 Chosmatosporites spp. Cordadina minor (Pautsch) (35) * Semiretisuoris SD. 1 196) 26 Kraeuselisporites.spp 84 Conbacuhtisporites hopenensis Cordaitina sp cf. C. gunyalensis(Pant & Shrivast)BaltnelY7R(Xl) SrmtretiFporis Fpp. I KSI 25 'Fungal rernam type I ' 85 Semirefisparis spp cf Corollina spp. * Slaplinisporifer ruminus tBalrne) Pococh 1962 2X A:isporites spp 86 Zebrasporites kahleri Cycadopites spp. ( 19) 2r iundbladispora spp h7 Chordaspontrs \pp Deltoidospora \pp (60 * Slakaktes q&dnJ&s Dolby & Balrne 1976 (79) 30 Punctatisporites fungosus XX Eurornrniiditrs \pp - I)ensoispontr, nelburgii ISchulzI Ralrne IYW (17, Sfriatoobicites ayhrgii Visscher (ScheuMg) 1970 (42) 3 I Bhardwajispora labichensis hU Lycopoduxtditrs kokrnii - Uensoisporitrc plavfordit (Bdmer I>etiinm 1063 I 101 Striatqabieites balmei Klaus 1964 (43) 3 2 Protahaploxypinus spp Yll Anopiculatisporiter spmger Densoispnrirrs \pp (9I * Sfriatoabieites SD A Scheurine 1970 (S3) ?,3 Triadispara 'p. YI StaplinuporirPr ,pp Dirtyophr.lliditrr cpp I 761 Sfriatoabieites spp (47) - ? 1 l'itreisporites pallidus 92 Circumsiriatites ip. Duplicisporites spp (61 Succinctisparites grandwr Leschlk 1956 (58) 35 Cordailma minor 93 Podocarpidites sp P cf rouse; * Echinitosporites iliacoides Schulz & Krutzsch 1961 (52) Taeniaesonntes SD. Ll Jansonius 1962 (15) 36 Triadispora plicato 94 Calamospora spp Endospon'tespapillatus (22)Jansoniu' 1962 Thomson'isporitei toralis Lesclilk 1956 ( 100) Ephedripites sppp SDD Enzonalasuorites viaens Leschlk 1956 Triadisuora obscura Scheurine 37 95 Retirulcites 11 I970 (44) 38 Lunatisporites noviaulensis 96 Semiretisparis sp I Enzonaloiporites dinsus (Leschik) Dolby & Balm 1976 Triadi.+ora plirota Klau, I Yfit 76, 39 Gibeosporiles lativerrucosus 97 Camarozonosporites rudis Ephedripites spp. (371 - rrradispura vrrrurata (Schulii Schrunng 1Y70 (5Yi 40 Schizneiosporites worsleyi YX Araucariacites spp Eucommiidites murogranuhtus Scheuring 1970 (48) * Triadispora sp. (33) 41 IUiniles chitonoides 99 Aulisporites astigmosus Eucommiidites spp. (88) Uvaesporites sp (67) 42 Striatwbirites ayhrgii 100 Thomsonisporites toralis * 'Fungal remain type I' Hochull & al (27) Verrucosisporites spp. 43 Shiatuabieites balmei * Gibeosporites lativerrucosus (Leschik) Leschlk I959 (391 Vitreisporitespallidus (Reissmger) Nilsson 19.58 (34) 44 Triadispora obscura Gordoni.rpora fossulata (Balrne) Van der Eern 1983 Voltziacpaesporites heteromorphus Klaus 1964 (5 I ) 45 Leschikisporis aduncus Gardonispara sppp ( 1 I ) Zebrasporites interscriptus Klaus I960 (66) 46 Podosporites amicus * Illiniter chitonoides Klaus I964 (41 * Zebrasporites kahleri Klaus lYb0 (86) 47 Sfriatwbieites SDD. Infernouollcnites CDD (54) Zebrasporites spp.. (RO) 4X Eucommiidites microgranulntus K~aeu.&po~ites ipiculatus Janson~us1962 (21 ) 49 Ovalipollis pseudoalatus Kraeuseli.sporites cooksonae (70)(Klaus) Detunann 1963 PLANKTON 50 Protodiploxypinus ornatus Kraeureli.sporites cuspidus Balrne 1963 Acriiarchs. undifferentiated( I1 5 I Voltziaceaesporites heteromorphus Kroeurelirporites spp (26) Cymatiosphaera spp (7) 52 Echinitosporites iliacoides Kyr1omupori.s 'pp Leiosphaeridium spp (4) 53 Shiatoabieites sp A Lrrchikirporis aduncus (Leschik) Potonie 1958 (45) * Micrh.vstridium setasessilante Jansoniu~I962 (3) 54 Infernopollmites spp. Lunatigorites noviaulensis (Leschk) Scheunng 1970 13x1 Micrhysfridium spp. (2) 55 Concavisporites spp 1~unati~porile.rpellucidus(Gouhm) Helby IY69 (18) Tasmanites sppp (6) 56 Puncmosporites walkomii Lunatispordes \pp (24) Veryhachium spp (5) 154 A. Mlrk, J. 0. Vigran & P. A. Hochuli tion, the Verdande Bed included, and the Skuld considered to be located around 165.0m but is Formation. not clearly defined palynologically. About half of the samples were barren, and are not included in the distribution chart (Fig. 14a). The palynomorph assemblages of’ the Urd Most of the palynomorphs recovered are poorly Formation preserved (Figs. 15 and 16), resulting in dif- ficulties in identification. Some samples yielded The palynomorphs from the lowest part of the reasonably well preserved and diverse micro- Urd Formation (0.05-2.0 m) are poorly floras; variations in the diversity of the microfloras preserved. Indeterminate bisaccate pollen, cavate are attributed largely to differences in the state spores ( Densoisporites nejburgii, Kraeuselispo- of preservation. There are, however, clear dif- rites sp.), acritarchs (Micrhystridium setasessi- ferences between assemblages dominated by tante, Micrhystridium spp., Veryhachium sp.) and spores and acritarchs in the Urd Formation (Fig. leiospheres are dominant. Proprisporires pococki 14a) and the spore or pollen dominated assem- and Rewanispora cf. uermiculata occur at 0.7 m; blages of the Skuld Formation (Figs. 14a and Cycadopites sp. is quite common, in contrast to 15). An alphabetic list of the taxa recorded is the succeeding interval. Pretricolpipollenites sp. presented in Figs. 14b and c. occurs sporadically and Aratrisporites spp. occurs The recent study by Hochuli et al. (1989) regularly together with bisaccates. reviews the relevant palynological studies for the A corresponding assemblage characterized by Barents Sea area, and establishes a palyno- abundant Cycadopites sp., Pretricolpipollenites stratigraphic framework for the Triassic of this and numerous acritarchs and leiospheres com- area. The study was based on material from prises ‘Assemblage 0’ of Hochuli et al. (1989), onshore Svalbard and from scientific and explo- which has been recovered from the Vardebukta ration drilling in the Barents Sea. In the present Formation in Spitsbergen, above the oldest Tri- study the palynomorph assemblages from Bj~rn- assic palynological ‘Assemblage P’ in Festningen. 0ya are compared with assemblages ‘A-P’ of Farther north in the Bertilryggen section this Hochuli et al. assemblage occurs in association with a Dienerian Two palynomorph assemblages are recorded fauna. In the present investigation Proprisporites from the Urd Formation (Fig. 14a): pococki has also been found in an ‘Assemblage 4.05-2.0 m, the Dienerian ‘Assemblage 0’. 0’ association in BjBrnciya. Unpublished results Between 2.0 and 6.0 m, a non-diagnostic Early (Vigran) from cored material from the Barents Triassic assemblage. Sea show that the taxon ranges into the Late -6.0-64.7 m, the Smithian ‘Assemblage N’. Smithian Wasatchites tardus ammonoid zone, and The nodules from the Verdande Bed yielded thus extends higher than recorded by Hochuli et only a few palynomorphs. The record of Densoi- al. (1989). sporites nejburgii in one sample (65.05 m) is taken Similar assemblages, with common Cycudopites as evidence for an age older than Middle Anisian. and including Proprisporites pococki, were However, the possibility of reworking has to be described from the Early Triassic of western Can- considered. ada by Jansonius (1962) and from Greenland In the Skuld Formation we recognize the fol- (Griesbachian) by Balme (1980). Utting (1985, lowing palynological assemblages (Fig. 14a):’ 1989) records P. pococki and Gnetaceaepollenites -65.5-c. 164.0 m. a Late Ladinian assemblage steeuesi in the oldest Triassic ‘Tympanicysta sto- (probably ‘Assemblage G’). schiana - Striatoabieites richteri‘ assemblage zone -Sample 28 at around 169 m and the sample at of Melville Island in the Sverdrup Basin. 167.0m contain a diverse microflora com- Jarosenko & Golubeva (1981) reported two parable to the early to ‘middle’ Carnian ‘aspects’ of a late Early Triassic ‘Complex 11’ from ‘Assemblage F-D’ of Hochuli et al. (1989). the Timan Pechara region, and considered them -170.0.-193.0 m, an undifferentiated Carnian to represent stratigraphically different levels, fac- microflora. ies variations qr: phytogeographic provinciality. The assemblages suggest that much of Anisian One assemblage, which resembles the oldest and Ladinian time may be unrepresented and assemblage (?Dienerian) in Bj~rn~ya,is dom- that a substantial hiatus occurs between the two inated by Densoisporites spp. and Cycadopites formations. The Ladinian-Carnian boundary is spp., and may have abundant acritarchs. Geology and palynology of the Triassic succession of Bj@rn@ya 155

Apart from the occurrence, often in aeoisporites worsleyi and the frequent occurrences abundance, of ‘Fungal remains type 1’ at 6.0 m, of lllinites chitonoides, Oualipollis pseudoalatus the composition of the assemblages remains quite and Leschikisporis aduncus. homogeneous up to the uppermost part of the Urd A relatively rich and diverse assemblage is Formation. They are characterized by abundant recorded from 66.0 m, 1 m above the Verdande spores, including Punctatisporites fungosus. Bed (Figs. 14a and 15). It is characterized by Rewanisporites cf. verrniculata occurs occasion- abundant spores, mainly Leschikisporis aduncus ally. Variations in diversity are regarded as due and Concavisporites spp., as well as bisaccate to the different states of preservation. pollen. The lowest records of Echinitosporites The samples, particularly up to 42.0 m, contain iliacoides, Triadispora verrucata, Podosporites poorly preserved palynomorphs. The better pre- amicus, common Chasmatosporites spp. and served material between 43.0 and 64.0m has a Ovalipollis pseudoalatus are in this association, higher proportion of large spores, indicating an which is comparable with a Late Ladinian increased terrestrial influx. Cavate spores are assemblage in the Barents Sea area (Hochuli et common, especially Densoisporites spp.. D. al. 1989). nejburgii and Kracuselisporites spp., as well as Well preserved palynomorphs have been Aratrisporites spp. Hochuli et al. (1989) term this recordedat80.0and85.5 mwhere thestratigraphic association ‘Assemblage N’ and also report it incoming of species such as Annulispora folli- from the Tvillingodden Formation in Spitsbergen. culosa, Kraeuselisporites cooksonii, Plaesio- The late Early Triassic ‘Complex 11’ of Jarosenko dictyon mosellanum, Stauroasaccites quadrifidus & Golubeva (1981) is dominated by Verru- and Zebrasporites interscriptus is indicative of an cosisporites spp., Punctatisporites spp. and Ara- age no older than Late Ladinian. These species trisporites spp., and is reminiscent of the as- have previously been reported from the Late Tri- semblage in the upper part of Urd Formation, assic of Spitsbergen, Hopen and Kong Karls Land supporting the view of Jarosenko & Golubeva (Bjaerke & Dypvik 1977; Bjaerke & Manum 1977; that the regionally different aspects of their Smith et al. 1975). They are also present ‘Complex 11’ represent different stratigraphical (Vigran unpublished data) at the base of the levels. Tschermakfjellet Formation (Carnian) and in the The samples show very poor productiveness in uppermost part of the Sassendalen Group the uppermost part of the Urd Formation (64.C- (Ladinian) in Spitsbergen. 65.0 m), and have a higher proportion of densely Hochuli et al. (1989) differentiate two assem- aggregated degraded material. The aggregates blages (G and H) in the upper part of the Ladinian have a granular structure which may possibly be of the Barents Sea area on the basis of the extinc- related to the activity of blue green algae. Algal tion of a distinctive acritarch ‘Cyrnatiosphaera structures have also been reported by Pchelina sp. 1’. Echinitosporites iliacoides occurs in both (1972) from this level. assemblages and ranges to the top of the Ladinian, The distinct change in the distribution pattern whereas ‘Cyrnatiosphaera sp. 1’ seems to be of palynomorphs above the level of the Verdande absent from the higher assemblage (G). In the Bed (Fig. 14a) gives clear evidence for the impor- present material Cyrnatiosphaera sp. 1 has not tant break in deposition. The presence of Den- been found. This may be due to the generally soisporites nejburgii is one feature the Verdande poor preservation of the palynomorphs and Bed has in common with the underlying part of deterioration of this rather fragile acritarch, or it the Urd Formation. However, this species ranges could mean that only ‘Assemblage G’ is present up into the Early Anisian, where it occurs rather in the uppermost Ladinian part of the Skuld For- sporadically. It is also possible that it represents mation. On the other hand, the two assemblages reworking from the Lower Triassic sediments. may represent different marine environments, the more shallow conditions having developed in The palynomorph assemblages of the Skuld Bj~m~yaonly. Formation Palynodebris in the interval from 65.5 up to The lowest sample from the Skuld Formation, at 94.0 m includes abundant tracheids and granulate 65.5 m, contains a poor palynomorph assemblage amorphous aggregates of degraded material. comprising mostly long ranging pollen and spores Spores are abundant in relation to pollen grains. and a few acritarchs. A special feature is Schiz- The overlying layers ([email protected] m) are very 156 A. M#rk, J. 0. Vigran & P. A. Hochuli Geology and palynology of the Triassic succession of Bj@m#ya 157 poorly productive, thus Triadispora spp., 193.0 m contain a rather restricted Carnian assem- although common, are mostly identifiable only to blage and several samples from this interval generic level. proved to be barren of palynomorphs. There is The palynological record above 94.0 m (up to no evidence for an age younger than Carnian in 161.0m) is rather sparse. In addition to the this uppermost part of the Skuld Formation. samples reported in the range chart (Fig. 14a), a Acritarchs are rarer in the Skuld Formation number of barren samples has been prepared than in the Urd Formation, and are virtually from this part of the section. A few samples with absent in some samples, mainly between 103.5 reasonably well preserved palynomorphs occur and 124.0 m. Records of the cenobial alga Pfae- between 161.0 and 176.0m. The highest occur- siodictyon rnosellanum from 80.0 m and in sample rence of Echinitosporites iliacoides and the only 30 from near the top of the Skuld Formation record of the genus Retisulcites in sample 27, reflect an influx from a fresh or brackish water between 161.0 and 167.0 m, is evidence for a latest environment. The discontinuous record of this Ladinian age. Otherwise no important change is species might also be a preservational feature due apparent at this level. to the fragile nature of this palynomorph. The assemblages immediately above (167.0, 168.0ni and sample 28 between 168.0 and Climute and plant geography 170.0 m) are considered to represent the lower part of the Carnian (‘Assemblage D-F’ of Hochuli The Triassic floras of land areas close to Bj@rn@ya et al. 1989). Aulisporites astigmosus, a typical and Spitsbergen are so far known only through Carnian form, has been recorded only in sample their pollen and spores. Though poorly preserved, 28. Illinires chitonoides, which is present in all the palynoflora from Bjarnoya therefore warrants productive samples and is believed to have an some palaeogeographic considerations. Recon- extinction level in the Early Carnian, has its structions of Late Permian and Triassic floras in highest occurrence at 168.Clm. Hochuli et al. the Arctic are few. Wang Ziqiang (1985, fig. 2) report it in ‘Assemblage F’ from the base of the shows a Eurasian arid province extending into Tschermakfjellet Formation in Spitsbergen. On northern China, distinct from the Angaran floras the basis of the stratigraphic position of the inter- to the north, but does not consider the Canadian val we would therefore suggest an Early Carnian Arctic or the Svalbard region. Jacobsen & Van age. There is no positive palynological evidence Veen (1984), comparing conditions on the shelf for a closer dating of this interval in which the along northern Norway, discussed the general organic residues are dominated by coarse wood European pattern of a humid Ladinian and a debris and poorly preserved palynomorphs. drier Carnian climate, as clearly expressed by the The productive samples between 170.0 and palynology in Haltenbanken. There is an increahe

~~ Fig. 15. Selected palynomorphs from the Urd and Skuld Formations. Enlargement Figs. a-h. j, I-n approximately x 750 (sc;llc A). Figs. i. k, rr-q approximately X500 (scale B). Sample numbers rcfcr to Fig. 14a. Stage coordinates rcfcr to Leltz Diaplan microscopc at IKU. Trondhcim. The PMO no. refers to the typc collection of Palcontologisk Museum. Oslo. whcrc the slides arc stored a Arurrisporitev spp. Sample ?.1 m PMO 120 791 :24. 7-YX.6 I3 fret~icolpipo~leni~~~Sample 6.0m PMO 120 792:3Y.3-114.1 c Drri.soi,spporitev pluvfordii Sample 49.0 m PMO 120 793: 16.7-Y8.X d Den.soi.sporites nejburgii Sample 49.0 m PMO 120 793 :33.5-99.9 e Proprisporites pococki Sample 1.2 m PMO 120 794: 32.fG113.2 f Kewariis/mru oermiculuia Sample 0.7 m PMO 120 795:41.4-11.X g Bhurdwajisporu Iuhirhensis Sample 56.5 m PMO 120 803: S 6036 h Micrhystridiurn spp. Sample 1.2m PMO 120 794:[email protected] i Puncfutisporites fungosus Sample 18.0 m PMO 120 796:25.5-110.6 j Sruplinisporifes cnminus Sample 94.0m PMO 120 7Y7:21.492.6 k ‘Fungal remain type 1’ Sample 29.0m PMO 120 7%3:21.Y--309.2 1 Schirueokporites worsleyi Sample 67.0 m PMO 120 799:22.9-112.4 m Trradkpora sp. Sample 167.0111 PMO 120 800:22.6113.4 n Echinitosporites iliucoides Sample 85.5 m PMO 120 XU: 13.2-110.3 o Slaurosuccites quudrifidus Sample 94.0 m PMO 120 797:30.&107.8 p C/?u.~mutosporitesmajor Sample 167.0 m PMO 120 800:22.8-113.2 q Chusmutosporites npertus Sample 85.5 m PMO 120 802: 27.495.5 158 A. M@k, J. 0. Vigran & P. A. Hochuli Geology and palynology of the Triassic succession of Bj@m@ya 159 in humidity during the Carnian, which they found nological assemblages are distinguished by the less evident in assemblages from the more tem- abundance and variety of gymnosperm pollen, perate region of Troms. The Triassic paly- such as Alisporites rnicroreticulatus and Vitrei- nomorph assemblages of the Barents Sea region, sporites pallidus that are common in the other including Bj@m@ya,would, on this basis, be regions, but there are important differences. expected to be related to the temperate conditions Pollen, including Triadispora verrucata, Stauro- of a humid Russian province. saccites quadriJidus and Chasmatosporites spp., Early Triassic palynofloras in Bj@rn@yaare eas- present at this level are believed not to appear ily recognized and compared worldwide on the until the Carnian in more southern provinces. basis of their rich content of trilete cavate spores The number of pteridophyte spores, among like Densoisporites spp., Lundbladispora spp. and them Leschikisporis sp., increases dramatically Kraeuselisporites spp. (Fig. 14a). The spores were towards the labyrinthodont bed, probably as a produced by an ecologically specialized group of result of proximity to a contemporaneous shore- pteridophytes, Pleuromeia spp., that dominated line, and shows that there was a rich vegetation coastal areas. They were replaced by lycopsids partly dependent on humid conditions close to that produced cavate monolete spores, Ara- Bj@[email protected] are strikingly few members of trisporites spp., a group that was well established the dry climate indicators (Visscher & Van der earlier, but which became abundant in the Smi- Zwan 1981) of the Circumpolles group which are thian of Bj@rn@yaand Svalbard (Hochuli et al. so characteristic in the Ladinian and Carnian of 1989), as well as in Arctic Canada (Fisher 1979). southern areas (Van der Eem 1983; Blendinger This early establishment contradicts their known 1988). This would support the inference of a appearance in more southern latitudes, and sup- temperate humid climate in the Ladinian. ports the idea that more humid, temperate cli- The palynology of the Carnian deposits in mates developed in the Arctic when drier Bj~rn~ya(Fig. 14a) compared with that of the. conditions unfavourable for the Aratrisporites Late Ladinian suggests that there were no group persisted in the south. dramatic environmental changes. The large Another characteristic feature of most of the number of pteridophyte spores and the near Urd Formation in Bj@rn@yais the abundance of absence of the Circumpoiles group support the fungal hyphae (‘Fungal remains type 1’ of Hochuli continuation of fairly humid conditions in the et al. 1989), reflecting a local humid environment. area. The same feature has also been recorded (Hochuli et al. 1989) in Spitsbergen, and seems a general feature in Smithian deposits of the Barents Sea Ages and correlations area. On the basis of macrofossils and palynology the The Late Ladinian of the Skuld Formation in following ages may be assigned to the Triassic Bjmncdya is dated on the basis of Echinitosporites succession: iliacoides, which is stratigraphically restricted in The lowest three metres of the Urd Formation the Germanic and Alpine regions (Visscher & contain representatives of palyno-assemblage ‘0’ Brugman 1981). The fairly well preserved paly- of Hochuli et al. (1989), which is also found in

Fig. 16. Selected palynomorphs from the Skuld Formation. Enlargement approximately X750 (scale bar). Sample numbers refer to Fig. 14a. All specimens have stage coordinates referring to Lcitz Ortholux 11 microscopc in the Esso Laboratories, Bordeaux. The slides are stored in the Esso Laboratories, Bordeaux. a Zebrasporites kohleri Sample BJ 27: 31.7-102.0 h (‘rrmumzonospurite.s rudi.s Samplc BJ 27 :44.2-112.2 c Semiretisporis sp. Sample BJ 27 :36.7-95.0 d Ouulipollis pseudoulurus Sample 66.0 m :26.4100.2 e Aufi.rpor-ites usripnosui Sample BJ 2X: 2X.2-Y3.2 f Proroadip[oxypinus oniafus Sample BJ 27 : 26.0-105.8 g Rerisulcires sp. Sample BJ 27:29.&Y5.3 h Giheosporites lutiuerrucosus BJ 27 :25.3-100.3 i Striutuuhieim sp. A Sample 66.0m:21.(k110.2 j IIlinites chilonoides Samplc BJ 27 : 42.2-96.7 k Triudisporu uerrucura Samplc 66.0 m :26.2-309.4 I Prutodiplux~pmuvsp. cf. P. urnulus Sample BJ 27:43.0&109.7 160 A. Mprk, J. 0. Vigran & P. A. Hochuli the Vardebukta Formation of Spitsbergen in beds Formation on Spitsbergen. In Spitsbergen the of Dienerian age. An Early Triassic transgression transition from the Bravaisberget Formation - farther southeast in the Hammerfest Basin is also Botneheia Member to the Tschermakfjellet For- assigned to the Dienerian (Jacobsen & Van Veen mation at the base of the Kapp Toscana Group is

1984), and may thus correlate with that trans- now regarded as being around the Ladinian ~ gression in Bj~rnctya. Carnian transition (Korchinskaya 1982; Mark et The middle and upper parts of the Urd For- al. 1989). The continuous presence of lithologies mation contain the ammonoid Eufiemingites sp. that are similar to those of the Tschermakfjellet of early Smithian age, and the presence of Formation through the major part of the Skuld ?Arctoceras blomstrandi close to the top of the Formation indicates that the change from mature formation shows that this whole interval was to immature mineralogy took place earlier in deposited in Smithian times. The presence of Bj~rn~yathan in the other Svalbard islands. palyno-assemblage ‘N’ supports this age. These beds correlate with the lower parts of the Tvil- lingodden Formation and Sticky Keep Member of Spitsbergen. Depositional cycles The Verdande Bed contains no identifiable M0rk et al. (1989) have described transgressive- macrofossils, but sparse palynomorphs suggest an regressive cycles for Triassic sequences in the Early Anisian or older age. Abundant phosphate Arctic, and demonstrated that most are cor- nodules occur in the Bravaisberget Formation relatable from the Sverdrup Basin through Sval- and Botneheia Member and their presence in bard to the Barents Sea. The incomplete the Verdande Bed was the main basis for its succession of Bjmrn0ya follows the same cycle lithostratigraphic correlation with Middle Triassic pattern, but shows important differences. beds of Spitsbergen, and the proposal that all The marked change in sedimentation pattern, or most of the Spathian is missing in Bj~rn~yafrom fault controlled in the Carboniferous-early (Pchelina 1972). Permian to tectonically stable in the late Permian- The lower beds of the Skuld Formation contain Triassic, has been recognized for the Svalbard palynomorphs representative of palyno-assem- Archipelago by Steel & Worsley (1984) and blage ’G’,or possibly ‘H’, of Hochuli et al. (1989), described from Bjorn~yaby Worsley et al. (in both indicating a Late Ladinian age. No Anisian press). The break in sedimentation between the or typical Early Ladinian palynomorphs were Miseryfjellet Formation and the Urd Formation recorded, The Verdande Bed may, therefore, represents a long period of time, and the basal comprise a remanie deposit of sediments of (Griesbachian) transgression recognized in most Middle Triassic (Anisian) or possibly Early other Arctic areas (M~rket al. 1989) does not Triassic (Spathian) age. A major depositional seem to have affected Bj@mciya. break, with erosion during the Anisian and Early Ladinian, is probable. Dienerian cycle. - The basal sandstone unit at Approximately 40 rn below the top of the Skuld Bjornciya, which is only 1 to 2 rn thick, contains Formation the ammonoid Daxatina canadensis abundant clasts from the underlying formation, confirms the presence of latest Ladinian sedi- and may be regarded as the initial deposit of the ments (Biihm 1903; Tozer & Parker 1968). The transgressive Triassic clastic sequence. At Sor- palynomorph assemblages below this level, kapp Land, on southern Spitsbergen, a trans- although poorly preserved, resemble the Late gressive basal conglomerate (the Brevassfjellet Ladinian palyno-assemblage ‘G’, and samples Bed), regarded as Dienerian in age by Bir- from the succeeding 40m contain some com- kenmajer (1977), overlies both Hecla Hoek base- ponents of the early Carnian ( palyno-assemblage ment and Palaeozoic rocks on the Smkapp- ‘F to D’). There are strong lithological similarities Hornsund High (Worsley & Mark 1978; M@rket between the grey shales, with abundant red al. 1982). The Dienerian transgression of weathering siderite nodules, of the Skuld For- BjQrnaya is thus contemporaneous with the last mation and the Tschermakfjellet Formation on part of the early Triassic transgression in the Spitsbergen. The impure sandstones of the Skuld Svalbard Archipelago and in the Hammerfest Formation are also similar to lithologies reported Basin as reported by Jacobsen & Van Veen by MGrk et al. (1982) from the De Geerdalen (1984). The sedimentation initiated in the Geology and palynology of the Triassic succession of Bj~rn~ya161

Dienerian continued during the next trans- of the remanie conglomerate. However, the het- gression, apparently with deposition in the same erogeneous grain composition and the lithoclasts facies . in the nodules indicate that they represent a variety of facies associations. Possible hiatuses, both Srnithian cycle. - Around 20 m above the base of in the Spathian and the lowermost part of the the section the darker sediments contain poorly Middle Triassic, may indicate a complex local preserved ammonoids that are common in beds subsidence history for this part of the Barents referred to the Smithian elsewhere in Svalbard. Shelf. The colour change in the basal part of the Smi- Late Ladinian cycle. - The dating by palynology thian beds is interpreted as a result of reduced of the basal beds of the Skuld Formation as Late sedimentation rates with a relative increase of the Ladinian and the presence of the latest Ladinian organic content due to a major highstand. This ammonoid Daxatina canadensis some 40 m below event can also be recognized at the base of the the top of the Skuld Formation put some con- Tvillingodden Formation and the Sticky Keep straints on the interpretations as compared with Member elsewhere in Svalbard (Mark et al. the cycle development elsewhere in the Arctic. 1982), and may also be traced to the Sverdrup Nearly one hundred metres of sediments may Basin and other Arctic areas (Mark et al. 1989). have been deposited rapidly, possibly as a result The Smithian palyno-assemblage 'N' of Hochuli of sediment influx from the east. The change in et al. (1989) was recorded from the 6.0m level the mineralogy from the Urd Formation to the upwards in the Urd Formation. Skuld Formation is similar to those observed The upper few metres of the Urd Formation between the Sassendalen and the Kapp Toscana include several silty dolomitic beds with a few Groups elsewhere in Svalbard. On Spitsbergen poorly preserved fossils. These beds have been this transition is thought to occur close to treated in detail by Pchelina (1972), who regarded the Ladinian-Carnian boundary (Korchinskaya them as a condensed interval, including probable 1982). periods of non-deposition. Pchelina reported the presence of the ammonoid ?Arctoceras blom- Carnian cycle. - The upper part of the Skuld strandi in these beds; this species is common in Formation forms a sequence grading from dark Smithian beds elsewhere in Svalbard (Kor- shale to thickly bedded sandstones. The con- chinskaya 1982), where the age is confirmed by sistent Carnian evidence from palynology and palynomorphs. If we accept a Middle Triassic age macrofossils supports an interpretation of this for the Verdande Bed (see below), it seems that part of the succession as representing a Carnian large parts of the Spathian are missing on Bj0r- transgressive-regressive cycle. n0ya or represented by a strongly condensed section. Regional thickness variations

Anisian-Ladinian sedimentation and erosion. - The 200m of Triassic rocks are at present the The poor palynological evidence defining the age youngest deposits on Bjarnaya. As deduced from of the phosphate nodules of the Verdande Bed the maturation level of the organic content as older than Middle Anisian suggests, with the (Bjoroy et al. 1983), they were at one time over- lithological correlation with nodule bearing lain by two to three km of younger deposits, which Middle Triassic sediments on Spitsbergen, that may have been of any age from the late Triassic these rocks formed in the Early Anisian. Early to Tertiary. On Spitsbergen the thickness of the Ladinian transgressions are reported in other Arc- Sassendalen Group varies from 120 to 700 m and tic regions (Mark et al. 1989) and this may have the Kapp Toscana Group ranges from 80 to more resulted in the deposition of the phosphate nod- than 475 m (Mork et al. 1982). ules in Bjarn0ya. Alternatively, as the oldest beds Thickness variation in offshore areas is con- of the Skuld Formation are probably of Late siderable, with highs (Loppa High and parts of Ladinian age, the nodules may not have been the Stappen High) having only a thin Mesozoic deposited before that time as a basal remanie sediment cover, while the basinal successions conglomerate for the Skuld Formation. So far, no (e.g. in the Bj~rn0yaBasin) may comprise up to information is available regarding the thickness 10 km of Mesozoic rocks (Faleide et al. 1984). of the sediments removed during the formation In the Hammerfest Basin more than two km of 162 A. Mark, J. 0. Vigran & P. A. Hochuli

Triassic sediments are present (Worsley et al. tectonic block with a different subsidence and 1988). uplift history from Spitsbergen and the adjacent The thickness of the Sassendalen Group on Barents Shelf areas, although the general pattern Bj~rn~yais in the same range as on the Sorkapp- of sedimentation on Bj~rn~yais similar to that Hornsund High. However, while Lower Triassic observed throughout the Arctic. sediments are thin on the Sarkapp-Hornsund High, they cpmprise all of the Urd Formation on Acknowledgements. -The work is part of the IKU Arctic Cico- program, which is economically supported by A/S Norskc Shcll. Bjarn~ya.The lower part of the Middle Triassic BP Petroleum Development (Norway) Ltd.. Elf Aquitainc succession, in contrast, is relatively thick on the Norgc A/S, Esso Norge a.s.. Fina Exploration Norway Utcnl. Sarkapp-Hornsund High but is only represented A,&, Mobil Exploration Norway Inc., Norsk Agip A/S. Norak by the Verdande Bed on Bjarnaya. These oppo- Hydro as., Phillips Petroleum Co. Norway, Saga Pctrolcum a.s. and Statoil. We also acknowledge the permission 111 include site relationships between two positive features, the rebults from a palynological project carried out for Esao the Sarkapp-Hornsund and Stappen Highs, sug- Norgc a.a. We would like to thank Arne W. Forsberg and gest that they have different uplift and subsidence David Worsley for coopcration in the ticld and for numcrous histories. As indicated on S~rkappaya(south of discussions. Fossils have been idcntified by Wolfgang Weitschat Spitsbergen), with at least 220 m exposed of the (amrnonciids). FranL-Joscf Lindcmann [fish remains) and Jack Babcock (dasycladacean algae); their advice is gratcfully Sassendalen Group, they may have been sep- acknowledged. Thc manuscript benefits from commcnts from arated by a basin. David Worsley, Geoffrey Warrington and Stefan Piasecki. The Skuld Formation correlates with the lower Drawings are by Ingrid Brandslet. part of the Kapp Toscana Group elsewhere in Svalbard, where the Tschermakfjellet and Austjakelen Formations are around 60 m thick. However, there is a gradual transition from these References formations to the De Geerdalen Formation and Andcrsson, J. G. 1900: Ubcr die Stratigraphic und Tcktonik the combined thickness of the group exceeds der Barcn Insel. Bull. Geol. Inst. Unio. Uppsuh 4. 243-2x0. 475 m in eastern Svalbard, while on the Sorkapp- Balmc, 8. E. 1980: Palynology of Permian-Triaaaic boundary Hornsund High it is only 50 m thick. beds at Kap Stosch, Ea\t Grcciiland. Medde1el.w om Gr@ri- These thickness variations conflict with the sug- land 200 ((1). 1-37. Birkcnmajer, K. 1977: Triassic sedimentary formations of the gestion by Faleide et al. (1984) that the Stappen Hornsund area. Spitshergen. Studiu Geologiccc f’oloniccr 2 High (with Bj~rnOya)is connected to the S~rkapp- (8))7-74. Hornsund High. The general structural trend to Bjordy, M., M0rk. A. & Vigran. I. 0. 19x3: Organic gco- NNW-SSE oriented lineaments observed in chemical studies of the Devonian to Triassic cucces\ion on Bjdrneya and the implications for the Barcnts Shelf. Pp. 40- Svalbard and Bjarncbya also contradicts that view, 59 in Bjorby, M. el al. (cds.): Aduunws in Ot&mic (h- and may indicate that a sub-basin, or an area chemistry 1981. John Wilcy & Sons Ltd. with greater subsidence, separated these two Bjaerke, T. & Dypvik. H. IY77: Sedirncntological and pally- areas during deposition of the Sassendalen Group. nological studies of Upper Triassic-Lower Jura\\ic \cdinicnts in Sassenfjorden, Spitsbcrgcn. Norsk Polurin.~~itutrArhok 1976, 131-150. Summary Bjaerke, T. L Manum, S B. 1977: Mchozoic palynology of Svalbard-I. The Rhactian of Hopcn, with prcliminiiry report Only a few of the Triassic transgressions noted by on the Rhaetian and Jurassic of Kong Karls Iirnd. No,:sk Market al. (1989) from the Barents Sea, Svalbard Polarinsriturt Skrifter 165, 1-48. 9 pls. Blendinger, E. 1988: Palynostratigraphy of the Latc Ladiniaii and the Sverdrup Basin can be recognized on and Carnian in the Southeastern Doloinitcs. Rroiew of Bj~rncbya,namely those of Dienerian, early Smi- Palaeobotany and Palynology 53, 329-348. thian, ?Anisian and Carnian age. Even in these Buchan, S. H., Challinor, A,, Harland, W. B. & Parker. J. K sequences normal transgressive-regressive cycles 1965: Thc Triassic stratigraphy of Svalbard. Norsk folur- imtirutr Skrifter 135. 95 pp, were not fully developed, as sedimentation seems Bohm, J. 1899: Uber Triasfossilien der Baren-Insel. Zeitschrifr to have been repeatedly interrupted and parts of der geologlchen Gesellschaft, Berlin B.51, 325-326. the succession eroded, following local uplift. BBhm, J. 1903: Uber die obertriadische Fauna der Bareninacl Important hiatuses occur in the Griesbachian, Kungliga Suenska Vetenskaps-Akademiens Haridlingar 37. I- Spathian, ?earliest Anisian and late Anisian-early 76. Falcide. J. I.,Gudlaugsson, S. T. & Jacquart. G. 1984: Evol- Ladinian sequences. The development of these ution of the western Barents Sea. Marine Petrolerrrn Geology truncated cycles and the abundant hiatuses is I, 12>150. consistent with Bj~rn~ya’slocation on a separate Fisher, M. J. 1979: The Triassic palynofloral succession in the Geology und palynotogy of the Triassic succession of Bj@m#ya 163

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