Spathian-Anisian (Triassic) palynology at the Svalis Dome, southwestern Barents Sea

Review ~f Palaeobotany and Palynology, 70 (1991): 199-216 Elsevier Science Publishers B.V., Amsterdam

199

Spathian-Anisian (Triassic) palynology at the Svalis Dome, southwestern Barents Sea Gunn Mangerud a and Arnfinn Romuld b "Continental Shelf and Petroleum Technology Research Institute (IKU), N-7034 Trondheim, Norway bStatoil a.s. Postboks 300, Forus N-4001 Stavanger, Norway (Received January 9, 1991: revised and accepted May 16, 1991 )

ABSTRACT Mangerud, G. and R~muld, A., 1991. Spathian Anisian (Triassic) palynology at the Svalis Dome, southwestern Barents Sea. Rev. Palaeobot. Palynol., 70:199 216. Based on palynological and faunal evidence, two shallow cores from the Svalis Dome in the Barents Sea are interpreted to represent Upper Spathian to Middle Anisian deposits. The two palynological assemblages recognized, are correlated to assemblages M and L recorded in the Spathian-Anisian deposits of the Sassendalen Group in Svalbard. The palynofacies is characterized by high amorphous content up to the middle part of the Middle Anisian, where there is an increased input of wood, charcoal and more terrestrially dominated remains. This change in palynofacies can be related to a change from marine, dysoxic or anoxic conditions to a more oxygenated environment. A moderately humid climate is interpreted from a slight dominance of hygrophytic palynological elements.

Introduction The I K U Barents Sea M a p p i n g P r o g r a m was initiated in 1984, with the objectives o f collecting and interpreting geological, geophysical and organic geochemical data to reveal the geological history o f the Barents Shelf and also support the exploration for oil and gas in the area. The core sites are situated south-east o f Bjornoya, in the Barents Sea (Fig.l, Table I). The locality, n a m e d the Svalis D o m e (Gabrielsen et al., l990) (earlier k n o w n as the "Dia-structure"), is a dome structure in Bjornoyrenna and was first reported by S u n d v o r (1974) and described by Kristoffersen and Elverhai (1978). At this location dipping strata are b r o u g h t up close to sea floor (Fig.2) with Paleozoic sediments centrally and Mesozoic sediments surrounding (Fig.3). Nine shallow cores were drilled in the Triassic succession in 1986. This paper deals with studies o f the microfloras in the Svalis D o m e cores 7323/07-U04 and 7323/07-U-01 (Table I) which contain well preserved microfloras and give a representative 0034-6667/91/$03.50

d o c u m e n t a t i o n o f the S p a t h i a n - A n i s i a n palynoflora o f this region. This paper will present interpretations o f p a l a e o ecology and depositional environments based on palynomorph-assemblagecharacteristics, quantitative data and palynofacies. The different assemblage characteristics and datings are outlined, based u p o n the occurrence o f selected taxa and quantitative data. Both cores are a m m o n o i d - d a t e d and are correlated to the Keyserlingites subrobustus, Lenotropites caurus (7323/07-U-04) and Anagymnotoceras varium (7323/07-U-01) Zones (Wolfgang Weitschat, written c o m m u n . , 1 9 8 6 ) a n d c o m p a r e d with the recent a m m o n o i d compilation by M o r k et al. (1989) (Fig.4). The outlined stratigraphic range o f the p a l y n o m o r p h s is one o f the first d o c u m e n t a t i o n s from Lower to Middle Triassic sediments in the Barents Sea region and will therefore prove valuable for future palynostratigraphic studies and correlations within the Barents Sea region. Various palyno-stratigraphic investigations have been carried out on the Triassic succession, mostly

~) 1991 Elsevier Science Publishers B.V. All rights reserved.

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P A L Y N O L O G Y AT T H E SVALIS D O M E

TABLE I Core hole key data LOCATION Year drilled

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concerned with records from limited intervals of the Triassic stages. For the Alpine Triassic, a set of preliminary range-charts showing the stratigraphical distribution of selected species was published by Visscher and Brugman (1981). Recent unpublished theses (Mangerud 1988; Romuld, 1988) and published investigations (Hochuli et al., 1989: Mork et al., 1990) in the Triassic sequences

of the present Arctic regions show that due to different palaeo-climate conditions, some of the important genera recorded in the Alpine region are only rarely present or absent in the Arctic. The stratigraphic range of many species is so far incompletely known. Hochuli et al. (1989) presented the Triassic biostratigraphy of the Barents Sea region based

202

G. MANGERUD AND A. ROMULD

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7323/07-U-04

Fig.4. Biostratigraphic correlation chart c o m p a r i n g a m m o n i t e zones of Svalbard and the Sverdrup Basin. Stratigraphic core position is shown. Time scale is based on Harland et al. (1990). A m m o n i t e correlation is based on M~rk et al. (1989).

PALYNOLOGYATTHESVALISDOME on material from outcrops in Svalbard as well as material from the Barents Sea. They differentiated 15 palynological assemblages, A to P. The two Spathian and Anisian assemblages recorded at the Svalis Dome are here discussed in relation to these palynozones and the established ammonoid zones. A more extensive presentation of all data including seismic interpretation, sedimentological, macrofossil and palynological documentation will soon be presented.

Materials and methods Palynomorphs from 79 core samples are investigated. All samples are referred t o core-depth. The preservation of the palynomorphs varies, but is generally good. The illustrated specimens are housed in the collection of Paleontologisk Museum in Oslo and given PMO numbers. Reference material is stored at IKU. All coordinates refer to England finder, The samples were prepared in the biostratigraphical laboratories of IKU, using standard palyno-

203 Ammonoid correlation Established ammonoid zones have been defined for the Early and Middle Triassic in Svalbard (Tozer and Parker, 1968; Korchinskaya, 1972; Weitschat and Lehman, 1978, 1983) and in the Sverdrup Basin (Tozer, 1965, 1967) and correlated throughout the Arctic by Mork et al. (1989) (Fig.4) and with Arctic U.S.S.R. by Weitschat and Dagys (1989). The macrofaunas recorded in the present cores allow direct biostratigraphic correlation with these on-shore areas. Here, all the data from the two discussed cores are summarized based on preliminary studies by Wolfgang Weitschat (University of Hamburg).

Core 7323/07-U-04

use of a mild oxidative (10% HNO3) treatment to remove pyrite. Approximate quantification of different constituents was estimated visually.

The presence of ammonoids Keyserlingites sp. and Svalbardiceras sp. indicates a correlation with the Keyserlingites subrobustus Zone for the lower part of this core. This zone is recognized in Svalbard and in the Sverdrup Basin and is assigned to the late Spathian. From above 100 m and upwards in this core the deposits contain Grambergia sp. and Lenotropis sp. indicating a correlation with the Lenotrop& caurus Zone. This zone is also recognized in Svalbard and in the Sverdrup Basin and is assigned to the Early Anisian. From ammonoids it is evident that the SpathJan Anisian boundary is penetrated in this core, but there is left an interval of about 8 m (106-98 m) where faunal evidence is missing within which the Spathian-Anisian boundary must be located.

Lithology

Core 7323/07-U-01

logical techniques. Semi-quantitative analyses are based on the counts of about 200 specimens per sample. Palynofacies analyses were carried out using sieved, unoxidized residues. Where remnant minerals dominated the sieved material, the organic residues were separated by ZnBr 2 after the

The lower part of core 7323/07-U-04 consists of dark grey, silty shale with graded medium grey siltstone laminae (Fig.5). Nodules and beds of calcite, phosphorite, pyrite and dolomite are present. It is overlain by medium dark grey silty claystone, continuing into the lower part of core 7323/07-U-01, which also contain graded siltstone and sandstone laminae. An abrupt change to the overlying bioturbated siltstone with common siderite-cemented, graded siltstone and sandstone beds, occurs between 106 and 107 m in this core (Fig.5).

An abundant ammonoid fauna with Anagymnotoceras sp. and Amphipopanoceras sp. was recorded, indicating that the recovered succession can be related to the Anagymnotoceras varium Zone. This zone is recorded in Svalbard, in Siberia and in the Sverdrup Basin and is assigned to the Middle Anisian. Palynostratigraphy and age Our oldest palynological assemblage is dominated by marine palynomorphs of little strati-

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graphic value. The regular presence of cavate spores including Densoisporites nejburgii characterizes these deposits compared to the overlying assemblage (Fig.8), where it only occurs rarely in the lower part of the Middle Anisian strata. The last appearance of Lundbladispora obsoleta is also within this assemblage. Further, the following species with restricted ranges in the Alpine region are recorded: Cvclotriletes triassicus, Cyclotriletes pustulatus, Hexasaccites muelleri and C),cloverrutriletes presselensis. The latter is known as a late Spathian marker species in the Alpine region (Visscher and Brugman, 1981). The base occurrence of Jerseyiaspora punctispinosa is recorded within this assemblage. According to Hochuli et al. (1989) the regular occurrence of cavate spores is a characteristic feature of their assemblage M. Last occurrences of Punctatisporites Jungosus and Rewanispora cf. vermiculatus in the late Spathian strata are mentioned by Hochuli et al. (1989), but these species are not observed in the assemblages from the Svalis Dome. The base range of the species Succinctisporites grandior, which according to Hochuli et al. (1989) is within assemblage M, is not recorded at the Svalis Dome. Following Scheuring (1970)Succinctisporites grandior is considered to be synonymous with Illinites spp., which we recorded rarely in core 7323/07-U-04. The records of Cyclotrih'tes presseh, nsis at the Svalis Dome are a characteristic feature of assemblage M. Range charts (Figs.6, 7) show the ranges of all recorded species, Hochuli et al. (1989) proposed a general Spathian age for their assemblage M. At the Svalis D o m e the palynological assemblage corresponds to the late Spathian Kevserlingites subrobustus Zone. The base of this assemblage is not estab-

205

lished, but we provisionally regard assemblage M to be of late Spathian age. Our youngest assemblage is dominated by marinepalynomorphs and bisaccate pollen. The quantitative palynological composition is clearly different in Spathian and Anisian sediments, but the intervening interval with missing faunal evidence, shows a gradual palynological transition. Cavate trilete spores become a minor group, while cavate monolete spores mostly Aratrisporites, become an important group during the Anisian. The Angustisulcites, Triadisporaand lllinitesgroups are more diverse and are regularly present compared to the assemblage below. The species Dyupetalum cf. vicentinense is restricted in range. This species is first described from the Upper Anisian of the southern Alps (Brugman 1983) and is one of the Anisian marker species of the Alpine Triassic of Europe (Visscher and Brugman, 1981). Species with first occurrence in this assemblage are Asseretospora gyratra and Anapiculatisporites spininger, the former is known to have its oldest appearance in Anisian strata of Arctic Canada (Fisher, 1979). The latter is not recorded before the Ladinian by Fisher (1979) and is not seen in older sediments in the Barents Sea area. Species with last occurrences are Densoisporires nejhurgii and Endosporites papillatus, the latter was used as a Scythian marker species by Visscher and Brugman (1981), but seems to extend up in the Anisian in the Barents Sea area. Densoisporites nejburgii is often very common in Spathian strata (e.g., Balme, 1970; Fisher, 1979), but its top occurfence seems to be within the Middle Anisian. At the Svalis D o m e this last assemblage is recognized within Early and Middle Anisian ammonoid zones Lenotropites taurus and Anagymno-

PLATE I Selected palynomorphs. All magnifications approx. × 500. [. Raistrickiapuncti~spinosaslide 131.01A, UI9/I, PMO number: 121.757 2. Raistrickiapunctispinosa slide 99.01 ox.2, J23/3, PMO number:121.758 3. Cycloverrutriletespresselensis slide 127.00 0xl, C26/4 PMO number: 121.759 4. Cyclotriletespustulatus slide 126.02A, X21/2, PMO number: 121.760 5. Endoq~oritespapillatus slide 124.1 ox2, XI5/I, PMO number: 121.761 6. Dyupetalumcf. vicentinense slide 104.01 ox3, R27/4, PMO number: 121.762 7. Cordaitinagunvalensis slide 97.01 oxl, W17/4, PMO number: 121.763

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EPHEDRIPITES SPP. VERRUEOSISPDR]TE$ MORULAE K L A U $ 1 9 6 0 DICTYOTIDIUM TENUIORNATUM EISENACK 1955 C O N V E R R U C O S I S P O R I T E $ C A M E R O N I I {OE J E R S E Y ) P L . & D E T ' 6 S LUECKISPORITES JUNIOR KLQUS 1960

R~)MUI D

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .FALCISPORITES . KEUPERIANUS PAUTSCH I 9 7 I BRLTISPHQERIDIU~ SPP. ....................................................................... PTEROSPERMOPSIS SPP. ....................................................................................... CONBQCULATISPORITES S P P . VITREISPORITES PRLLIDUS (REISINOER) NILSSON 1968 TRIADISPORA OB5CURA SCHEUR|NG 1970 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GRBNUL@TISPORITES .. 5PP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .PLATYSBCCU$ .. 5PP. ................................................................. GORDONISPORA LUBRICA (ORLOHSKA-Z~OLINSKA)V.D.EEM'83 LUNATISPORITES NOVIAULENSI5 [LESCHIKI SCHEURING 1970 PUNCTQTISPORITES 5PP. .................................................................... KRAEUSELISPORITES SPP. ........................................................... LESCHIKISPORIS QDUNCUS ELESCHIK] POTONIE 1958 PROTODIPLOXYPINUS SPP. LUNQTISPORITE$ SPP. FALCISPORITES S P P . STRIQTOABIEITES BALMEI {KL~US) SCHEURINO 1978 ......................................................................... PEROTRILETES SPP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .PROTODIPLOXYPINU$ SITTLERI [KLAUS) SCHEURING 1970 CYCQDOPITES S P P . CALAMOSPORR SPP. TQSMQNITES SPP. TODISPORITES MINOR CDUPER 1968 QRRTRISPORITES SCQBR~TUS K L Q U $ 1960 QLISPORITES MICRORETICULATUS REINHQRDT 1964 MICRYSTRIDIUM SPP. VERYHACHIUM SPP. LEIOSPHQEIDIUM SPP. QLISPORITE$ SPP. BRATR[SPORITES MACROCAVBTUS BJQERKE ~ MANUM 19~3 'TRIADISPORA SPP. QRQTRISPORITES SPPKRRUSELISPORITE~ C U S P I D U 5 BRLME STRIBTOABIEITES MULTISTRIRTU5 HART 1964 .................................................................................................ENDOSPDRITES PRPILLRTU5 JRNSONIUS 1952 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OENSOISPORITES .. NEJBUROII (SCHULZ) BALME 1970 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .TRIRDISPORR AUREA 5CHEURING 1970 ......................................................................................... UVAESPORITES SPP. ................................................................................................. PODOSPORITES ANICU5 SCHEURING 19~0 ....................................................................................... A N O U S T I S U L C I T E S ORANOIS (FREUOENTHAL) VISSCHER 19gS ............................................................................. nCANTMOTRILETE5 S P P . ............................................................................................... PEROTRILETES 5 P P . ........................................................................................... T O O I S P O R I T E 5 CINCTUS {MALJNWKINA] O R L O N S K A - Z N O L I N S K ~ ' 7 1 ....................................................................................... CONVERRUCOSISPORITE$ S P P . LUNATISPORITE$ ACUTUS {LESCHIK] SCHEURING 1970 ........................................................................... LYCOPODIA[IEDITES $PP. CY~ATHIOSPHAERAE SPP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ANGUSTISULCITES KLAUSI! FREUOENTHAL 1964 .................................................................. DELTDIDOSPORQ MINOR [COUPER) POCOCK ]gTO ............................................................ ARATRISPORITES PQLLETAE (KLQUS) SCHULZ 19~7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PROTODIPLOXYPINUS . GRQCILIS (PQUTSCH] SCHEURING 1970 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .RETICULRTISPORITES .. SPP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VERRUCOSISPORITES 5PP.

GORDONISPORR .............................................................. ............................................................

FOSSULRTA

(BRLMEI

VAN DER EEM 1983

LUNATISPORITE5 PELLUCIDUS IGOUBINI B~LME DELTOOISPORR SPP. ILLINITES CHITONOIDES K L A U S 1964

19~0

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .TYTTODISCUS . SPP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .RRBTRISPORITE5 . TENU|SPINOSU5 PLRYFORD ]955 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .TRIRDISPORR .. MODESTR $CHEURING 1970 ............................................................ BRCULATISPORITE5 SPP. JERSEYIBSPOR£ PUNCTISPINOSR KQR. KIESER & JRIN 1982 @SSERETOSPORQ OYRRTQ [PLAYF.&OETTM.] SCHUURMRN 197? ........................................................................... RLISPORITES GRRUVOOELI] KLAUS 1954 ................................................................................. QCQNTHOTRILETES SPP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .CHORDASPORITE5 . VOLTZIRFORMIS VISSCHER 196~ ............................................................. CONERVISPORITES SPP. ........................................................................................ TRIPLEXISPORITES PLAYFORDII {DE JERS.&HQ~[L.)FOSTER'?9 ..................................................................... TRIADISPORA CR~SSA KLAUS ]954 ................................................................................ PUNCTR~OSPDRITES SPP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .TRIADISPOR£ . PLIC~TR (KLRUS] PLAYFORO & DErTMANN 1965 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MICRORETICULATISPORITES . SPP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .D .Y . UPETQLUM CF. VICENTINENSE BRUOMAN ]983 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .NEORRISTRICKIA . 5PP. ...............................................................................~CANTHOTRILETES VBRIU5 NILSSON 1958 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .CORD~IT]NQ . MINOR (PAUTSCH) PRUTSEH 1973 ........................................................................... CUCULLISPORB 5PP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CYCLOTRILETES OLIOOGRANIFER MAEDLER 1964 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . KRQEUSELISPDR]TES .. QPICULQTUS JANSONIUS )962 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .PROTODIPLOXYPINU6 FASTIDIOIDES {JANSON.~HQRRINGT.'?4 .................................................... RNAPICULQTISPORITES S P P . ........................................................... STEREISPOR]TES SPP. ..................................... DELTOIDOSPORA RUSTRALIS {COUPER) POCOCK Ig?O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ACCINCTISPORITES CIRCUMDATUS {LESCHIKI JQIN 19G8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OSMUNACIEDITES SENECTUS BALME 1983 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .KRREUSELISPORITE$ PUNCTBTU5 JBNSONIUS 1962 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .APICULRTISPORITE5 5PP. ............................... OELIOIDOSPORA CONCQVUS (8OLffHOVITINA) DETTnRNN 1 9 6 3 CORDRTINA OUNYALENSI5 (PANT ~ SRIVRSTRVRI BALME 1970 . . . . . . . . . . . . . . . . . . . . . . . . . . TODISPORITE5 ~BJOR COUPER 1958 . . . . . . . . . . . . . . . . . . . . . . . ILLIN|TES MELANOCORPUS RLAU5 1964 . . . . . . . . . . . . . . . . . . . . . . . . LIMITISPORITES SPP. . . . . . . . . . . . . . . . . . . . CBLAHOSPORQ TENER {LESCHICK) MQEDLER ]964 . . . . . . . . . . . . . . . . PROTOOIPLOXYPINUS POTONIE (MAEOLERI SCHEURINC [q?O

209

P A L Y N O L O G Y A T T H E SVALIS D O M E

toceras varium ammonoid zones. Assemblage M, recorded within the late Spathian ammonoid zone, restricts the assemblage downwards. Hochuli et al. (1989) assigned the palynological assemblage L to the late Spathian to Middle Anisian. The assemblage described corresponds to assemblage L, but is of Early to Middle Anisian age.

Palynomorph assemblages The Late Spathian palynomorph assemblages recorded from the lower part of core 7323/07-U04 are dominated by marine taxa, with specimens such as Tasmanites spp. and Micrhystridium-Veryhachium group equally well represented (Fig.8). Cvmatiosphaera and Pterospermopsis are only present in lower numbers. Lunatisporites dominates the bisaccates, while the proportion of Striatoabieites increases towards the Early Anisian (Fig.8). Non-striate bisaccates like Alisporites are rare. Spores are present in all samples, representing an average of about 12% through the late Spathian. Most species are represented by few specimens, only Densoisporites, Verrucosisporites and Aratrisporites are uniformly present, The Anisian assemblages represented in the upper part of core 7323/07-U-04 and in core 7323/07-U-01 are dominated by bisaccate pollen, which represent about 45% of the total microflora, Although the striate group is the most numerous, alete bisaccate pollen like Alisporites contribute to an average of 5%. The marine microflora which constitutes about 35% of the total assemblage shows a sudden decrease corresponding to a level between 106 and 107 m in core 7323/07-U-01 (Fig.5). At the same level a significant increase in spore content occurs, in particular the number of species Aratrisporites (Fig.8). The total amount of bisaccate pollen shows no change, but monosaccate pollen becomes a regular part of the microflora. Seen in relation to the change from shale to siltstone, this relative increase of spores indicates a shallowing or higher energy environment. This is also seen from the reduction in number of marine specimens above the same level, In conclusion, the two cores contain rich and

diverse terrestrial and marine palynomorph assemblages.

Palynofacies and depositional environment A four-fold subdivision of the acid-resistant organic matter is used. The terrestrial components are divided into liptinitic and wood/charcoal groups. The marine components include acritarchs and marine algae, while the amorphous group is composed of structureless organic matter. Relative amounts of amorphous, marine, liptinitic and wood/charcoal organic matter are plotted against total organic carbon data (Fig.5). The figure also includes the lithological log and the relative distribution of pollen, spores and marine plankton.

Core 7323/07-U-04, Late Spathian Early Anisian Amorphous material dominates the organic rich interval from the base up to about 104 m (Fig.5). The average total organic carbon (TOC) content in this interval is 3.6%, with a maximum of 8.8%. Rich assemblages of marine species are recorded, including abundant Tasmanites. Below 125 m small, unidentified cysts and small algae are cornmon. These silty shale deposits are believed to represent a marine dysoxic, even anoxic environment. From 104 m up to 95.15 m the liptinitic content is higher, but the amorphous matter is still dominant. Total organic carbon values are between 1% and 4%, with the section above 98 m averaging 1.5% in organic richness. Bisaccate pollen types increase quantitatively and Tasmanites are still common. As below, the deposits represent a marine dysoxic or anoxic environment, but show an increased input of terrestrial organic matter. The change in palynofacies coincides with the Spathian Anisian boundary.

Core 7323/07-U-01, Middle Anisian Amorphous material dominates the interval from the base of the core up to about 107 m. At three levels increased terrestrial input resulted in a relatively lower amorphous content with correspondingly low TOC values (Fig.5). These samples

210

G. MANGERUD

AGE (TRIASSIC LATE SPATHIAN Sample no. Dictyotidium spp.

,-'//"

/ / " EARLY I ANISIANI

AND

A. R O M U L [ )

MIDDLE ANISIAN

~ ~ ~ ~ ~ ~ o ~) ~-c4 691 3- r-~

Cymatiosphaera~:spp. -

-

//[~

.,.._.

27VeryhachiUmspp. % ~8:9.~

3O -

Tasmanites

spp. %

2~•

~8-

3bMci~ rhys% trd iu i m18: 2s41'~ 2.6. Striatoabieites ~2 multistriatus

p,~ ~ p , ~ , /K

• .

--

~r--T---m~

/1X

.,¢,

IXV/ I " k r ~ I Nh---t-.-,

Lunatisporites complex Densoisporites nejburgii % Cycadopites spp.%

~

. . . . ~

.

~ _J--~..._-.

36 33 30 27

Aratdspodtes

complex

Triadispora complex

~4

1 5 12 2~

11i

Fig.& F r e q u e n c y d i s t r i b u t i o n o f the m o s t c o m m o n species ( c o m p r i s i n g m o r e t h a n 3 % of the microflora in m o r e t h a n one sample).

may represent very thin storm deposits. Rich assemblages dominated by bisaccate pollen types and marine plankton are recorded throughout the interval. This type of palynofacies characterizes dy-

soxic or anoxic marine environments, interrupted by periods of oxic conditions. Above 107 m terrestrial input predominates (Fig.5) and bisaccate pollen and spores dominate

PALYNOLOGY AT THE SVALIS DOME

the assemblages, which are characterized by abundant Aratrisporites spp. Despite a decrease of marine plankton relative to terrestrial palynomorphs, there is an increased marine palynofacies component. This might be due to larger size of the acritarchs, although the number of specimens present i n t h e s e d i m e n t is l o w e r . W o o d material, including charcoal, represents up to 60% of the organic material in some samples. This is characteristic for oxygenated environments with high terrestrial input. The boundary between the two palynofacies in core 7323/07-U-01 is sharp, and follows the change from shaly to silty lithology. A marked drop in r e l a t i v e s e a l e v e l is postulated o n t h i s e v i d e n c e .

Palaeoecological interpretations The Triassic Period had a stable climate with a wider tropical belt than at present (Frakes, 1979) and the Middle Triassic Epoch was generally characterized by being warm and dry. Due to northwards continental drift during the Triassic, the Svalis Dome area had moved to about 50°N in the Early/Middle Triassic and the Barents Sea area had gained a humid climate in the Spathian/ Anisian time (Steel and Worsley, 1984). A humid belt surrounding the Arctic Ocean in this period is also suggested by Parrish et el. (1982). Their atmospheric circulation models were, however, based on a land configuration of a nearly entirely assembled Pangea in the earliest Triassic. According to later reconstructions by Embry (1989), a northern separated continent was present, making the model less valuable for the Arctic area. The recorded palynomorph associations reflect, however, a moderately, humid climate according to the principles of Visscher and Van der Zwan (1981). The palynomorph assemblages have a slight dominance of hygrophytic elements (Visscher and Van der Zwan, 1981) (Fig.9). Included in this element are monosulcate pollen and spores. Trilete, cavate spores of the Densoisporites type were widespread over the area from western Europe to China associated with the lycophyte Pleuromeia. Aratrisporites occurred worldwide (Meyen, 1987). There is a change from Densoisporites dominance

2[1

Core 7323/7-U-04

O/o 5 o 40 ~ 3o 20 10 0

%

~

5oq 40 30 20 ', 10 0

A B C D'E F 13 H

A B C D E F G F

138.62 100 metres

100 95.15 metres

Core7323/7-U 01

%

5oq 40~ 30 2o~ 10

~ ~

0

',

%

5o 40 30 20 10 0

A B C D E F (3 H

Interval 126.90-107 metres

A El C D E F G H

106-93.75metres

o

ml A. Trilete and monoleteacavatespores ~ B. Trilete cavatespores

o,,,i c Aratrisporites group ev~ D. Monosuleate pollen grains

F. Taeniatebisaeeatepollengrains G. Triletebisaccatepollen

grains

H. Monosaccatepollen grains

o

ii

Fig.9. Relative frequency histograms showing the relationships

betweenhygrophytic and xerophytic elements. to dominance of the Aratrisporites group within the spores across the Spathian/Anisian boundary. Both groups may represent a mangrove/swamplike type of flora. It is not known with certainty whether the alete, bisaccate pollen group which quantitatively is so important, belongs to the hygrophytic or the xerophytic flora element or both (Visscher and Van der Zwan, 1981). The xerophytic element includes striate bisaccate pollen, Triadispora, and monosaccate pollen. A well drained soil would generally contribute to a xerophytic aspect. In this case a significant part of the xerophytic elements in these deposits is represented by taeniate, bisaccate pollen types, many of them produced by conifers. Triadispora, which has been associated with the conifers Albertia and Voltzia (Grauvogel-Stamm, 1978), dominates some intervals and suggests, together with the taeniate bisaccate group, long distance transport from a dry high-land flora. This is related to the "Neves" effect (Traverse, 1988)where the coniferous vegeta-

212

tion in an upland zone produces pollen which are deposited and dominate marine environments far from the coast. The different palaeoecological settings are reflected by quantitative variations in the palynoflora between the two main litho-facies represented by shale-claystone facies through core 7323/07-U-04 and lower part of core 7323/07-U01 and siltstone in the upper part of the latter, The quantitative differences in palynomorph distribution between the two lithofacies are therefore interpreted as mainly deposition-controlled and do not reflect real differences in the original flora. The presence of marine macrofossils, acritarchs and prasinophycean algae throughout the sequence is evidence of marine depositional environment, The two cores are interpreted as representing a regressive development, based on the change towards more terrestrially dominated palynofacies, the general lithological coarsening upwards trend and the change in quantitative distribution of palynomorphs from marine dominance towards a spore dominance. Palaeogeographic reconstructions show a shallow shelf formed upon the edge of the Eurasian platform between the Laurentian Shield, the Baltic Shield and the Uralian front (Fig.10). The Svalis Dome was situated close to Greenland, but on the Barents Shelf a general west/northwest progradation of the shelf edge took place during the Anisian. The spore dominated interval supports short transport from the vegetation area, but we have no evidence from which area the palynomorphs were transported.

Stratigraphic discussion Lower and Middle Triassic deposits outcrop on most land areas surrounding the Barents Shelf. For Svalbard the Triassic stratigraphy was outlined by Buchan et al. (1965) and revised by Mork et al. (1982). For the Lower and Middle Triassic the Sassendalen Group was defined as a mainly shale and siltstone sequence occurring between the distinctive Permian Tempelfjorden Group below and the Kapp Toscana Group above. All stages including Spathian and Anisian, are present in this succession. The age assignation by Buchan et al. (1965) and Mork et al. (1982) was based on extensive palaeontological literature and on provi-

G MANGERUD

AND A R~MULI)

sional identifications of specimens collected by the Cambridge expeditions. Recent work by Mork et al. (1990) also reports palynologically dated Lower and Middle Triassic deposits from the Urd and Skuld Formations on Bjornoya, but only sparse evidence of Spathian and Anisian deposits are documented. A condensed sequence separating the two units is interpreted as being of undifferentiated (?early) Middle Triassic age. For the Barents Shelf little information has been released. In the Hammerfest Basin (well 7120/122) Jacobsen and Van Veen (1984) reported 1500 m of Triassic clastic rocks which they subdivided into five lithostratigraphical units mainly corresponding to the subdivisions on Svalbard. Age determinations were based entirely on palynological evidence from side wall cores, but their fossils are not documented. Their unit 4 correlates with the cored interval presented here, and is of Spathian to Anisian age. Their unit 3 and lower part of unit 4 correlate to the Tvillingodden Formation at Svalbard, while the upper part of their unit 4 resembles the Bravaisberget Formation described from western Svalbard. Unit 4 of Jacobsen and Van Veen (1984) comprises parts of the Klappmys and Kobbe Formations, including a break in sedimentation between the two formations at the Spathian-Anisian transition. A formal lithostratigraphy for the Barents Sea was later established by Worsley et al. (1988), based on the same well (7120/12-2). On northern Greenland, in the Wandel Sea Basin, Sassendalen Group equivalents occur in Parish Bjerg and Dunken Formations (Hfikansson and Stemmerik, 1984). The lower part is undated, but the upper part is of Early and Middle Anisian age (Hfikansson and Heinberg, 1977). In the Sverdrup Basin the Triassic deposits are dated on ammonoid evidence (Tozer, 1961, 1967). As emphasized by M~rk et al. (1989) and Embry (1989) the similarities between Svalbard and the Sverdrup Basin are striking, despite the separated locations on different plates. Embry also draws correlations to northern Alaska. The upper part of the Bjorne Formation in the Sverdrup Basin correlates w i t h t h e S t i c k y K e e p / T v i l l i n g o d d e n F o r mations on Svalbard, while the Murray Harbour

PAI.YNOLOGY & l THE SVALIS DOME

LEGEND ~ Land, non - d e p o s i t i o n

~

213

~

Deltaicto ~,...',.;::4 m a r i n e s a n d s

Continental clastics, ~ i a r i n e molasse

shales

Fig. 10. Early and Middle Triassic palaeogeography. The Svalis Dome is marked by arrow, (Modified from Dor& in press).

Formation of the Sverdrup Basin correlates with the Botneheia Member (Embry, 1989).

ranges can be used to date these deposits to late Spathian to Anisian.

Conclusions

Two distinct palynological assemblages can be calibrated to a late Spathian ammonite zone (Keyserlingites subrobustus) and an early (Lenotropites taurus) Middle Anisian (Anagymnotocesvarium)

The data presented from the Svalis D o m e show that distinctive palynomorphs with restricted

214

G, MANGERUDAND A. ROMULD

ammonite zone, As on Svalbard, no faunal evidence of the earliest Anisian is recorded. The two

Acanthotriletes varius Nilsson 1958 Accinctisporites circumdatus (Leschik) Jain 1968 Alisporites spp.

palynological assemblages correlate well with assemblages M and L of Hochuli et al. (1989).

Alisporites grauvogelii Klaus 1964 Alisporites microreticulatus Reinhardt 1964 Anapiculatisporites spiniger (Leschik) Reinhardt 1961 Anapiculatisporites spp. Angustisulcites gorpii Visscher 1966 Angustisulcites grandis (Freudenthal) Visscher 1966 Angustisulcites klausii Freudenthal 1964 Aratrisporitesmacrocavatus Bjaerke et Manum 1977 Aratrisporites scabratus Klaus 1960 Aratrisporites tenuispinosus Playford 1965

- T h e palynofacies is dominated by amorphous organic matter characteristic of deposits in dysoxic to anoxic environment, normally giving a good source rock potential for hydrocarbons. An interval in the uppermost part of the cored section shows a change to more oxic conditions, reducing the source rock potential. A moderately humid climate is postulated on the basis of the slight dominance of palynomorphs belonging to a hygrophytic element. The relatively high frequency of palynomorphs considered to belong to a xerophytic element is interpreted as representative of an upland flora.

Aratrisporites spp.

Aratrisporites palettae (Klaus) Schulz 1967 Aratrisporitesfimbriatus (Klaus) Playford et Dettmann 1965 Asseretospora gyrata (Playford et Dettmann) Schuurman 1977 Baculatisporites spp. Baltisphaeridium spp. Brachysaccus spp. Bharadwajispora labichensis Jansonius 1962 Calamospora spp. Calamospora tenet (Leschik) Maedler 1964

Chordasporites voltziaformis Visscher 1966 Conbaculatisporites spp.

On lithological, palaeontological and palynological evidence the cored deposits from the Svalis

Concavisporites spp. Converrucosisporites spp.

Dome area can be correlated to the Sticky Keep and Botneheia Members of the Barentsoya Formation on Svalbard. The lithological similarities were reported by M~rk et al. (1989).

mann 1965

Acknowledgements The authors would like to thank Atle M~rk and Tom Bugge for comments and helpful suggestions on the manuscript. Special thanks are due to Jorunn Os Vigran for many helpful discussions throughout the investigation. Thomas Leslie Leith was responsible for organic geochemistry, Geir Elvebakk made the core logs and Wolfgang Weitschat determined the ammonoids. Thanks are also expressed to Inger Lisbet Berg and Ingrid Brandslet for preparing the figures and to Ellen M. Solberg for assistance with the manuscript. We are also grateful to IKU for support to publish this paper, and to the companies which economically supported the Shallow Drilling Project, 1986.

Appendix List of species

Acanthotriletes spp.

Converrucosisporites cameronii (de Jersey) Playford et DenCordaitina minor (Pautsch) Pautsch 1973

Cordaitina gunyalensis (Pant et Srivastava) Balme 1970 Cucullispora spp. Chordasporites spp. Corisaccites spp. Cycadopites spp. Cyclogranisporites spp. Cyclotriletes spp. Cyclotriletes oligogranifer Maedler 1964 Cyclotriletes pustulatus Maedler 1964 Cyclotriletes triassicusMaedler 1964 Cycloverrutriletespresselensis Schulz 1964 Cymatiosphaera spp. Deltoidispora spp. Deltoidospora australis (Couper)Pocock 1970 Deltoidosporaconcavus(Bolkhovitina) Denmann 1963 Deltoidospora minor (Couper) Pocock 1970 Densoisporites spp. Densoisporites nejburgii (Schultz)Balme 1970 Dictyophyllidites mortonii (de Jersey) Playford et Dettmann

1965 Dictyotidium spp.

Dictyotidium tenuiornatum Eisenack 1955 Dyupetalum cf. vicentinense Brugman 1983 Discisporites spp. Endosporites papillatus Jansonius 1962 Ephedripites spp. Falcisporites keuperianus Pautsch 1971 Falcisporites snopkovae Visscher 1966 Falcisporites spp. Falcisporites stabilis Balme 1970

PALYNOLOGYAT THE SVALISDOME

Gordonispora fossulata (Balme) van der Eem 1983 Gordonispora lubrica (Orlowska-Zwolinska) van der Eem 1 9 8 3 Granulatisporites spp. Hexasaccites muelleri Reinhardt et Schmitz 1965 lllinites chitinoides Klaus 1964 lllinites melanocorpus Klaus 1964 lllinites spp. Jerseyiaspora punctispinosa, Kar, Kieser et Jain 1972 Kraeuselisporites apiculatus Jansonius 1962 Kraeuselisporites punctatus Jansonius 1962 KraeuselLworites cuspidus Balme 1963 Kraeuselisporites spp. Lapposisporites armatus Visscher 1966 Leiosphaeridium spp. Leschikisporis aduncus (Leschik) Potoni6 1958 Limiti,q~orites spp. Lueckisporitesjunior Klaus 1960 Lunatisporites acutus (Leschik) Scheuring 1970 Lunatisporites noviaulensis (Leschik) Balme 1970 Lunatisporitespellucidus (Goubin)Balme 1970 Lunatisporites spp. Lundbladispora spp. Lycopodiacidites kuepperi Klaus 1960 Lycopodiaciedites spp. Micrhystridium spp. Microreticulatisporites spp. Neoraislrickia spp. Nevesisporites limatulus Playford 1965 Nevesisporites spp. Osmundacidites senectus Balme 1963 Platy~'accus papillionis Potoni+ et Klaus 1954 Platy~'accus spp. Podosporites amicus Scheuring 1970 Protodiplox)7~inusfastidioides (Jansonius) Warrington 1974 Protodiploxypinus gracilis (Pautsch) Scheuring 1970 Protodiploxypinuspotoniei(Maedler) Scheuring 1970 Polvcingulatisporites spp. Pretricolpipollenites spp. Protodiploxypinus gracilis (Pautsch) Scheuring 1970 Protodiploxypinus sittleri Klaus 1964 Protodiploxypinus spp. Protohaploxypinus spp. Pterospermopsis spp. Punctatisporites spp. Raistrickia spp. Reticulatisporites spp. Stereisporites spp. Striatoabieites balmei (Klaus) Scheuring 1978 Striatoabieites multistriatus Hart Striatoabieites spp. Striatopodocarpites spp. Tasmanites spp. Thymo.spora spp. TodLworites cinctus (Maljawkina) Orlowska-Zwolinska 1971 Todisporites major Couper 1958 Todisporites minor Couper 1958 Todisporites spp. Triadispora aurea Scheuring 1970 Triadispora crassa Klaus 1964 TriadisTora modesta Scheuring 1970

215

Triadispora obscura Scheuring 1970 Triadisporaplicata (Klaus) Playford et Dettmann 1965 Triadispora spp. Triplexisporites plakfordii (de Jersey et Hamilton) Foster 1979 Tyttodiscus spp. Uvaesporites spp. Verrucosisporites jenensis Reinhardt et Schmitz 1965 Verrucosisporites morulae Klaus 1960 Verrucosisporites spp. Veryhachium spp. Fitreisporites pallidus (Reissinger) Nilsson 1958 l~bltziaceaesporites heteromorpha Klaus 1964

References Balme, B.E., 1970. Palynology of Permian and Triassic Strata in the Salt Range and Surghar Range, West Pakistan. In: B. Kummel and C. Teichert (editors). Stratigraphic Boundary Problems: Permian and Triassic of West Pakistan. Univ. Kansas Dept. Geol. Spec. Publ., 4: 304-453. Brugman, W.A., 1983. Aspects of Early and Middle Triassic palynology. 1. Dyupetalum vicentinense nov. sp. from the Upper Anisian of the Southern Alps. Rev. Palaeobot. Palynol., 39: 47-64. Buchan, S.H., Challinor, A., Harland, W.B. and Parker, J.R., 1965. The Triassic stratigraphy of Svalbard. Nor. Polarinst. Skr.. 135: 1-94. Dot6, A.G., in press. The structural foundation and evolution of Mesozoic Seaways between Europe and the Arctic Sea. In: Development of the Tethyan ocean. Palaeogeogr., Palaeoclimatol., Palaeoecol., Special Issue. (Channell Tansa & Winterer eds.). Embry, A., 1989. Correlation of Upper Palaeozoic and Mesozoic sequences between Svalbard, Canadian Arctic Archipelago, and Northern Alaska. In: J.O. Collinson (editor), Correlation in Hydrocarbon Exploration. Norwegian Petroleum Society. Graham & Trotman, London, pp.89 98. Fisher, M.J., 1979. The Triassic palynofloral succession in the Canadian Arctic Archipelago. Am. Assoc. Stratigr. Palynol. Contrib. Ser., 5B: 83-100. Frakes, L.A., 1979. Climates throughout Geological Time. Elsevier, Amsterdam, 310 pp. Gabrielsen, R., Fa~rseth, R.B., Jensen, L.N., Kalheim, J.E. and Riis, F., 1990. Structural elements of the Norwegian continental shelf. Part 1: The Barents Sea Region. Norw. Pet. Dir. Bull no.6, 33 pp. Grauvogel-Stamm, L., 1978. La flore du gres a Voltzia (Buntsandstein superior) des Vosges du Nord (France). Morphologie, anatomic, interpretations phylogenique et paleogeographique. Univ. L. Pasteur de Strasbourg, Inst. Geol., Mem., 50:1 225. Harland, W.B., Armstrong, R.L., Cox, A.V., Craig, L.E., Smith, A.G. and Smith, D.G., 1990. A Geologic Time Scale. Cambridge University Press, 263 pp. Hochuli, P.A., Colin, J.P. and Vigran, J.O., 1989. Triassic biostratigraphy of the Barents Sea Area. In: J.D. Collinson (Editor), Correlation in Hydrocarbon Exploration Norwegian Petroleum Society. Graham & Trotman, London, pp.131 153.

216 Hfikansson, E. and Heinberg, C., 1977. Reconnaissance work in the Triassic of the Wandel Sea Basin, Peary Land, eastern North Greenland. Gronl. Geol. Unders. Rapp., 85:11-15. H&kansson, E. and Stemmerik, L., 1984. Wandel Sea Basin The North Greenland equivalent to Svalbard and the Barents Shelf. In: A.M. Spencer et al. (Editors), Petroleum Geology of the North European margin, Norwegian Petroleum Society. Graham & Trotman, London, pp.97 108. Jacobsen, V. and Van Veen, P., 1984. The Triassic offshore north of 62 N. In: A.M. Spencer et al. (Editors), Petroleum Geology of the North European margin, Norwegian Petroleum Society. Graham & Trotman, London, pp.317 328. Korchinskaya, M.V., 1972. Biostratigraphy of Triassic deposits of Svalbard. Bull. Can. Soc. Petrol. Geol. Mere., 2: 261-268. Kristoffersen, Y. and Elverhoi, A., 1978. A diapir structure in Bjerneyarenna. Nor. Polarinst. Arbok, 1977, pp.189- I98. Mangerud, G., 1988. Palynomorfer og annet organisk materiale i Midtre Trias (Anis) sediment Ira Barentshavet. Unpubl. thesis, Univ. Trondheim, 102pp. (in Norwegian). Meyen, S.V., 1987. Fundamentals of Palaeobotany. Chapman & Hall, Univ. Press, Cambridge, 432 pp. Merk, A., Embry, A. and Weitschat, W., 1989. Triassic transgressive-regressive cycles in the Sverdrup Basin, Svalbard and the Barents Shelf. In: J.O. Collinson (Editor), Correlation m Hydrocarbon Exploration. Norwegian Petroleum Society. Graham & Trotman, London, pp. ll3 130. Merk, A., Knarud, R. and Worsley, D., 1982. Depositional and diagenetic environments of the Triassic and Lower Jurassic succession of Svalbard. In: A.F. Embry and H.R. Balkwill (Editors), Arctic Geology and Geophysics. Can. Soc. Pet. Geol. Mere., 8:371 398. Mork, A., Vigran, J.O. and Hochuli, P., 1990. Triassic geology and palynology of Bjerneya. Polar Res., 8:141 163. Parrish, J.T., Ziegler, A.M. and Scotese, C.R., 1982. Rainfall patterns and the distribution of coals and evaporites in the Mesozoic and Cenozoic. Palaeogeogr., Palaeoclimatol., Palaeoecol., 40: 67-I01. Romuld, A., 1988. En palynologisk undersekelse av undre,' midtre trias i Barentshavomrfidet. Unpubl. Thesis. Univ. Trondheim, pp.96. (In Norwegian). Scheurmg, B.W., 1970. Palynologische und palynostratigrafische Untersuchungen des Keupers im Bolchentunnel (Solothurner Jura). Schweiz. Palaontol. Abh., 88: 1- 119.

G MANGILRIl) AND A ROMULD Steel, R. and Worsley, D., 1984. Svalbard's post-Caledonian strata - - an atlas of sedimentational patterns and palaeogeographic evolution. In: A.M. Spencer et al. (Editors): Petroleum Geology of the North European Margin. Norwegian Petroleum Society, Graham & Trotman, London, pp.109 135. Sundvor, E., I974. Seismic refraction and reflection measurements in the Southern Barents Sea. Mar. Geol., 16:255 273. Tozer, E.T., 1961. Triassic stratigraphy and faunas, Queen Elizabeth Islands, Arctic Archipelago. Geol. Surv. (7an. Mem., 316:1 116. Tozer, E.T., 1965. Lower Triassic stages and ammonoid zones of Arctic Canada. Geol. Surv. Can. Pap., 65 124. Tozer, E.T., 1967. A standard for Triassic time. Geol. Surv. Can. Bull., 156:1 103. Tozer, E.T. and Parker, J.R., 1968. Notes on the Triassic biostratigraphy of Svalbard. Geol. Mag., 105 (6): 526 542. Traverse, A., 1988. Paleopalynology. Unwin Hymam Boston, 600 pp. Visscher, H. and Brugman, W.A., 1981. Ranges of selected palynomorphs in the Alpine Triassic of Europe, Rev. Palaeobot. Palynol., 34:115 128. Visscher, H, and Van der Zwan, C.J., 1981. Palynology of the circum-Mediterranean Triassic: phytogeographical and paleoclimatological implications. Geol. Rundsch., 70: 625 634. Weitschat, W. and Lehmann, U., I978. Biostratigraphy of the uppermost part of the Smithian stage (Lower Triassic) at the Botneheia, W-Spitsbergen. Mitt. Geol. Pal~.iontol. Inst. Univ. Hamburg, 48:85 100. Weitschat, W. and Lehmann, U., 1983. Stratigraphy and ammonoids from the Middle Triassic Botneheia Em. (Daonella Shales) of Spitsbergen. Mitt. Geol. Pal:iontol. Inst. Univ. Hamburg, 54:27 54. Weitschat, W. and Dagys, A.S., 1989. Triassic biostratigraphy of Svalbard and a comparison with NE-Siberia. Mitt. Geol. Pal/iontol. Inst. Univ. Hamburg, 68:179 213. Worsley, D., Johansen, R. and Kristensen, S.E., 1988. The Mesozoic and Cenozoic succession of Tromseflaket. In: A. Dalland et al. (Editors). A lithostratigraphic Scheme for the Mesozoic and Cenozoic Succession offshore Mid- and Northern Norway. Norw. Pet. Dir. Bull., 4:42 65.