Hans Arne Nakrem

Triassic conodonts from Svalbard and their Boreal correlations

Conodont faunas are described from Triassic sections of Svalbard, and their occurrences are locally correlated with established ammonoid zones. With a synthesis of previous conodont-based publications, the current work presents a taxonomically up-to-date compilation of conodont data for the Triassic of Svalbard that is used to construct a conodont-based biochronology, indexed to the current lithostratigraphic nomenclature. Twenty-eight taxa spanning the earliest Griesbachian to the earliest Carnian are presented in a range chart. The examined conodont faunas are correlated with well-established conodont zonations of the Canadian Arctic, and in turn also form the basis for regional correlations.

New Early Triassic Bryozoa (Trepostomata) from Spitsbergen, with some remarks on the stratigraphy of the investigated horizons

New trepostomatous bryozoan species, Paralioclema winsnesi sp. nov., Paralioclema mariaholmensis sp. nov. and Paralioclema sp. cf. mariaholmensis are described from the Lower Triassic succession of Spitsbergen. The investigated bryozoan faunas are associated with coarse sandstones, calcareous siltstones and shelly limestones. The bryozoan colonies are mostly well preserved in situ , and show limited evidence of transportation. Some zoarial fragments show bioerosion. The conodont species Neogondolella elongata, Ellisonia triassica, Neospathodus dieneri and Neospathodus svalbardensis extracted from the investigated horizons are Dienerian–Smithian in age.

Lower Triassic bryozoan beds from Ellesmere Island, High Arctic, Canada

In the Sverdrup Basin (Canadian Arctic), the Lower Triassic Blind Fiord Formation, comprising siltstone and shale, overlies various Middle to Late Permian (post-Wordian) sedimentary units. This formation is subdivided into three members: the Confederation Point, Smith Creek and Svartfjeld members of, respectively, Griesbachian–Dienerian, Smithian–Spathian and Spathian ages. Lower Triassic bryozoan beds are known from many sections of Ellesmere Island, but have never been studied in detail. During the Early Triassic biotic recovery interval, immediately following the Permian/Triassic extinction event, only one new bryozoan genus evolved in the Boreal region: Arcticopora. The first lower Triassic bryozoan bed appears in the upper part of the Confederation Point Member, and is dated as late Dienerian. Succeeding bryozoan levels occur in the upper Smith Creek Member, and are late Smithian–early Spathian in age. Bryozoan beds occupy a similar stratigraphic position in Spitsbergen. There, they occur scattered in silt to coarse sandstone beds, but also in bryozoan-dominated packstone beds resembling the packstone units in the uppermost part of the Confederation Point Member of Ellesmere Island. Previously, bryozoan-rich beds of Triassic age have not been reported, and the present work fills an important time gap in the bryozoan carbonate database.

Large Onychites (Cephalopod Hooks) from the Upper Jurassic of the Boreal Realm

We report on the discovery of large cephalopod arm hooks (mega−onychites) from the Kimmeridgian and Volgian of Spitsbergen (Agardhfjellet Formation). This includes a largely uncompressed hook in a seep carbonate,with preservation of surface sculpture. We suggest the use of logarithmic spirals as morphological descriptors for the outer part of cephalopod arm hooks, with implications for systematics and functional morphology. Comparison with Upper Jurassic material from Greenland, northern Norway and the North Sea demonstrates a remarkably consistent morphology, which we assign to the same form species, Onychites quenstedti. Considering the relatively small stratigraphic (Kimmeridgian— Volgian) and biogeographic (Boreal) range of this large form, it is likely that it represents a single biological species or genus.

Migrated oil on Novaya Zemlya, Russian Arctic: Evidence for a novel petroleum system in the eastern Barents Sea and the Kara Sea

In this article, we present evidence for the migration of Cretaceous or younger oil into Paleozoic strata on the islands of Novaya Zemlya, Russian Arctic, originating from the surrounding basins of the Barents Sea and the Kara Sea. We thus suggest a novel petroleum system for the greater Barents Sea and Kara Sea regions. Organic geochemical data reveal that medium mature petroleum is hosted in overmature Paleozoic rocks onshore Novaya Zemlya. This petroleum likely migrated from the surrounding offshore sedimentary basins of the Kara and Barents seas into the onshore strata on a broad front, covering 400 km (248 mi) along the archipelago. Thus, the findings describe the remnants of petroleum migration on a regional scale. High maturities of the examined onshore strata (vitrinite reflectance [Ro] of 1.9–4.0% and conodont color alteration index values of 4–6) render the indigenous origin of the medium mature petroleum unlikely. Organic geochemical characteristics of the migrated hydrocarbons lead us to suggest the existence of a hitherto undescribed marine shale source rock with some contribution of terrigeneous organic matter. The 13C isotope values varying within a range of 5 for bulk extracts as well as for individual n-alkanes and isoprenoids suggest isotopic heterogeneity of the organic source facies. The source rock units are inferred to have released hydrocarbons mostly at oil window maturities (higher than 0.6% Ro). The occurrence of n-alkanes and isoprenoids, as well as abundant and partially degraded tricyclic terpanes indicates mixed undegraded and heavily biodegraded oil. This suggests several petroleum charges with varying degrees of microbial degradation. Occurrences of oleanane, high ratios of C28 to C29 steranes and elevated 24-norcholestane and 24-nordiacholestane ratios suggest Cretaceous or Tertiary source rocks.

Lower Permian Bryozoans from Southern and Central Spitsbergen, Svalbard

Bryozoans from the Lower Permian Treskelodden and Wordiekammen formations of southern and central Spitsbergen respectively, Svalbard, have been studied. Twenty species are identified, including one new genus, Toulapora gen. nov., with Toulapora svalbardense as type species and one new species, Ascopora birkenmajeri sp. nov. The taxonomic composition is typical Lower Permian, with species in common with Timan-Pechora and the Urals (Russia) and Ellesmere Island (the Canadian Arctic). Growth habits reflect a moderately to deeper shelf environment.

Ramipora hochstetteri Toula, 1875 (Bryozoa, Cystoporata), from the Permian of Svalbard

ABsTRAcr-This review of the goniocladiid genus Ramipora Toula is based on zoarial morphology. The diagnosis of Ramipora is emended and the type species R. hochstetteri Toula from the Upper Permian of Svalbard is redescribed. Anastomosing secondary branches forming a fenestrated meshwork discriminate Ramipora from other goniocladiids. Descriptions are based on new material collected from the type horizon (Kapp Starostin Formation, Akseloya) and elsewhere in the Svalbard Archipelago, and also on Toulas type specimen. Goniocladiella Nekhoroshev and Aetomacladia Bretnall are herein designated junior synonyms of Ramipora. Some species previously assigned to Ramipora are transferred to Ramiporidra.

Brachiopods from Late Jurassic—Early Cretaceous hydrocarbon seep deposits, central Spitsbergen, Svalbard

Late Jurassic-Early Cretaceous (Late Volgian-latest Ryazanian) rhynchonellate brachiopods are described from eight out of 15 hydrocarbon seep deposits in the Slottsmøya Member of the Agardhfjellet Formation in the Janusfjellet to Knorringfjellet area, central Spitsbergen, Svalbard. The fauna comprises rhynchonellides, terebratulides (terebratuloids and loboidothyridoids) and a terebratellidine. The rhynchonellides include: Pseudomonticlarella varia Smirnova; Ptilorhynchia mclachlani sp. nov.; and Ptilorhynchia obscuricostata Dagys. The terebratulides belong to the terebratuloids: Cyrtothyris? sp.; Cyrtothyris aff. cyrta (Walker); Praelongithyris? aff. borealis Owen; and the loboidothyridoids: Rouillieria cf. michalkowii (Fahrenkohl); Rouillieria aff. ovoides (Sowerby); Rouillieria aff. rasile Smirnova; Uralella? cf. janimaniensis Makridin; Uralella? sp.; Pinaxiothyris campestris? Dagys; Placothyris kegeli? Harper et al.; and Seductorithyris septemtrionalis gen. et sp. nov. The terebratellidine Zittelina? sp. is also present. Age determinations for all but one of the brachiopod-bearing seeps are based on associated ammonites. Five of the seep carbonates have yielded Lingularia similis?, and it is the only brachiopod species recorded from two of the seeps. Other benthic invertebrate taxa occurring in the seeps include bivalves, gastropods, echinoderms, sponges, and serpulid and non-serpulid worm tubes. The brachiopod fauna has a strong Boreal palaeobiogeographic signature. Collectively, the Spitsbergen seep rhynchonellate brachiopods exhibit high species richness and low abundance (<100 specimens from 8 seeps). This contrasts markedly with other Palaeozoic---Mesozoic brachiopod-dominated seep limestones where brachiopods are of low diversity (typically monospecific) with a super-abundance of individuals. The shallow water environmental setting for the Spitsbergen seeps supported a diverse shelf fauna, compared to enigmatic Palaeozoic-Mesozoic brachiopod-dominated seeps.

A Boreal serpulid fauna from Volgian-Ryazanian (latest Jurassic-earliest Cretaceous) shelf sediments and hydrocarbon seeps from Svalbard

ABSTRACT Serpulid polychaete tubes are described from Volgian-Ryazanian sediments (?Pyrgopolon decorata (Stolley, 1912), ?Pyrgopolon aff. nodulosum (Lundgren, 1883)) and four contemporaneous hydrocarbon seep deposits (?Pyrgopolon aff. nodulosum, ?Pyrgopolon sp. A, Propomatoceros sp. A, Nogrobs aff. quadricarinata Münster in Goldfuss, 1831) from Spitsbergen, Svalbard. These are the oldest serpulid tubes yet described from fossil hydrocarbon seep deposits, and comprise the most diverse fossil seep serpulid fauna known to date. The genera Propomatoceros Ware, 1975 and Nogrobs de Montfort, 1808 have their first fossil occurrence elsewhere in the Early Jurassic and then appear in the Svalbard seeps much later. This is the first report of ?Pyrgopolon de Montfort, 1808 from a fossil seep site.

Lower Permian Bryozoa from Ellesmere Island (Canada)

A collection of fossils sampled during the 1898–1902 expedition of theFram to the Canadian Arctic Islands includes abundant bryozoans from the Lower Permian (Artinskian) Great Bear Cape Formation of Ellesmere Island. From this material a new genus with one new species —Nansenopora peculiaris n. gen., n. sp. — as well as three new species —Streblotrypella arctica n. sp.,Phragmophera patricki n. sp. andKallodictyon spinatum n. sp. — are described. Furthermore, the speciesUlrichotrypa ramulosaBassler, 1929 is reported for the first time from the Lower Permian of the Arctic region.KurzfassungGeologische Sammlungen, welche während der Expedition derFram zu den Inseln des arktischen Kanada gesammelt wurden, enthalten zahlreiche Bryozoen aus der unterpermischen (Artinskium) Great Bear Cape Formation von der Insel Ellesmere. Von diesem Material werden eine neue Gattung mit einer neuen Art —Nansenopora peculiaris n. gen., n. sp. — sowie drei neue Arten —Streblotrypella arctica n. sp.,Phragmophera patricki n. sp. undKallodictyon spinatum n. sp. — beschrieben. Außerdem wird die ArtUlrichotrypa ramulosaBassler, 1929 zum ersten Mal im Unterperm aus der arktischen Region festgestellt.