Øyvind Hammer

• Newby, Sean M.; Owens, Jeremy D.; Young, Seth A. & Hammer, Øyvind (2026). Thallium Isotopes Across the Smithian-Spathian Boundary: Evidence for Anoxia Throughout Most of the Early Triassic. Geobiology. ISSN 1472-4677. 24(5), p. e70062–e70062. doi: 10.1111/gbi.70062. Full text in Research Archive
• Smelror, Morten; Gasser, Deta; Domeier, Mathew Michael & Hammer, Øyvind (2026). Reestablishment of an early life shallow marine ecosystem in the Neoproterozoic Gardnos meteorite impact crater (Norway). Palaeogeography, Palaeoclimatology, Palaeoecology. ISSN 0031-0182. 687. doi: 10.1016/j.palaeo.2026.113607. Full text in Research Archive Show summary

  Trace fossils, microbially induced sedimentary structures (MISS), palynomorphs and particulate organic matter (POM) found in post-impact sediments in the Gardnos meteorite crater provide evidence of reestablishment of a Neoproterozoic ecosystem in a shallow marine, littoral environment, with sediments covered by microbial mats. Trace fossils are rare and restricted to horizontal burrows, including Gordia, Helminthopsis, Yichnia and poorly preserved tracks resembling Archaeonassa. MISS and water-escape structures are common and include characteristic features like Aristophycus. The recovered organic walled microfossils Trachysphaeridium laminaritum and Sphaerocongregus variabilis indicate a late Neoproterozoic age for the post-impact sediments. Particulate organic matter in deposits comprise dominantly dark grey to black, highly thermally altered amorphous kerogen and fragments of algal material (TAI ∼ 4, temperature ˃ 250 °C). The trace fossils and MISS are typical of Neoproterozoic shallow marine mat-ground environments which existed prior to the development of Phanerozoic mixed-ground ecosystems.

• Engelschiøn, Victoria Sjøholt; Hammer, Øyvind; Wesenlund, Fredrik; Hurum, Jørn Harald & Mørk, Atle (2025). Palaeoenvironment and new chemostratigraphic markers for the Middle Triassic succession in Svalbard. Norwegian Journal of Geology. ISSN 2387-5844. 105(3), p. 1–45. doi: 10.17850/njg105-3-2. Full text in Research Archive Show summary

  This study presents a detailed analysis of the Middle Triassic Botneheia Formation in Svalbard, integrating sedimentology, geochemistry and palaeontology to understand the depositional environment. Fieldwork was conducted at five localities in central Spitsbergen and Edgeøya, with two additional localities in western Spitsbergen and Bjørnøya for comparison. Three carbon-isotope excursions are identified for the first time in the Botneheia Formation in central Spitsbergen and on Edgeøya—the positive Olenekian–Anisian Carbon Isotope Excursion (OACIE), negative Anisian–Ladinian Isotopic Carbon Excursion (ALICE), and positive Ladinian–Carnian Carbon Isotope Excursion (LICE). It is possible that OACIE is also present in western Spitsbergen and Bjørnøya and that LICE extends to Bjørnøya. We discuss their potential use as regional chronostratigraphic markers, drawing global comparisons. Systematic documentation of body and trace fossils from bulk sediment samples reveals benthic fossils in 153 out of 339 samples, and a higher diversity especially of bivalves than previously assumed for the Botneheia Formation. There are notable differences in benthic diversity and oxygenation between central Spitsbergen and Edgeøya, with lower diversities in the east, associated with more dysoxic conditions. These differences may be linked to the Ural Delta approaching from the east causing algal blooms and haloclines already in the Middle Triassic. The combination of geochemical proxies with fossil assemblages provides a detailed reconstruction of a Boreal Sea seabed during the Middle Triassic and highlights the influence of fluctuating oxygen levels in shaping benthic ecosystems and depositional environments.

• Wang, Siyu; Birgel, Daniel; Nakrem, Hans Arne; Little, Crispin T.S.; Hammer, Øyvind & Kelly, Simon R.A. [Show all 7 contributors for this article] (2025). Sulfate-driven anaerobic oxidation of methane recorded by Lower Cretaceous (Barremian) authigenic carbonate deposits from the Kuhnpasset Beds of Wollaston Forland, northeast Greenland. Palaeogeography, Palaeoclimatology, Palaeoecology. ISSN 0031-0182. 680. doi: 10.1016/j.palaeo.2025.113349. Full text in Research Archive Show summary

  The Lower Cretaceous (Barremian) Kuhnpasset sedimentary sequence of northeast Greenland contains many carbonate deposits in different stratigraphic positions in the area of Wollaston Forland, several of which have previously been identified as having a hydrocarbon seep origin based on their macrofossil content and morphology. Most of the seep carbonates contain complex internal microfabrics, including abundant yellow calcite and banded and botryoidal cement with δ13C values as low as 􀀀 54 ‰. These δ13C values are characteristic of carbonate microfabrics with biogenic methane as the major carbon source and carbonate authigenesis caused by sulfate-driven anaerobic oxidation of methane (SD-AOM). Such 13C-depletion confirms a methane seep origin of most of the Kuhnpasset carbonate deposits. Molecular fossils from the seep carbonates prove methanotrophic archaea were involved in the SD-AOM consortia, based on 13C-depleted 2,6,10,15,19-pentamethylicosane (PMI; δ13C: 􀀀 122 to 􀀀 113 ‰) and the co-eluting crocetane and phytane (􀀀 124 to 􀀀 105 ‰). The carbon source for the Kuhnpasset seeps was biogenic methane with a δ13C value of approximately 􀀀 70 ‰, as calculated from compound-specific δ13C values of archaeal lipid biomarkers. The δ13C values of the biomarkers of sulfate-reducing bacteria, the synthrophic partners of archaea in SD-AOM, including iso- and anteiso-C15/17 fatty acids are less 13C-depleted (􀀀 107 to 􀀀 87 ‰) than the archaeal biomarkers – a pattern known from modern seep environments. Preservation of bacterial fatty acids is rare for Mesozoic seep deposits, revealing excellent biomarker preservation and low thermal maturity of the Kuhnpasset seep deposits. The common isoprenoid hydrocarbon biomarkers of SD-AOM in the Kuhnpasset seep carbonates are accompanied by 13C-depleted isoprenoic acids (phytanoic acid: 􀀀 112 to 􀀀 101 ‰); these compounds are attributed to the early degradation of glycerol diether membrane lipids such as archaeol or sn2-hydroxyarchaeol, which are not preserved in the samples. Similarly, regular PMI-acid (􀀀 120 to 􀀀 107 ‰) probably represents a derivative of extended archaeol or extended hydroxyarchaeol. The molecular fossil inventories in the Kuhnpasset seep carbonates and the predominance of early diagenetic banded and botryoidal cement are characteristic of the dominance of ANME-2 consortia adapted to high methane flux with the sulfate-methane transition zone (SMTZ) positioned at shallow sediment depth. Abundant wood fragments and well-preserved leafy conifer shoots enclosed in the Kuhnpasset seep deposits indicate a shallow marine paleoenvironment of deposition close to the former shoreline.

• Roberts, Aubrey J.; Rucinski, Maciej Roman; Kear, Benjamin P.; Hammer, Øyvind; Engelschiøn, Victoria Sjøholt & Scharling, Thomas Holm [Show all 8 contributors for this article] (2025). Earliest oceanic tetrapod ecosystem reveals rapid complexification of Triassic marine communities. Science. ISSN 0036-8075. 390(6774), p. 727–727. doi: 10.1126/science.adx7390. Full text in Research Archive Show summary

  Tetrapods invaded oceanic environments after the cataclysmic end-Permian mass extinction (EPME), with temnospondyl amphibian to reptile-dominated assemblages succeeding across the Early Triassic [~251.9 to 247.2 million years ago (Ma)]. However, conflicting fossil occurrences, divergence estimates, and stratigraphic time averaging make the tempo of this landmark evolutionary transition uncertain. In this work, we describe an oceanic tetrapod ecosystem from a condensed mid–Early Triassic (early Spathian, ~249 Ma) bone bed on the arctic island of Spitsbergen. Apex predator ichthyosaurians, small-bodied ichthyopterygians, durophagous ichthyosauriforms, semiaquatic archosauromorphs, euryhaline temnospondyls, coelacanths, lungfish, ray-finned fish, and sharks formed an unexpectedly complex trophic network. Comparative diversity analyses further show that heterogeneous marine vertebrate communities were well established by the late-earliest Triassic (Dienerian-Smithian, ~251 Ma) and integrated fully variegate tetrapod niches by ~3 million years after the EPME.

• Kings, Jonathan; Folkow, Lars; Hammer, Øyvind; Kjelstrup, Signe; Mason, Matthew J. & Xiong, Fengzhu [Show all 7 contributors for this article] (2025). A model for maxilloturbinate morphogenesis in seals. PLOS ONE. 20(3). doi: 10.1371/journal.pone.0316669. Full text in Research Archive
• Rojo, Maximo Alfonso; Qviller, Atle Jorstad; Castro, Nélia Sofia Cardoso & Hammer, Øyvind (2024). Trilobite thin section analysis clarifies matrix separation properties . Geological curator. ISSN 0144-5294. 11(9), p. 594–599. doi: 10.55468/gc1474. Full text in Research Archive Show summary

  Mechanical preparation of trilobite and other calcitic fossils in carbonates depends on fossil-matrix separation properties. In this pilot study, thin sections with trilobite fossils from the Ordovician of Norway and the Devonian of Morocco were investigated to identify the mineralogical basis for separation differences, using petrographic microscopy as well as semi-quantitative elemental analysis and element mapping under the scanning electron microscope. The results show that the matrix is composed of fine-grained calcite (CaCO3) together with silicates, i.e., impure limestone with a clastic component. The trilobite specimens are composed of calcite, often in the form of large euhedral crystals. A thin layer of different composition was found along the boundaries between trilobite fossils and their host rock in well-separating specimens. Silica and sometimes barium sulphate were identified in these thin layers. We conclude that partial silicification at the surface of fossils facilitates separation during mechanical preparation.

• Park, Juni; Stein, Holly Jayne; Hannah, Judith Louise; Georgiev, Svetoslav; Hammer, Øyvind & Olaussen, Snorre (2024). Paleoenvironment in the circum-arctic region from the Middle Jurassic to Early Cretaceous: Trace element and stable isotope geochemistry of the Agardhfjellet Formation, Svalbard. Palaeogeography, Palaeoclimatology, Palaeoecology. ISSN 0031-0182. 649. doi: 10.1016/j.palaeo.2024.112333. Full text in Research Archive
• Hansen, Bitten Bolvig; Bucher, Hugo F. R.; Schneebeli-Hermann, Elke & Hammer, Øyvind (2024). Smithian and Spathian palaeontological records of the Vikinghøgda Formation in Central Spitsbergen. Lethaia: An International Journal of Palaeontology and Stratigraphy. ISSN 0024-1164. 57(1). doi: 10.18261/let.57.1.3. Full text in Research Archive Show summary

  Vertebrate and invertebrate fossils from the Smithian (Early Triassic) to the Early-Middle Triassic boundary interval of Svalbard, Arctic Norway have been known for a long time, but have rarely been extensively collected with precise stratigraphical control. We describe new bulk collections from precisely measured sections in the Vikinghøgda Formation in Central Spitsbergen. Accompanying geochemical data provide further constraints on the changes in palaeoenvironments. Species richness of both benthos and nekton remains low throughout the studied interval but reduces to a minimum in the early Spathian, i.e. in the wake of the late Smithian extinction and a probable associated short ice age that straddled the Smithian–Spathian boundary as manifested by a global hiatus in continental shelves. The faunal stratigraphical succession and geochemical data series indicate a regression event in the late Smithian followed by deepening sea level in the early Spathian. This is consistent with a global cooling phase in the late late Smithian that has been previously interpreted as a likely glacio-eustatic episode. The lowermost Spathian is marked by near-absence of benthos, compatible with increased water depth but also possibly linked to the aftermath of the Smithian-Spathian extinction. The lateral expansion of another and younger gap (‘the Marmierfjellet hiatus’ of early or middle Spathian age) is here interpreted as an off-shore condensation horizon generated by the probably highest sea-level stand recorded in the Spathian of Spitsbergen. These hiatuses of opposite origin, as well as the acute selective preservation linked with the low carbonate content of the studied series, have to be factored out as biases when estimating species richness and interpreting palaeo-ecological changes. The study also identifies Early Triassic fossil taxa new to Spitsbergen, in particular Peribositria sibirica and bakevellid bivalves. The orthoceratoids are reviewed, and two distinct taxa are identified at different stratigraphical levels.

• Blattmann, Franziska R.; Schneebeli-Hermann, Elke; Adatte, Thierry; Bucher, Hugo F. R.; Vérard, Christian & Hammer, Øyvind [Show all 8 contributors for this article] (2024). Palaeoenvironmental variability and carbon cycle perturbations during the Smithian-Spathian (Early Triassic) in Central Spitsbergen. Lethaia: An International Journal of Palaeontology and Stratigraphy. ISSN 0024-1164. 57(2). doi: 10.18261/let.57.2.1. Full text in Research Archive Show summary

  The Early Triassic Smithian and Spathian time intervals are characterized by perturbations in the global carbon cycle, fluctuations in sea surface temperature, high turnover rates of marine nekton, and a change in terrestrial vegetation. Despite the importance of this time interval, comprehensive multiproxy investigations from Early Triassic high and middle latitude regions remain scarce due to the difficulty in accessing sections. The objective of this study is to increase our understanding of regional and local palaeoenvironmental and carbon cycle perturbations from a middle Smithian to late Spathian middle latitude section from Central Spitsbergen. Geochemical analyses show an increase in phosphorus and nitrogen just at and above the Smithian–Spathian boundary (SSB). High primary productivity led to increasingly anoxic conditions in bottom waters during the middle and late Spathian, enhancing the preservation of organic matter in the sediments. Anoxic conditions restrain phosphorus remineralization, allowing it to be recycled within the water column. This increase in anoxia is consistent with observations in other Arctic basins, demonstrating larger regional similarities in palaeoenvironmental conditions. The fluctuations in isostatic and eustatic sea levels affected organic carbon sequestration by regulating organic matter mineral interactions via the control of grain size within the sediment. This study demonstrates that local organic carbon sequestration in the Barents Sea shelf during the Spathian was influenced by a multitude of factors, including sedimentology, redox conditions, nutrient availability, and primary productivity.

• Leu, Marc; Schneebeli-Hermann, Elke; Hammer, Øyvind; Lindemann, Franz-Josef & Bucher, Hugo (2024). Spatiotemporal dynamics of nektonic biodiversity and vegetation shifts during the Smithian–Spathian transition: conodont and palynomorph insights from Svalbard. Lethaia: An International Journal of Palaeontology and Stratigraphy. ISSN 0024-1164. 57(2). doi: 10.18261/let.57.2.3. Full text in Research Archive Show summary

  The Smithian–Spathian transition (~249.2 Ma) is marked by profound environmental changes, carbon cycle perturbations, and the stepwise loss of nektonic biodiversity (ammonoids and conodonts). While biotic and abiotic changes have been intensely studied for the palaeosubtropics and palaeotropics, the global spatio-temporal pattern, including mid- to higher latitudes, remains unresolved. In this study, we present conodont and palynomorph data from the Lower Triassic Vikinghøgda Formation in the Stensiöfjellet section, Svalbard. Conodont samples from this sequence generally yielded relatively few specimens with one exception in the basal Vendomdalen Member, which proved exceptionally abundant and diverse. Most conodont samples of the Lusitaniadalen Member are typically dominated by middle to late Smithian segminiplanate forms, such as Scythogondolella spp. This exceptional horizon in the basal Vendomdalen Member, associated with the cosmopolitan ammonoid Bajarunia, indicates an earliest Spathian age. This sample presents the first-ever recorded conodont fauna from the earliest Spathian in the Boreal realm and associates segminiplanate with numerous segminate forms. The presence of an abundant and diverse segminate conodont fauna in northern mid-latitudes during the Early Triassic suggests that temperature was not the main regulator for their distribution, as opposed to segminiplanate forms, which were apparently more restricted to colder waters. Palynomorphs are poorly preserved but allow the discrimination of three assemblages. Association 1 is lycophyte spore dominated, and associations 2 and 3 are both dominated by bisaccate pollen. The change from lycophyte-dominated to a gymnosperm-dominated vegetation occurs just above the Wasatchites beds. A comparison with the records from the southern palaeosubtropics indicates that the vegetation shift was synchronous and coincided with the onset of a cooling episode, commencing in the latest Smithian.

• Delsett, Lene Liebe; Pyenson, Nicholas; Miedema, Feiko & Hammer, Øyvind (2023). Is the hyoid a constraint on innovation? A study in convergence driving feeding in fish-shaped marine tetrapods. Paleobiology. ISSN 0094-8373. 49(4), p. 684–699. doi: 10.1017/pab.2023.12. Full text in Research Archive Show summary

  Abstract The hyoid apparatus is essential for underwater feeding in marine tetrapods, but it is unclear whether this complex has evolved as convergently as other traits, such as dentition or locomotion. Here we compare the ossified hyoid elements in ophthalmosaurid ichthyosaurs and odontocete cetaceans, two groups with an overall similar body shape, to understand whether the hyoid elements show any signs of convergence in the context of feeding. We examined three types of data (size, morphology, and internal bone microstructure) in ophthalmosaurid and odontocete taxa in which these elements are preserved. Our data show that ichthyosaurs never experienced a shift in feeding mode, which might indicate that their hyoid apparatus never adapted to suction feeding. Also, the internal microstructure of the two animal groups differs; where the odontocetes have an overall less compact structure, ophthalmosaurid ichthyosaurs have cancellous inner cones in an outer, more compact sheath. These differences are likely explained as biomechanical adaptations to different feeding modes. Thus, the hyoid changed less and acted more as a constraint for feeding innovation in ichthyosaurs compared with cetaceans, and through a much longer time span (more than 150 Myr).

• Nielsen, Arne Thorshøj; Ahlberg, per; Ebbestad, Jan Ove R.; Hammer, Øyvind; Harper, David A.T. & Lindskog, Anders [Show all 8 contributors for this article] (2023). The Ordovician of Scandinavia: a revised regional stage classification. Geological Society Special Publication. ISSN 0305-8719. 532, p. 267–315. doi: 10.1144/SP532-2022-157. Full text in Research Archive
• Little, Crispin T.S.; Gale, Andy S; Williams, Matt; Hammer, Øyvind & Fernandez, Vincent (2023). Bivalve-barnacle pseudoplanktonic colonisation of wood from the Toarcian, Lower Jurassic, Strawberry Bank Lagerstätte, Somerset, UK. Acta Palaeontologica Polonica. ISSN 0567-7920. 68(1), p. 133–142. doi: 10.4202/app.01018.2022. Full text in Research Archive
• Engelschiøn, Victoria Sjøholt; Bernhardsen, Sofie; Wesenlund, Fredrik; Hammer, Øyvind; Hurum, Jørn Harald & Mørk, Atle (2023). Bivalve beds reveal rapid changes in ocean oxygenation in the Boreal Middle Triassic – a case study from Svalbard, Norway. Norwegian Journal of Geology. ISSN 2387-5844. 103. doi: 10.17850/njg103-2-1. Full text in Research Archive Show summary

  A fossil-rich interval in the organic-rich marine black mudstone of the Middle Triassic Botneheia Formation on eastern Svalbard was logged in high-resolution on an extremely well exposed section with emphasis on bivalve beds, taphonomic features, trace fossils and oxygenation proxies. The size distribution, fragmentation, articulation and orientation of three bivalve beds of the epifaunal flat clam Daonella were analysed. The logged section was studied for the recurrent occurrences of trace fossils and bivalve beds, and size distribution of framboidal pyrite. Daonella is most common in the shaly interval, while other taxa seem to outcompete Daonella in the siltier intervals. The comparison of fossil and sedimentological data with geochemical proxies for oxygenation revealed that the bivalve beds formed under dysoxic, conditions and due to low sedimentation rates and winnowing are not mass-mortality assemblages as previously suggested. The deposition on the sea floor was interrupted by anoxic intervals without benthic life. Recurrent beds containing the trace fossil Thalassinoides, however, show that oxygen levels fluctuated. The combination of water currents and oxygen fluctuations is a key to understanding why the black shales of the Botneheia Formation are so rich in benthic fossils

• Dupret, Vincent; Byrne, Hannah; Challands, Tom; Hammer, Øyvind; Higgs, Kenneth & Long, John [Show all 10 contributors for this article] (2023). Non-tetrapod sarcopterygians from the Valentia Slate Formation (Givetian, Devonian) of the Iveragh Peninsula, south-western Ireland: systematic reappraisal and palaeobiogeo-graphic implications. Spanish journal of palaeontology. ISSN 2255-0550. 38(1). doi: 10.7203/sjp.26527. Full text in Research Archive
• Kear, Benjamin P.; Engelschiøn, Victoria Sjøholt; Hammer, Øyvind; Roberts, Aubrey Jane & Hurum, Jørn Harald (2023). Earliest Triassic ichthyosaur fossils push back oceanic reptile origins. Current Biology. ISSN 0960-9822. 33(5), p. R178–R179. doi: 10.1016/j.cub.2022.12.053. Full text in Research Archive
• Nakrem, Hans Arne; Lindemann, Franz-Josef; Hurum, Jørn Harald & Hammer, Øyvind (2023). Fossils From the Arctic in the Collections of the Natural History Museum in Oslo, Norway. Collections: A Journal for Museum and Archives Professionals. ISSN 1550-1906. 19(3). doi: 10.1177/15501906231159039. Full text in Research Archive
• Engelschiøn, Victoria Sjøholt; Roberts, Aubrey Jane; With, Ruben & Hammer, Øyvind (2023). Exceptional X-Ray contrast: Radiography imaging of a Middle Triassic mixosaurid from Svalbard. PLOS ONE. 18(5), p. e0285939–e0285939. doi: 10.1371/journal.pone.0285939. Full text in Research Archive
• Dupret, Vincent; Byrne, Hannah M.; Castro, Nélia Sofia Cardoso; Hammer, Øyvind; Higgs, Kenneth T. & Long, Johan A. [Show all 10 contributors for this article] (2023). The Bothriolepis (Placodermi, Antiarcha) material from the Valentia Slate Formation of the Iveragh Peninsula (middle Givetian, Ireland): Morphology, evolutionary and systematic considerations, phylogenetic and palaeogeographic implications. PLOS ONE. 18(2). doi: 10.1371/journal.pone.0280208. Full text in Research Archive
• Park, Junhee; Stein, Holly Jayne; Hannah, Judith Louise; Georgiev, Svetoslav V.; Hammer, Øyvind & Olaussen, Snorre (2023). Re-Os geochronology of the Middle to Upper Jurassic marine black shales in the Agardhfjellet Formation, Central Spitsbergen, Svalbard: A cornerstone for global faunal correlation and Os isotopic change. Palaeogeography, Palaeoclimatology, Palaeoecology. ISSN 0031-0182. 633. doi: 10.1016/j.palaeo.2023.111878. Full text in Research Archive
• Collignon, Marine; Cardellini, Carlo; Duprat-Oualid, S.; Hammer, Øyvind; Chiodini, Giovanni & Vandemeulebrouck, Jean [Show all 10 contributors for this article] (2021). Carbon dioxide diffuse emission at the Tolhuaca hydrothermal system (Chile) controlled by tectonics and topography. Journal of Volcanology and Geothermal Research. ISSN 0377-0273. 417, p. 1–17. doi: 10.1016/j.jvolgeores.2021.107316. Full text in Research Archive
• Hjalmarsdottir, Hanna Rosa; Hammer, Øyvind; Nagy, Jenø & Grundvåg, Sten-Andreas (2021). Foraminiferal stratigraphy and palaeoenvironment of a storm-influenced marine shelf: upper Aptian – lower Albian, Svalbard, Arctic Norway. Cretaceous research (Print). ISSN 0195-6671. 130. doi: 10.1016/j.cretres.2021.105033. Full text in Research Archive Show summary

  This study presents the first record of foraminifera from the Lower Cretaceous Carolinefjellet Formation on the Svalbard archipelago, Arctic Norway. The Svalbard foraminiferal assemblages are dominated by agglutinated forms with a subordinate calcareous component. Several stratigraphically important species are recognised, and four assemblage zones are established: 1) Serovaina loetterlei Zone of middle Aptian or lower, 2) Ammobaculites wenonahae Zone of the middle Aptian, 3) Gaudryina tailleuri Zone of the upper Aptian, 4) Verneuilinoides borealis Zone of the lower Albian. The assemblages exhibit characteristic Boreal features, previously reported from the North Slope of Alaska, Arctic Canada, Western Siberia, and older Mesozoic strata in Svalbard. The study therefore allows for Circum-Arctic correlations and the extensions of stratigraphic ranges of several Boreal species. The investigated succession exhibits a large-scale fining-upwards trend. The lower part (the Dalkjegla Member) is characterised by abundant hummocky cross-stratified and wave-ripple cross-laminated sandstone beds, indicating deposition on a storm-dominated shelf. The upper part (the Innkjegla Member) is dominated by mudstones containing strata-bound siderite concretions and carbonate-cemented sandstone beds, suggesting deposition under more quiescent, middle to outer shelf conditions. An upwards increase in trace fossil diversity and degree of bioturbation, in concert with expanding foraminiferal diversity and morphogroup variability, reflects a long-term deepening of the shelf with fluctuating oxygen conditions. In combination with XRF data, diversity statistics, and morphogroup application, the present study thus sheds a new light on higher frequency palaeoenvironmental changes in upper part of the Carolinefjellet Formation

• Rodríguez-Tovar, F.J.; Dorador, J.; Zuchuat, Valentin; Planke, Sverre & Hammer, Øyvind (2021). Response of macrobenthic trace maker community to the end-Permian mass extinction in Central Spitsbergen, Svalbard. Palaeogeography, Palaeoclimatology, Palaeoecology. ISSN 0031-0182. 581. doi: 10.1016/j.palaeo.2021.110637. Full text in Research Archive
• Mattsson, Tobias; Petri, Benoît; Almqvist, Bjarne S.G.; McCarthy, William; Burchardt, Steffi & Palma, Octavio [Show all 8 contributors for this article] (2021). Decrypting Magnetic Fabrics (AMS, AARM, AIRM) Through the Analysis of Mineral Shape Fabrics and Distribution Anisotropy. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 126(6). doi: 10.1029/2021JB021895. Full text in Research Archive Show summary

  Anisotropy of magnetic susceptibility (AMS) and anisotropy of magnetic remanence (AARM and AIRM) are efficient and versatile techniques to indirectly determine rock fabrics. Yet, deciphering the source of a magnetic fabric remains a crucial and challenging step, notably in the presence of ferrimagnetic phases. Here we use X-ray micro-computed tomography to directly compare mineral shape-preferred orientation and spatial distribution fabrics to AMS, AARM and AIRM fabrics from five hypabyssal trachyandesite samples. Magnetite grains in the trachyandesite are euhedral with a mean aspect ratio of 1.44 (0.24 s.d., long/short axis), and >50% of the magnetite grains occur in clusters, and they are therefore prone to interact magnetically. Amphibole grains are prolate with magnetite in breakdown rims. We identified three components of the petrofabric that influence the AMS of the analyzed samples: The magnetite and the amphibole shape fabrics and the magnetite distribution anisotropy. Depending on their relative strength, orientation and shape, these three components interfere either constructively or destructively to produce the AMS fabric. If the three components are coaxial, the result is a relatively strongly anisotropic AMS fabric (P' = 1.079). If shape fabrics and/or magnetite distribution anisotropy are non-coaxial, the resulting AMS is weakly anisotropic (P' = 1.012). This study thus reports quantitative petrofabric data that show the effect of magnetite distribution anisotropy on magnetic fabrics in igneous rocks, which has so far only been predicted by experimental and theoretical models. Our results have first-order implications for the interpretation of petrofabrics using magnetic methods.

• Mason, Matthew J.; Wenger, Lea M.D.; Hammer, Øyvind & Blix, Arnoldus S (2020). Structure and function of respiratory turbinates in phocid seals. Polar Biology. ISSN 0722-4060. 43(2), p. 157–173. doi: 10.1007/s00300-019-02618-w. Full text in Research Archive Show summary

  In terrestrial mammals, the respiratory turbinate bones within the nasal cavity are employed to conserve heat and water. In order to investigate whether environmental temperature affects respiratory turbinate structure in phocids, we used micro-computed tomography to compare maxilloturbinate bone morphology in polar seals, grey seals and monk seals. The maxilloturbinates of polar seals have much higher surface areas than those of monk seals, the result of the polar seals having more densely packed, complex turbinates within larger nasal cavities. Grey seals were intermediate; a juvenile of this species proved to have more densely packed maxilloturbinates with shorter branch lengths than a conspecific adult. Fractal dimension in the densest part of the maxilloturbinate mass was very close to 2 in all seals, indicating that these convoluted bones evenly fill the available space. The much more elaborate maxilloturbinate systems in polar seals, compared with monk seals, are consistent with a greater need to limit respiratory heat loss.

• Zuchuat, Valentin; Sleveland, Arve; Twitchett, Richard; Svensen, Henrik; Turner, Holly & Augland, Lars Eivind [Show all 12 contributors for this article] (2020). A new high-resolution stratigraphic and palaeoenvironmental record spanning the End-Permian Mass Extinction and its aftermath in central Spitsbergen, Svalbard. Palaeogeography, Palaeoclimatology, Palaeoecology. ISSN 0031-0182. 554. doi: 10.1016/j.palaeo.2020.109732. Full text in Research Archive Show summary

  Research on the Permian-Triassic boundary (PTB) along the northern margins of Pangaea (exposed today in the Arctic region) has been heavily reliant on field observations, where data resolution was consequently determined by outcrop condition and accessibility. Core drilling in central Spitsbergen allowed for a near-complete recovery of two ~90 m cores through the PTB. Analyses of the core and nearby outcrops include stratigraphic logging and sampling, XRF scanning, petrography, biostratigraphy, isotope geochemistry, and geochronology. The First Appearance Datum (FAD) of H. parvus in Svalbard places the base of the Triassic ca. 4 m above the base of the Vikinghøgda Formation, and ca. 2.50 m above the End-Permian Mass Extinction (EPME) and its associated sharp negative δ13C. The PTB therefore falls within the Reduviasporonites chalastus Assemblage Zone in Svalbard. Precise U-Pb TIMS dating of two zircon crystals in a tephra layer just above the first documented Hindeodus parvus in Svalbard gives an age of 252.13 ± 0.62 Ma. High-resolution palaeoenvironmental proxies, including Si/kcps (kilo counts per second), Zr/Rb, K/Ti, Fe/K, and V/Cr, indicate a transition towards a more arid climate in the earliest Triassic, contemporaneous with prolonged bottom-water dysoxic/anoxic conditions, following an increase in volcanic activity in the Late Permian. Statistical analysis of Zr/Rb, K/Ti and V/Cr elemental ratios suggests that the system was impacted by long-eccentricity (400 kyr) cyclicity. The δ13C excursion in organic carbon (δ13Corg) record signals a large negative carbon isotope excursion (CIE) associated with the mass extinction event, but also records a second, smaller negative CIE ca. 22 m above this interval. This younger δ13Corg excursion correlates to similar CIEs in the Dienerian (late Induan) records of other sections, notably in the Tethys Ocean, which have been interpreted as recording a small biotic crisis during the post-extinction recovery. Evidence of this negative CIE in Spitsbergen suggests that the Dienerian crisis may have been global in extent. The negative δ13Corg values are associated with evidence for dysoxia or anoxia in the core, and the occurrence of tephra layers in the same interval suggests a possible connection between the Dienerian crisis and a discrete episode of volcanic activity.

• Hansen, Bitten Bolvig; Bucher, Hugo; Schneebeli-Hermann, Elke & Hammer, Øyvind (2020). The middle Smithian (Early Triassic) ammonoid Arctoceras blomstrandi: conch morphology and ornamentation in relation to stratigraphy. Papers in Palaeontology. ISSN 2056-2799. doi: 10.1002/spp2.1348. Full text in Research Archive
• Svensen, Henrik; Hammer, Øyvind; Chevallier, Luc; Jerram, Dougal Alexander; Silkoset, Petter & Polteau, Stephane [Show all 7 contributors for this article] (2020). Understanding thermogenic degassing in large igneous provinces: Inferences from the geological and statistical characteristics of breccia pipes in the western parts of the Karoo Basin. In Adatte, Thierry; Bond, David P.G. & Keller, Gerta (Ed.), Mass extinctions, volcanism, and impacts. The Geological Society of America. ISSN 9780813725444. p. 67–84. Full text in Research Archive
• Hammer, Øyvind; Alsen, Peter; Grundvåg, Sten-Andreas; Jelby, Mads E.; Nøhr-Hansen, Henrik & Olaussen, Snorre [Show all 9 contributors for this article] (2019). Comment on ‘Redox conditions, productivity, and volcanic inputduring deposition of uppermost Jurassic and Lower Cretaceousorganic-rich siltstones in Spitsbergen, Norway’ by Rakocinski et al.(2018). Cretaceous research (Print). ISSN 0195-6671. 96, p. 241–243. doi: 10.1016/j.cretres.2018.09.017. Full text in Research Archive
• Hammer, Øyvind; Jones, Morgan Thomas; Schneebeli-Hermann, Elke; Hansen, Bitten Bolvig & Bucher, Hugo (2019). Are Early Triassic extinction events associated with mercury anomalies? A reassessment of the Smithian/Spathian boundary extinction. Earth-Science Reviews. ISSN 0012-8252. 195, p. 179–190. doi: 10.1016/j.earscirev.2019.04.016. Full text in Research Archive Show summary

  High concentrations of mercury, possibly connected with widespread volcanism of the Siberian Traps, have previously been associated with the Smithian/Spathian (Early Triassic) boundary (SSB) in the Sverdrup Basin, Tethyan sections in India and China, as well as with a shallow-water record in western Spitsbergen. We confirm this Hg/TOC anomaly in the deeper water record at Wallenbergfjellet, central Spitsbergen. However, both paleontological age control and carbon isotopes indicate that the Hg anomaly occurred mainly within strata of middle Smithian age. Therefore, this Hg anomaly is unlikely to be directly and causally related to mechanisms contributing to the late Smithian global extinction of nektonic faunas. The TOC and trace element data suggest generally more oxygenated conditions during the Smithian compared to the Spathian, which is at odds with the hypothesis that oxygen depletion may have been a global kill mechanism for the SSB extinction. Further work is needed to assess if precise timing and paleogeographic distribution of anoxia shows any consistent pattern or not during the Smithian and Spathian. The very abrupt lower limb of the positive carbon isotope excursion (CIE) and the coarser grain size immediately below the boundary between the Lusitaniadalen Member and the Vendomdalen Member indicate a substantial stratigraphic gap of latest Smithian age, a previously neglected signal shared with many other boreal SSB sections. Ammonoid age control also indicates that the onset of the late Smithian gap in the high latitudes was earlier than in the Tropics. The gradual end of the positive CIE contrasts with the frequent spike shape observed in tropical shelf records and is definitively earliest Spathian in age. The middle Smithian Hg anomaly in the Boreal record is only visible in the Hg/TOC values, and is associated with a possible shift in organic matter type from terrestrial to marine in the case of Spitsbergen. This suggests that the middle Smithian Hg/TOC anomaly in Spitsbergen may not unequivocally originate from volcanism, and calls for additional caution before interpreting Hg spikes as a volcanic proxy.

• Delsett, Lene Liebe; Druckenmiller, Patrick Scott; Hammer, Øyvind; Hryniewicz, Krzysztof; Knutsen, Espen Madsen & Koevoets, Maayke Jacqueline [Show all 9 contributors for this article] (2019). Mesozoic marine reptiles from Spitsbergen and their ecosystems. Geology Today. ISSN 0266-6979. 35(1), p. 20–25. doi: 10.1111/gto.12256. Full text in Research Archive Show summary

  In the Mesozoic seas, the apex predators were reptiles. From the Arctic archipelago of Svalbard, the Spitsbergen Mesozoic Research Group has excavated numerous well preserved marine reptile skeletons in order to understand the biology of these animals and the environment they lived in. The work of eleven field seasons has made this one of the largest and most productive palaeontological research projects in the high Arctic world‐wide. The initial eight seasons focused on one of the richest occurrences of Late Jurassic—earliest Cretaceous (c. 150–139 Ma) marine reptiles in the world, and nearly sixty specimens have been collected, together with a diverse assemblage of invertebrates, some of which are associated with methane seeps. The last three seasons were spent investigating events further back in time, as Spitsbergen preserves the remains from some of the first marine reptile radiations in the wake of the most devastating extinction in the history of the Earth, at the Permian–Triassic boundary (c. 252 Ma).

• Burchardt, Steffi; Mattsson, Tobias; Palma, J Octavio; Galland, Olivier; Almqvist, Bjarne & Mair, Karen [Show all 9 contributors for this article] (2019). Progressive Growth of the Cerro Bayo Cryptodome, Chachahuen Volcano, Argentina?Implications for Viscous Magma Emplacement. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 124(8), p. 7934–7961. doi: 10.1029/2019JB017543. Full text in Research Archive
• Sucheras-Marx, Baptiste; Escarguel, Gilles; Ferreira, J & Hammer, Øyvind (2019). Statistical confidence intervals for relative abundances and abundance-based ratios: Simple practical solutions for an old overlooked question. Marine Micropaleontology. ISSN 0377-8398. 151. doi: 10.1016/j.marmicro.2019.101751. Full text in Research Archive
• Markussen, Ørjan; Dypvik, Henning; Hammer, Erik; Long-Sanouiller, Haili & Hammer, Øyvind (2019). 3D characterization of porosity and authigenic cementation in Triassic conglomerates/arenites in the Edvard Grieg Field using 3D micro-CT imaging. Marine and Petroleum Geology. ISSN 0264-8172. 99, p. 265–281. doi: 10.1016/j.marpetgeo.2018.10.015. Full text in Research Archive
• Koevoets, Maayke Jacqueline; Hammer, Øyvind & Little, Crispin T.S. (2019). Palaeoecology and palaeoenvironments of the Middle Jurassic to lowermost Cretaceous Agardhfjellet Formation (Bathonian–Ryazanian), Spitsbergen, Svalbard. Norwegian Journal of Geology. ISSN 2387-5844. 99(1), p. 17–40. doi: 10.17850/njg99-1-02. Full text in Research Archive
• Bjørklund, Kjell Rasmus; Kruglikova, Svetlana B. & Hammer, Øyvind (2019). The radiolarian fauna during the younger dryas–holocene transition in andfjorden, northern Norway. Polar Research. ISSN 0800-0395. 38. doi: 10.33265/polar.v38.3444. Full text in Research Archive
• Ballo, Eirik Magnus Gottschalk; Augland, Lars Eivind; Hammer, Øyvind & Svensen, Henrik (2019). A new age model for the Ordovician (Sandbian) K-bentonites in Oslo, Norway. Palaeogeography, Palaeoclimatology, Palaeoecology. ISSN 0031-0182. 520, p. 203–213. doi: 10.1016/j.palaeo.2019.01.016. Full text in Research Archive Show summary

  During the Late Ordovician, large explosive volcanic eruptions deposited worldwide K-bentonites, including the Millbrig and Deicke K-bentonites in North America and the Kinnekulle K-bentonite in Scandinavia. We have studied a classical locality in Oslo containing one of the most complete sections of K-bentonites in Europe. In a 53 m section of Sandbian age, we discovered 33 individual K-bentonite beds, the most notable beds being the Kinnekulle and the upper Grimstorp K-bentonite. Magnetic susceptibility (MS) measurements on two intervals show significant periodicity peaks interpreted as Milankovitch cycles and thus astronomically forced changes in sediment supply and composition. These cycles fit remarkably well with both the expected Milankovitch periodicities for the Ordovician as well as the radiometric ages presented in this study and may represent one of the most convincing demonstrations of Milankovitch cycles from the lower Paleozoic so far. Five of the K-bentonites have been dated by high-precision chemical abrasion-thermal ionization mass spectrometry (CA-TIMS) U-Pb zircon geochronology, where the Kinnekulle K-bentonite gives an age of 454.06 ± 0.43 Ma. We have integrated the new data and calculated an age model showing the sedimentation rates through the section and thereby the ages of each of the 33 K-bentonites. Using the age model, we further present a new age for the Sandbian-Katian stage boundary. The section in Oslo provides the highest resolution window into the Upper Ordovician K-bentonite succession so far and helps shed more light on the chronology of one of the most intense volcanic periods of the Paleozoic and the relationship with the global carbon cycle changes that followed.

• Koevoets, Maayke Jacqueline; Hurum, Jørn Harald & Hammer, Øyvind (2018). New late jurassic teleost remains from the agardhfjellet formation, Spitsbergen, Svalbard. Norwegian Journal of Geology. ISSN 2387-5844. 98(2), p. 289–299. doi: 10.17850/njg98-2-01. Full text in Research Archive Show summary

  The Agardhfjellet Formation (Middle Jurassic to lowermost Cretaceous) of Svalbard (Norwegian Arctic) is well known for its abundant and unique marine reptile fauna, of ichthyosaurs and plesiosaurs. In an attempt to reconstruct the palaeoecology and palaeoenvironment of the Agardhfjellet Formation, a study of the invertebrate fauna, geochemistry and stratigraphy was conducted. During this study numerous small vertebrate fossils were encountered. Only a few reports of Jurassic teleost from the Arctic were known previously, from the Agardhfjellet Formation on Svenskoya, Kong Karls Land, described as Leptolepis nathorsti, and at Lardyfjellet, East Spitsbergen. We describe more teleost material from the Kimmeridgian and Volgian of the Agardhfjellet Formation in central Spitsbergen and assign a new age, Kimmeridgian, to the original material. This new material also provides more information on the palaeoecology of the Jurassic of Svalbard, showing that fish were probably common in the pelagic fauna of central Spitsbergen together with the better known cephalopods, and could have been important elements of the diet of the marine reptiles.

• Hurum, Jørn Harald; Engelschiøn, Victoria Sjøholt; Økland, Inghild Halvorsen; Bratvold, Janne; Ekeheien, Christina Pokrie & Roberts, Aubrey Jane [Show all 12 contributors for this article] (2018). The history of exploration and stratigraphy of the Early to Middle Triassic vertebrate-bearing strata of Svalbard (Sassendalen Group, Spitsbergen). Norwegian Journal of Geology. ISSN 2387-5844. 98(2), p. 165–174. doi: 10.17850/njg98-2-04. Full text in Research Archive Show summary

  The palaeontology of the Lower to Middle Triassic succession in Spitsbergen has been studied for more than a century and a half. Our ability to properly interpret the evolutionary and ecological implications of the faunas requires precise stratigraphic control that has only recently become available. Within such a detailed stratigraphic framework, the Spitsbergen fossil material promises to contribute to our understanding of the faunal recovery after the end-Permian mass extinction.

• Koevoets, Maayke Jacqueline; Hammer, Øyvind; Olaussen, Snorre; Senger, Kim & Smelror, Morten (2018). Integrating subsurface and outcrop data of the Middle Jurassic to Lower Cretaceous Agardhfjellet Formation in central Spitsbergen. Norwegian Journal of Geology. ISSN 2387-5844. 98(4). doi: 10.17850/njg98-4-01. Full text in Research Archive Show summary

  The Longyearbyen CO2 storage project drilling and coring campaign in central Spitsbergen provided new insights on the shale-dominated Middle Jurassic to Lower Cretaceous Agardhfjellet Formation, which is the onshore counterpart to the Fuglen Formation and the prolific source rocks of the Hekkingen Formation in the Barents Sea. Logs of magnetic susceptibility, organic carbon content, organic carbon isotopes and XRF geochemistry on the cores, together with wireline logs, biostratigraphy and sedimentology, have made it possible to refine the interpretation of the depositional environment and to identify transgressive-regressive (TR) sequences. Several key sequence-stratigraphic surfaces are identified and suggested to be correlative in Central Svalbard, and four of them, although not necessarily chronostratigraphic, also to surfaces in the Barents Sea. Due to the nearly flat-lying thrust faults in the upper décollement zone of the West Spitsbergen Fold and Thrust Belt, there is some concern about the lateral correlation of the sequences within Spitsbergen. However, some of the TR sequence surfaces appear to be of regional importance and are recognised both onshore Svalbard and offshore on the Barents Shelf. The observations suggest a shallow-marine shelf depositional environment within an epicontinental sea with variable dysoxic, anoxic and oxic sea-floor conditions. The majority of the facies vary from outer shelf to transition zone or prodelta and lower shoreface/distal delta front. In one outcrop, proximal facies, i.e., delta front or middle shoreface, are recognised. In our study area the nearly 250 m-thick, fine-grained Agardhfjellet Formation is proposed to represent distal shoreline clinoforms and a precursor to the overlying forward- and southward-stepping wedge of the Valanginian Rurikfjellet Formation and the Barremian to Early Aptian Helvetiafjellet Formation.

• Hansen, Bitten Bolvig; Hammer, Øyvind & Nakrem, Hans Arne (2018). Stratigraphy and age of the Grippia niveau bonebed, Lower Triassic Vikinghøgda Formation, Spitsbergen. Norwegian Journal of Geology. ISSN 2387-5844. 98(2), p. 175–187. doi: 10.17850/njg98-2-02. Full text in Research Archive Show summary

  We report on a newly excavated Spathian (Lower Triassic) bonebed on Marmierfjellet, Central Spitsbergen. The bonebed contains a varied material of bones and teeth from marine vertebrates along with conodont elements. The fauna of the bonebed could prove interesting in a global context of recovery and speciation after the Late Permian mass extinction. For this reason it is important to place the bonebed in a stratigraphic and chronologic framework. The bonebed sits within the Grippia niveau and is likely to be the one first described by Stensiö in 1921. The bonebed and the Grippia niveau are part of the Vendomdalen Member of the Vikinghøgda Formation. Based on the level in the stratigraphy, the bonebed most likely correlates to the Bajarunia euomphala Zone or the Parasibirites grambergi Zone which makes it either early or early/middle Spathian in age. Some conodont elements from the bonebed are reworked from older sediments but the youngest found are supporting a Spathian age. Vanadium data and TOC content from the bonebed indicate that it was formed under increasingly anoxic conditions.

• Tasianas, Alexandros; Bünz, Stefan; Bellwald, Benjamin; Hammer, Øyvind; Planke, Sverre & Lebedeva-Ivanova, Nina [Show all 7 contributors for this article] (2018). High-resolution 3D seismic study of pockmarks and shallow fluid flow systems at the Snøhvit hydrocarbon field in the SW Barents Sea. Marine Geology. ISSN 0025-3227. 403, p. 247–261. doi: 10.1016/j.margeo.2018.06.012. Full text in Research Archive Show summary

  The Barents Sea is an epicontinental shelf sea with a fragmented structure consisting of long fault complexes, basins and basement highs. Fluid leakage from deep-seated hydrocarbon accumulations is a widespread phenomenon and mostly related to its denudation history during the glacial/interglacial cycles. In this study, we aimed to better understand shallow fluid flow processes that have led to the formation of numerous pockmarks observed at the seabed, in this area. To achieve this goal, we acquired and interpreted high-resolution 3D seismic and multibeam swath bathymetry data from the Snøhvit area in the Hammerfest Basin, SW Barents Sea. The high-resolution 3D seismic data were obtained using the P-Cable system, which consists of 14 streamers and allows for a vertical resolution of ~1.5 m and a bin size of 6.25 × 6.25 m to be obtained. The frequency bandwidth of this type of acquisition configuration is approximately 50–300 Hz. Seismic surfaces and volume attributes, such as variance and amplitude, have been used to identify potential fluid accumulations and fluid flow pathways. Several small fluid accumulations occur at the Upper Regional Unconformity separating the glacial and pre-glacial sedimentary formations. Together, these subsurface structures and fluid accumulations control the presence of pockmarks in the Snøhvit study area. Two different types of pockmarks occur at the seabed: a few pockmarks with elliptical shape, up to a few hundred meters wide and with depths up to 12 m, and numerous circular, small, “unit pockmarks” that are only up to 20 m wide and up to 1 m deep. Both types of pockmarks are found within glacial ploughmarks, suggesting that they likely formed during deglaciation or afterwards. Some of the larger normal pockmarks show columnar leakage zones beneath them. Pressure and temperature conditions were favourable for the formation of gas hydrates. During deglaciation, gases may have been released from dissociating gas hydrates prolonging the period over which active seepage occurred. At present, there is no evidence from the 3D seismic data of active gas seepage in the Snøhvit area. Low sedimentation rates or the influence of strong deep ocean currents may explain why these pockmarks can still be identified on the contemporary seabed.

• Gyøry, Emil; Hammer, Øyvind; Jorde, Knut; Nakrem, Hans Arne; Swajda, Michaël & Domeier, Mathew (2018). The origin of telemarkites from the mesoproterozoic of telemark, Norway. Norwegian Journal of Geology. ISSN 2387-5844. 98(1), p. 25–39. doi: 10.17850/njg98-1-03. Full text in Research Archive Show summary

  The possible macrofossil Telemarkites enigmaticus from the Mesoproterozoic Gjuve Formation, Telemark supracrustals, southern Norway, was described by Dons in 1959. We here present finds of similar, but larger structures from the somewhat older Åmot Formation (c. 1150–1250 Ma). The elongated, strongly oriented, nodular structures are up to 25 cm long with a carbonate-rich core, and occur in metasandstones of probable lacustrine origin. The structures and surrounding rocks have been studied with a number of techniques, including XRD, XRF, petrographic thinsections, SEM-EDS, X-ray and CT imaging, hyperspectral imaging, anisotropy of magnetic susceptibility, stable isotope analysis (δ13C and δ18O) and palynological preparation. Convoluted and domed beds could represent metamorphosed microbialites, deriving from algal or bacterial mats. The nodular structures remain enigmatic, but may represent oncoids, desiccation features (rollup structures), early diagenetic concretions shaped by groundwater flow, or macrofossils of unknown biological affinity. The structure Telemarkites giganticus Gyøry, Hammer, Jorde, Nakrem, Swajda & Domeier sp. nov. is formally described.

• Hammer, Øyvind & Svensen, Henrik (2017). Biostratigraphy and carbon and nitrogen geochemistry of the SPICE event in Cambrian low-grade metamorphic black shale, Southern Norway. Palaeogeography, Palaeoclimatology, Palaeoecology. ISSN 0031-0182. 468, p. 216–227. doi: 10.1016/j.palaeo.2016.12.016. Full text in Research Archive
• Mazzini, Adriano; Svensen, Henrik; Forsberg, Carl Fredrik; Linge, Henriette; Lauritzen, Stein-Erik & Haflidason, Haflidi [Show all 9 contributors for this article] (2017). A climatic trigger for the giant Troll pockmark field in the northern North Sea. Earth and Planetary Science Letters. ISSN 0012-821X. 464, p. 24–34. doi: 10.1016/j.epsl.2017.02.014. Full text in Research Archive Show summary

  Pockmarks are seafloor craters usually formed during methane release on continental margins. However, the mechanisms behind their formation and dynamics remain elusive. Here we report detailed investigations on one of the World's largest pockmark fields located in the Troll region in the northern North Sea. Seafloor investigations show that >7000 pockmarks are present in a ∼600 km2 area. A similar density of pockmarks is likely present over a 15,000 km2 region outside our study area. Based on extensive monitoring, coring, geophysical and geochemical analyses, no indications of active gas seepage were found. Still, geochemical data from carbonate blocks collected from these pockmarks indicate a methanogenic origin linked to gas hydrate dissociation and past fluid venting at the seafloor. We have dated the carbonates using the U–Th method in order to constrain the pockmark formation. The carbonates gave an isochron age of 9.59±1.38 ka9.59±1.38 ka, i.e. belonging to the initial Holocene. Moreover, radiocarbon dating of microfossils in the sediments inside the pockmarks is consistent with the ages derived from the carbonates. Based on pressure and temperature modelling, we show that the last deglaciation could have triggered dissociation of gas hydrates present in the region of the northern part of the Norwegian Channel, causing degassing of 0.26 MtCH4/km2 at the seafloor. Our results stress the importance of external climatic forcing of the dynamics of the seafloor, and the role of the rapid warming following the Younger Dryas in pacing the marine gas hydrate reservoir.

• Neumann, Else Ragnhild; Svensen, Henrik; Polozov, Alexander & Hammer, Øyvind (2017). Formation of Si-Al-Mg-Ca-rich zoned magnetite in an end-Permian phreatomagmatic pipe in the Tunguska Basin, East Siberia. Mineralium Deposita. ISSN 0026-4598. Published ahead of print. doi: 10.1007/s00126-017-0717-9. Full text in Research Archive
• Piazza, Veronica; Hammer, Øyvind & Jattiot, Romain (2017). New late Smithian (early triassic) ammonoids from the Lusitaniadalen member, Vikingh?gda formation, Svalbard. Norsk Geologisk Tidsskrift. ISSN 0029-196X. 97(2), p. 105–117. doi: 10.17850/njg97-2-03. Full text in Research Archive
• Gradstein, Felix M; Waters, Colin N.; Charnock, Mike; Munsterman, Dirk; Hollerbach, Michelle & Brunstad, Harald [Show all 8 contributors for this article] (2016). Stratigraphic guide to the cromer knoll, shetland and chalk groups, north sea and norwegian sea. Newsletters on stratigraphy. ISSN 0078-0421. 49(1), p. 73–280. doi: 10.1127/nos/2016/0071. Full text in Research Archive
• Amberg, Chloe E.A.; Collart, Tim; Salenbien, Wout; Egger, Lisa M.; Munnecke, Axel & Nielsen, Arne T. [Show all 9 contributors for this article] (2016). The nature of Ordovician limestone-marl alternations in the Oslo-Asker District (Norway): Witnesses of primary glacio-eustasy or diagenetic rhythms? Scientific Reports. 6. doi: 10.1038/srep18787. Full text in Research Archive
• Koevoets, Maayke Jacqueline; Abay, Tesfamariam Berhane; Hammer, Øyvind & Olaussen, Snorre (2016). High-resolution organic carbon–isotope stratigraphy of the Middle Jurassic–Lower Cretaceous Agardhfjellet Formation of central Spitsbergen, Svalbard. Palaeogeography, Palaeoclimatology, Palaeoecology. ISSN 0031-0182. 449, p. 266–274. doi: 10.1016/j.palaeo.2016.02.029. Full text in Research Archive
• Hammer, Øyvind; Planke, Sverre; Hafeez, Amer; Hjelstuen, Berit Oline Blihovde; Faleide, Jan Inge & Kvalø, Frode (2016). Agderia – A postglacial lost land in the southern Norwegian North Sea. Norsk Geologisk Tidsskrift. ISSN 0029-196X. 96(1), p. 43–60. doi: 10.17850/njg96-1-05. Full text in Research Archive
• Pau, Mauro & Hammer, Øyvind (2016). Sedimentary environments in the south-western Barents sea during the last deglaciation and the Holocene : a case study outside the Ingøydjupet trough. Polar Research. ISSN 0800-0395. 35(23104). doi: 10.3402/polar.v35.23104. Full text in Research Archive
• Sigurdsen, Are & Hammer, Øyvind (2016). Body size trends in the Ordovician to earliest Silurian of the Oslo Region. Palaeogeography, Palaeoclimatology, Palaeoecology. ISSN 0031-0182. 443, p. 49–56. doi: 10.1016/j.palaeo.2015.11.038. Full text in Research Archive

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• Hammer, Øyvind & Harper, David A.T. (2024). Paleontological Data Analysis, 2nd edition. John Wiley & Sons. ISBN 9781119933953. 400 p. Full text in Research Archive
• Hammer, Øyvind & Jørgensen, Marte Holten (2020). Flora Norvegica Radiographica - Norske planter i røntgen. Spartacus. ISBN 9788243012707. 274 p. Full text in Research Archive

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• Tonti-Filippini, Justin Antony Dean; Jakobsen, R.; Hammer, Øyvind & Piispa, E. (2026). Atmospheric pressure recorded by mid-Miocene basalts in eastern Iceland. Full text in Research Archive
• Roberts, Aubrey Jane; Erlien, Wenche; Sørborg, Øystein; Hammer, Øyvind & Hurum, Jørn (2025). Bringing paleontology into the classroom: a digital teaching unit on evolution using ongoing research. Full text in Research Archive
• Hurum, Jørn; Roberts, Aubrey Jane; Hammer, Øyvind; Sørborg, Øystein & Erlien, Wenche (2025). Fossils and evolution - the viten.no program. doi: https:/www.viten.no/filarkiv/evolution/#%2F. Full text in Research Archive
• Hurum, Jørn; Hammer, Øyvind; Roberts, Aubrey Jane & Rucinski, Maciej Roman (2025). Dinosaurene lever! doi: https:/www.verdenskulestedag.no/. Full text in Research Archive
• Hurum, Jørn Harald; Roberts, Aubrey Jane; Hammer, Øyvind; Erlien, Wenche & Sørborg, Øystein (2025). fossiler og evolusjon. doi: https:/www.viten.no/filarkiv/evolusjon/#%2F. Full text in Research Archive
• Zimmerman, Aaron; Reynard, Bruno; Kreiner, Douglas C; Stein, Holly; Hannah, Judith & Kimball, Justin [Show all 8 contributors for this article] (2025). Re-Os Lens on the Enigmatic Pogo Au District, Tintina Au Province, Alaska. Goldschmidt Conference Abstracts. 2025. Full text in Research Archive Show summary

  Models for low-sulfide, quartz vein hosted Au deposits are many and highly variable, whether the discussion be on relationship to magma composition, fluid source, or Au source(s) and transport. The well-endowed Tintina Au Province, spanning interior Alaska and the Yukon is exemplary, containing numerous diverse gold deposits that prove difficult to relate to one another. Pogo lacks obvious temporally related intrusion(s) for a potential Au source, even as the metamorphosed (pre-120 Ma) Devonian-Mississippian basement is filled with Cretaceous intrusions emplaced continuously from ~115-90 Ma across the region. Pogo is defined by gently northwest-dipping sheeted quartz-dominant lodes exhibiting variable pre- and post-mineralization fault-related deformation. Gold-bearing quartz lodes exhibit overprinting relations including quartz textures that present as multiple ghost breccias with multiple annealing events. Magmatism in the immediate region is restricted to ~114-112 Ma altered and mineralized peraluminous granites, the ~107 Ma Goodpaster batholith >5 km away, and ~98-93 Ma monzodiorite plutons cutting mineralization. Re-Os geochronology on Au-associated sulfides (pyrrhotite and arsenopyrite) in some Pogo deposits suggest pyrrhotite may be slightly older (~112-110 Ma). The majority of arsenopyrite (interestingly, two varieties, one with and the other without common Os) provides Re-Os ages of ~106-105 Ma. Here we address an unexpected age of ~142 Ma, determined for a highly unusual vein type at Pogo. Non-planar, hairline to 3-mm auriferous sulfide veinlets with tight squiggle-like morphologies, prominently crisscross an undefined, but seemingly early quartz generation. The mineralogy of these veins is pyrrhotite and arsenopyrite, with disseminated Au, and Bi2Te3. Both SEM and CT imaging support emplacement of the auriferous sulfide veinlets during a catastrophic event that appears to have produced nearly simultaneous sulfide-Au-Bi-Te and local quartz melt. Rounded sulfide-Au- Bi2Te3 melt-like blobs are suspended in quartz together with mostly rounded quartz grains containing the same sulfide-Au-Bi-Te mineralogy as the vein. Melting, freezing and brecciation may define a nearly instantaneous geologic time span. Significantly, initial 187Os/188Os ratios for key isochrons are chondritic. We are presently investigating quartz and Pogo’s non-magnetic pyrrhotite using Raman spectroscopy, in the context of a possible impact origin for early Pogo mineralization. Special thanks to Northern Star for samples and support.

• Nakrem, Hans Arne; Hurum, Jørn Harald & Hammer, Øyvind (2025). From dinoflagellates to dinosaurs ‐ 20 years with the Spitsbergen Mesozoic Research Group (SMRG). NGF Abstracts and Proceedings of the Geological Society of Norway. 2025(01), p. 70–71. doi: https:/geologi.no/konferanser/vinterkonferanser/abstracts/file/298-abst-vk25. Full text in Research Archive Show summary

  In 2001 a group of students and a teacher from the University Studies at Svalbard (UNIS) stumbled upon a partial skeleton of a plesiosaur at Janusfjellet, inner Isfjorden, Spitsbergen. This find sparked extensive fieldwork by SMRG over the next 20 years. Several expeditions were also undertaken in cooperation with other research groups.

• Hammer, Øyvind & Hurum, Jørn Harald (2024). Modeller i et geologisk museum. Naturfag. ISSN 1504-4564. p. 68–73. Full text in Research Archive
• Hurum, Jørn Harald; Nakrem, Hans Arne; Hammer, Øyvind; Roberts, Aubrey Jane; Delsett, Lene Liebe & Engelschiøn, Victoria Sjøholt (2024). 20 years of Arctic excavations and research – Spitsbergen Mesozoic Research Group (SMRG). Full text in Research Archive
• Hammer, Øyvind (2024). Hvorfor var dyrene rarere før? Og hvorfor var de så store? Paleobloggen. Full text in Research Archive
• Hammer, Øyvind (2024). Hvorfor paleontologi? Paleobloggen. Full text in Research Archive
• Jones, Morgan; Rooney, Alan; Zuchuat, Valentin; Turner, Holly; Frieling, Joost & Mather, Tamsin [Show all 14 contributors for this article] (2024). Volcanic proxies from the northern Pangean margin across the Permian-Triassic boundary: Evidence of intermittent Siberian Traps activity. Full text in Research Archive
• Nordenhaug, Petter; Engelschiøn, Victoria Sjøholt; Roberts, Aubrey Jane; With, Ruben & Hammer, Øyvind (2024). Deeply rooted — a study of heterodontid mixosaurids from Svalbard using radiography. Full text in Research Archive
• Hammer, Øyvind (2023). Levende begravet – en skrekkhistorie fra middelalderen. Paleobloggen. Full text in Research Archive
• Hammer, Øyvind (2023). En flyndre fra Økern. Paleobloggen. Full text in Research Archive
• Hurum, Jørn Harald; Hammer, Øyvind; Friis, Henrik; Müller, Axel; Engelschiøn, Victoria Sjøholt & Strøm, Marianne (2023). En kort veiledning for de nye utstillingene i Geologisk hus, Naturhistorisk museum, Universitetet i Oslo. Stein. ISSN 0802-9121. p. 3–13. Full text in Research Archive
• Amundsen, Madelen; Hammer, Øyvind & Nakrem, Hans Arne (2023). Massedød hos trilobitter, ordovicium, Marokko. Stein. ISSN 0802-9121. 2023(4), p. 18–22. Full text in Research Archive
• Delsett, Lene Liebe; Pyenson, Nicholas; Miedema, Feiko & Hammer, Øyvind (2022). The hyoid arch and feeding in two fish-shaped marine tetrapods. Full text in Research Archive
• Zuchuat, Valentin; Augland, Lars Eivind; Jones, Morgan Thomas; Sleveland, Arve R.N.; Twitchett, Richard & Tovar, Francisco J Rodríguez [Show all 13 contributors for this article] (2022). The Permian-Triassic boundary across the Barents Shelf: an intricate record of climate change, mass extinction, recovery, and basin reorganisation. EGU General Assembly. doi: 10.5194/egusphere-egu22-2379. Full text in Research Archive
• Park, Juni; Stein, Holly J.; Hannah, Judith L.; Georgiev, Svetoslav; Yang, Gang & Hammer, Øyvind [Show all 7 contributors for this article] (2021). Re-Os geochronology of black shale from Central Spitsbergen, Svalbard: a stepping stone toward establishing the age of the J/K boundary. Full text in Research Archive Show summary

  Stage boundaries are determined by integrating bio-, magneto-, and chrono-stratigraphic units. Numerical ages of stage boundaries ideally should be constrained or verified by reliable radiometric ages of sedimentary strata – a challenging task in the absence of ash layers suitable for U-Pb zircon dating. For example, the numerical age of the Jurassic – Cretaceous (J/K) boundary is still uncertain. Recent efforts provided some ammonite biostratigraphy across the J/K boundary in the Slottsmøya Member of the Agardhfjellet Formation on Spitsbergen. However, the age and duration of the uppermost Jurassic (Volgiann stage) and the lowermost Cretaceous (Ryazanian stage) in the Boreal realm remain loosely defined. Our study adds new radiometric ages for this controversial stage boundary and presents geochemical data to evaluate paleoenvironmental settings. Three black shale intervals from two drill cores (DH2 and DH5) located ~7 km apart in Central Spitsbergen provide three Re-Os ages. In DH2, shales from the Slottsmøya Member previously provided conflicting biostratigraphic results (Volgian toRyazanian)[1]. An isochron derived from samples at 497m depth yields an imprecise 146.8 ± 6.8 Ma age, suggesting deposition in the Upper Volgian rather th precludes confirmation. Large uncertainties near the J/K boundary are typical for this region[2, 3]. Two Re-Os isochron ages from the Oppdalen Member (DH2 at 724 and DH5 at 658 m) yield similar ages of 157.6 ± 3.3 Ma and 157.9 ± 2.9 Ma, respectively. These ages are close to the GTS Oxfordian – Kimmeridgian stage boundary and, even within their uncertainties, suggest Oxfordian – Kimmeridgian deposition. The agreement between these correlative intervals in the two cores[4] lends credence to the accuracy of the Re-Os age. Biostratigraphic data, however, suggest a somewhat older age. Seafloor erosion, reworking and redeposition, could create this discrepancy between geochronologic and biostratigraphic age determinations. Given that biostratigraphy between the Boreal and Tethyan realms is poorly correlated, the radiometric ages provided by this study could be a stepping stone toward better connecting the Boreal with the Tethyan realm. But further work, on all fronts, is needed. Acknowledgements. Thanks to the UNIS CO2 LAB for access to the drill cores. HS acknowledges the supportof ACS-PRF award # 59965-ND2. References: [1] Koevoets, M.J., Hammer, Ø. & Little, C.T.S. (2019). Norwegian Journal of Geology 99, 1-24. [2] Georgiev, S.V., Stein, H.J., Hannah, J.L., Xu, G.,Bingen, B., & Weiss, H.M. (2017). EPSL, 461, 151-162. [3] Markey, R., Stein, H.J., Hannah, J.L., Georgiev,.V., Pedersen, J.H., & Dons, C.E.(2017). Palaeogeography, Palaeoclimatology, Palaeoecology, 466, 209-220. [4] Koevoets, M.J., Abay, T.B., Hammer, Ø., & Olaussen, S. (2016). Palaeogeography, Palaeoclimatology, Palaeoecology, 449, 266-274

• Zuchuat, Valentin; Augland, Lars Eivind; Jones, Morgan Thomas; Twitchett, Richard; Rodríguez-Tovar, Francisco J. & Hammer, Øyvind [Show all 11 contributors for this article] (2021). Facies changes, volcanism, and mass extinction conundrum: the Permian-Triassic boundary across the Barents Sea Shelf. Full text in Research Archive Show summary

  The most dramatic mass extinction the Earth has ever experienced occurred 252 million years ago, at the end of the Permian. It was likely triggered by the volcanic eruptions and magmatic intrusions associated with the Siberian Traps Large Igneous Province (LIP), leading to dramatic climatic changes, with consequences lasting well into the Early Triassic. Here, we present a summary of the findings from the study of several sedimentary successions distributed across the Barents Sea that spanned the End Permian Mass Extinction (EPME) and the Permian-Triassic boundary. The four studied successions included the renowned Festningen section in the outer part of Isfjorden, western Spitsbergen; the DD-1 core and the associated river section in Deltadalen, central Spitsbergen; a core drilled offshore Kvitøya in northern Svalbard, and a core drilled on the Horda Platform in the Barents Sea. Datasets of various research lines were collected from these sections including sedimentology, organic geochemistry, isotope, geochronology, XRF, mineralogy, ichnology, palaeontology, palynology and digital outcrop data. Historically, the Permian-Triassic boundary exposed today in Svalbard (and at various places across the High Arctic regions) was placed at the very prominent and abrupt facies change occurring between the siliceous mudstones or spiculites of the Kapp Starostin Formation, and the overlying soft, non-siliceous mudstones and siltstones of the Vardebukta and Vikinghøgda formations. The abruptness of this facies change, which also marks the demise of sponges, led to the belief that it represented a hiatus or a gap of several million years, with the uppermost Permian strata missing from the sedimentary record, while the mudstones of the Vardebukta and Vikinghøgda formations were definitely of Lower Triassic age, based on ammonoid biostratigraphy. Hindeodus parvus, the conodont that defines the base of the Triassic, was for the first time identified in Svalbard a few meters above the lithostratigraphic boundary, which is therefore of Upper Permian age. Additionally, our new data show that sedimentation was continuous across this lithostratigraphic boundary. This transition from the Kapp Starostin Formation to the Vardebukta and Vikinghøgda formations was accompanied by a major reorganisation/inversion of the basin(s), but its exact nature remains puzzling. Further, all measured sections record the EPME, which is associated with a 6-8 ‰ δ13CVPDB negative excursion, and measured between the lithostratigraphic and the Permian-Triassic boundaries. These negative isotopic excursions are found in close vicinity to several tephra layers that have been precisely dated at 252.13 ± 0.62 Ma, strongly suggesting a connection to the Siberian Traps LIP event. The mass extinction is also confirmed by the very rapid decreasing of trace fossil abundance and diversity, as anoxia spread across the water from proximal and shallow water to deeper settings. Geochemical and ichnological data indicate the occurrence of several anoxic pulses, intersected by very brief episodes of improved oxygenation levels. It took ca. 145 Kyr for life to recover after the extinction event, based on sedimentation rate calculations. Data also suggest that a shift towards more arid climatic conditions and increased eutrophication on land accompanied the EPME.

• Engelschiøn, Victoria Sjøholt; Hammer, Øyvind; Hurum, Jørn Harald; Bernhardsen, Sofie; Wesenlund, Fredrik & Roberts, Aubrey Jane [Show all 7 contributors for this article] (2020). Large-scale lateral trends in palaeoenvironment and oxygenation in the Middle Triassic Botneheia Fm. on Svalbard. Full text in Research Archive
• Hurum, Jørn Harald; Delsett, Lene Liebe; Hammer, Øyvind & Nakrem, Hans Arne (2020). 15 years with the Spitsbergen Mesozoic Research Group. NGF Abstracts and Proceedings of the Geological Society of Norway. 1, p. 98–98. Full text in Research Archive Show summary

  15 years with the Spitsbergen Mesozoic Research Group Hurum, J. H.*, Delsett, L.L., Hammer, Ø. & Nakrem, H.A. Natural History Museum, University of Oslo, Norway. *Email: j.h.hurum@nhm.uio.no When dinosaurs ruled on land the apex predators in the ocean were marine reptiles. From the Arctic archipelago of Svalbard, the Spitsbergen Mesozoic Research Group has excavated numerous well preserved marine reptile skeletons in order to understand the biology of these animals and the environment they lived in. The work of twelve field seasons since 2004 has made this one of the largest and most productive paleontological research projects in the high Arctic world-wide. The initial eight seasons focused on one of the richest occurrences of Late Jurassic—earliest Cretaceous (c. 150–139 Ma) marine reptiles in the world, and nearly sixty specimens have been collected, together with a diverse assemblage of invertebrates. The last four seasons were spent investigating events further back in time, as Spitsbergen preserves the remains from some of the first marine reptile radiations in the wake of the most devastating extinction in the history of the Earth, at the Permian–Triassic boundary (c. 252 Ma). The international research group published their first scientific results in 2012, followed by a steady stream of publications in the years since. Collectively, it has contributed significantly to the understanding of marine ecosystems at the Jurassic–Cretaceous boundary and is starting to yield results about life’s recovery in the first millions of years after the Permian–Triassic extinction. Outreach has been a major part of the project from the very beginning, both because it is important to share these scientific results with the public, but also because it attracts funding. Alternative financial support and a lot of determination have been crucial components for the success of this long term research project. This has been made possible through cooperation with a local tourist agency and the petroleum industry, grants from the National Geographic Society, income from public lectures and personal sponsors.

• Engelschiøn, Victoria Sjøholt; Wesenlund, Fredrik; Hurum, Jørn Harald; Hammer, Øyvind & Mørk, Atle (2020). East-west depositional trends and fossil preservation in the Middle Triassic Botneheia Fm. on Svalbard. Full text in Research Archive
• Hammer, Øyvind & Jørgensen, Marte Holten (2020). Planter i røntgen. Biolog. ISSN 0801-0722. 2, p. 25–28. Full text in Research Archive
• Engelschiøn, Victoria Sjøholt; Bernhardsen, Sofie; Wesenlund, Fredrik; Hammer, Øyvind; Hurum, Jørn Harald & Mørk, Atle (2019). "Palaeontology of the Middle Triassic dysoxic succession of the Botneheia Fm., Svalbard". Full text in Research Archive
• Engelschiøn, Victoria Sjøholt; Bernhardsen, Sofie; Wesenlund, Fredrik; Hurum, Jørn Harald; Hammer, Øyvind & Mørk, Atle (2019). Anoxia and mass death – a high-resolution biofacies study of the Ladinian (Middle Triassic) Blanknuten Mb., Botneheia Fm. on Edgeøya. Full text in Research Archive
• Mattsson, Tobias; Burchardt, Steffi; Palma, Octavio; Galland, Olivier; Almqvist, Bjarne S.G. & Hammer, Øyvind [Show all 9 contributors for this article] (2019). Magmatic fabrics related to different growth stages of the Cerro Bayo Cryptodome. Full text in Research Archive
• Engelschiøn, Victoria Sjøholt; Hammer, Øyvind; Hurum, Jørn Harald; Wesenlund, Fredrik; Bernhardsen, Sofie & Mørk, Atle (2019). East-west trends in palaeoenvironment and oxygenation in the Middle Triassic Botneheia Fm., Svalbard. Full text in Research Archive
• Engelschiøn, Victoria Sjøholt; Bernhardsen, Sofie; Wesenlund, Fredrik; Hurum, Jørn Harald; Hammer, Øyvind & Roberts, Aubrey Jane [Show all 9 contributors for this article] (2019). Mass death by anoxia - or an exceptional preservation interval? The Middle Triassic bivalve beds of Svalbard. Full text in Research Archive
• Engelschiøn, Victoria Sjøholt; Bernhardsen, Sofie; Wesenlund, Fredrik; Hammer, Øyvind; Hurum, Jørn Harald & Mørk, Atle (2019). The geobiosphere of the Middle Triassic of Svalbard- linking biofacies to geochemistry. Full text in Research Archive
• Jones, Morgan Thomas; Hammer, Øyvind; Bucher, Hugo; Schneebeli-Hermann, Elke; Mather, Tamsin & Svensen, Henrik [Show all 7 contributors for this article] (2019). Are Mercury Anomalies a Reliable Proxy for LIP Volcanism? Examples from the End-Permian and Early Triassic. Full text in Research Archive
• Hurum, Jørn Harald; Nakrem, Hans Arne; Hammer, Øyvind & Delsett, Lene Liebe (2019). Gravplass i verdensformat. GEO. 22(3), p. 12–18. Full text in Research Archive Show summary

  Utgravninger på Svalbard gjennom 15 år har gitt overraskende og sensasjonelle oppdagelser om livets utvikling både i tidlig trias og på overgangen mellom sein jura og tidlig kritt

• Stokke, Ella Wulfsberg; Jones, Morgan Thomas; Hammer, Øyvind & Svensen, Henrik (2018). Geochemical variations during the PETM and later Eocene hyperthermals: investigating a new drill core from Fur, Denmark. Full text in Research Archive
• Stokke, Ella Wulfsberg; Whiteside, Jessica H.; Svensen, Henrik; Hammer, Øyvind & Jones, Morgan Thomas (2018). Linking warming, environmental changes, and volcanic ash falls from onset to recovery of the PETM: investigations from Fur, Denmark. Full text in Research Archive
• Stokke, Ella Wulfsberg; Jones, Morgan Thomas; Hammer, Øyvind & Svensen, Henrik (2018). Geochemistry of Paleocene- Eocene sediments on Fur, Denmark: Linking volcanism and climatic changes. Full text in Research Archive
• Olaussen, Snorre; Senger, Kim; Birchall, Thomas; Braathen, Alvar; Grundvåg, Sten-Andreas & Hammer, Øyvind [Show all 13 contributors for this article] (2018). The Longyearbyen CO2 lab project: lessons learned from a decade of characterizing an unconventional reservoir-caprock system. Full text in Research Archive
• Delsett, Lene Liebe; Koevoets, Maayke Jacqueline; Hammer, Øyvind; Novis, Linn Kristin; Roberts, Aubrey Jane & Druckenmiller, Patrick Scott [Show all 7 contributors for this article] (2017). Marine reptiles from death to discovery. Full text in Research Archive
• Delsett, Lene Liebe; Koevoets, Maayke Jacqueline; Hammer, Øyvind; Novis, Linn Kristin; Roberts, Aubrey Jane & Druckenmiller, Patrick Scott [Show all 7 contributors for this article] (2017). A model for marine reptile taphonomy in the Late Jurassic Slottsmøya Member Lagerstätte. Full text in Research Archive
• Collignon, Marine; Hammer, Øyvind; Fallahi, Mohammad Javad; Lupi, Matteo; Schmid, Daniel Walter & Husein, Alwi [Show all 8 contributors for this article] (2017). Linking the Lusi mud eruption dynamics with regional and global seismic activity: a statistical analysis. Full text in Research Archive
• Nakrem, Hans Arne; Hryniewicz, Krzysztof; Hammer, Øyvind; Little, Crispin T.S. & Kaim, Andrzej (2017). Fossil seep carbonates (Late Jurassic – Late Paleocene) of the greater Barents Shelf area. Full text in Research Archive
• Hurum, Jørn Harald; Økland, Inghild Halvorsen; Ekeheien, Christina; Bratvold, Janne; Nash, Victoria Engelschiøn & Roberts, Aubrey Jane [Show all 14 contributors for this article] (2017). Death and survival in the Early Triassic – Svalbard revisited. Full text in Research Archive
• Mazzini, Adriano; Svensen, Henrik; Forsberg, Carl Fredrik; Linge, Henriette; Lauritzen, Stein-Erik & Haflidason, Haflidi [Show all 9 contributors for this article] (2017). A Climatic Trigger for the Giant Troll Pockmark Field in the Northern North Sea. Full text in Research Archive Show summary

  Pockmarks are seafloor craters usually formed during methane release on continental margins. However, the mechanisms behind their formation and dynamics remain elusive. Here we report detailed investigations on one of the World’s largest pockmark fields located in the Troll region in the northern North Sea. Seafloor investigations show that >7000 pockmarks are present in a ~600 km2 area. A similar density of pockmarks is likely present over a 15,000 km2 region outside our study area. Based on extensive monitoring, coring, geophysical and geochemical analyses, no indications of active gas seepage were found. Still, geochemical data from carbonate blocks collected from these pockmarks indicate a methanogenic origin linked to gas hydrate dissociation and past fluid venting at the seafloor. We have dated the carbonates using the U-Th method in order to constrain the pockmark formation. The carbonates gave an isochron age of 9.59 ± 1.38 ka BP, i.e. belonging to the initial Holocene. Moreover, radiocarbon dating of microfossils in the sediments inside the pockmarks are consistent with the ages derived from the carbonates. Based on pressure and temperature modelling, we show that the last deglaciation could have triggered dissociation of gas hydrates present in the region of the northern part of the Norwegian Channel, causing degassing of 0.26 MtCH4/km2 at the seafloor. Our results stress the importance of external climatic forcing of the dynamics of the seafloor, and the role of the rapid warming following the Younger Dryas in pacing the marine gas hydrate reservoir.

• Hammer, Øyvind; Hurum, Jørn Harald; Roberts, Aubrey Jane; Engelschiøn, Victoria Sjøholt; Nakrem, Hans Arne & Delsett, Lene Liebe [Show all 8 contributors for this article] (2024). EAVP 2024 Short introduction to the vertebrate paleontology of Svalbard, with excursions to the Triassic and Jurassic. Norsk Geologisk Forening. Full text in Research Archive

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