Artikler, rapporter og annet (geovitenskap): Recent submissions
Now showing items 161-180 of 755
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Contrasting Neogene–Quaternary continental margin evolution offshore mid-north Norway: Implications for source-to-sink systems
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-12-22)The Neogene–Quaternary development of the ∼700 km long mid-Norwegian and Lofoten–Vesterålen continental margin is reconstructed using a dense grid of 2D seismic data and exploration wellbores. Overall, widespread ocean current-controlled contourite drifts built up along the whole margin segment from the mid-Miocene onwards (c. 11 Ma, Kai Formation). The onset (c. 8.8 Ma) of a large inner shelf ... -
Structural and metamorphic history of the Leech river shear zone, Vancouver Island, British Columbia
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-13)The Leech River Shear Zone (LRSZ) on southern Vancouver Island separates the metasedimentary schists of the Leech River Complex (LRC) from the accreted oceanic plateau of the Siletz-Crescent terrane. The juxtaposition of these rock units suggests a possible origin as a subduction plate boundary but tectonic context of the LRSZ has yet to be fully established. We present field, microstructural, ... -
Active Nordic Seas deep-water formation during the last glacial maximum
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-24)The Nordic Seas are the primary location where the warm waters of the North Atlantic Current densify to form North Atlantic Deep Water, which plays a key part in the modern Atlantic Meridional Overturning Circulation. The formation of dense water in the Nordic Seas and Arctic Ocean and resulting ocean circulation changes were probably driven by and contributed to the regional and global climate of ... -
A stable isotope assay with 13C-labeled polyethylene to investigate plastic mineralization mediated by Rhodococcus ruber
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-30)Methods that unambiguously prove microbial plastic degradation and allow for quantification of degradation rates are necessary to constrain the influence of microbial degradation on the marine plastic budget. We developed an assay based on stable isotope tracer techniques to determine microbial plastic mineralization rates in liquid medium on a lab scale. For the experiments, <sup>13</sup>C-labeled ... -
Methane release from open leads and new ice following an Arctic winter storm event
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-03)We examine an Arctic winter storm event, which led to ice break–up, the formation of open leads, and the subsequent freezing of these leads. The methane (CH<sub>4</sub>) concentration in under–ice surface water before and during the storm event was 8–12 nmol L<sup>−1</sup>, which resulted in a potential sea–to–air CH<sub>4</sub> flux ranging from +0.2 to +2.1 mg CH<sub>4</sub> m<sup>−2</sup> ... -
Catchment characteristics and seasonality control the composition of microbial assemblages exported from three outlet glaciers of the Greenland Ice Sheet
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-29)Glacial meltwater drains into proglacial rivers where it interacts with the surrounding landscape, collecting microbial cells as it travels downstream. Characterizing the composition of the resulting microbial assemblages in transport can inform us about intra-annual changes in meltwater flowpaths beneath the glacier as well as hydrological connectivity with proglacial areas. Here, we investigated ... -
Digitising Svalbard’s geology: the Festningen digital outcrop model
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-10)The renowned Festningen section in the outer part of Isfjorden, western Spitsbergen, offers a c. 7 km-long nearly continuous stratigraphic section of Lower Carboniferous to Cenozoic strata, spanning nearly 300 million years of geological history. Tectonic deformation associated with the Paleogene West-Spitsbergen-Fold-and-Thrust belt tilted the strata to near-vertical, allowing easy access to the ... -
An annual profile of the impacts of simulated oil spills on the Northeast Arctic cod and haddock fisherie
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-10)We simulate the combined natural and pollutant-induced survival of early life stages of NEA cod and haddock, and the impact on the adult populations in response to the time of a major oil spill in a single year. Our simulations reveal how dynamic ocean processes, controlling both oil transport and fate and the frequency of interactions of oil with drifting fish eggs and larvae, mediate the magnitude ... -
Hot Vents Beneath an Icy Ocean: The Aurora Vent Field, Gakkel Ridge, Revealed
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-28)Evidence of hydrothermal venting on the ultra-slow spreading Gakkel Ridge in the Central Arctic Ocean has been available since 2001, with first visual evidence of black smokers on the Aurora Vent Field obtained in 2014. But it was not until 2021 that the first ever remotely operated vehicle (ROV) dives to hydrothermal vents under permanent ice cover in the Arctic were conducted, enabling the ... -
The extreme yet transient nature of glacial erosion
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-30)Ice can sculpt extraordinary landscapes, yet the efficacy of, and controls governing, glacial erosion on geological timescales remain poorly understood and contended, particularly across Polar continental shields. Here, we assimilate geophysical data with modelling of the Eurasian Ice Sheet — the third largest Quaternary ice mass that spanned 49°N to 82°N — to decipher its erosional footprint during ... -
Multiproxy investigation of the last 2,000 years BP marine paleoenvironmental record along the western Spitsbergen margin
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-01)A reconstruction of the last 2,000 years BP of environmental and oceanographic changes on the western margin of Spitsbergen was performed using a multidisciplinary approach including the fossil assemblages of diatoms, planktic and benthic foraminifera and calcareous nannofossils and the use of geochemistry (X-ray fluorescence spectroscopy, X-ray diffraction). We identified two warm periods ... -
Quartz rheology constrained from constant-load experiments: Consequences for the strength of the continental crust
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-09-21)The mechanical properties of quartz are fundamental to control the plastic behaviour of the continental crust. Our understanding of quartz rheology is still limited in the following respects: i) the large variability of flow law parameters in the earlier literature (stress exponent n = 4 to ≤ 2 and activation energy Q = 120 to 242 kJ/mol), and ii) the difficulty to identify the rate-limiting deformation ... -
Mechanical properties and recrystallization of quartz in presence of H<inf>2</inf>O: Combination of cracking, subgrain rotation and dissolution-precipitation processes
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-05-21)Natural quartzite samples, as-is and with 0.1 wt% of added H<sub>2</sub>O, have been deformed up to ∼30% bulk strain in axial shortening experiments with constant strain rate of ∼10<sup>−6</sup> s<sup>−1</sup> at 900 °C and 1 GPa, and in strain rate stepping ∼10<sup>−5</sup> to ∼10<sup>−7</sup> s<sup>−1</sup> at 900 °C and 1–1.5 GPa, in order to investigate the role of H<sub>2</sub>O in deformation ... -
Late Quaternary terrigenous plant and coaly fragments found at Vestnesa Ridge, Fram Strait: implications for postglacial plant colonization at Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-23)One of four marine cores of glacial sediments collected from a water depth of about 1200 m at Vestnesa Ridge (west of Svalbard) contained small fragments of coal, charcoal and moss. This material was restricted to a single level, and 14C dating of bivalves both above and below indicates an age of c. 18.0–15.5 kyr BP. Chemical analyses of the coal indicate that the provenance area was from the northern ... -
Structural and fluid-migration control on hill-hole pair formation: Evidence from high-resolution 3D seismic data from the SW Barents Sea
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-11)Hill-hole pairs are subglacial landforms consisting of thrust-block hills and associated source depressions. Formed by evacuation of material where ice sheets have been locally frozen to the substrate, they give insights into paleo-ice-sheet dynamics. The aim of this study was to document the relationships between ancient hill-hole pairs identified on a buried glacial unconformity with the structure ... -
Climatic impacts on an Arctic lake since 1300 AD: a multi-proxy lake sediment reconstruction from Prins Karls Forland, Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-31)On the remote Arctic archipelago of Svalbard, there is increasing evidence of environmental impacts from climate change. The analysis of lake sedimentary records can be used to assess how strongly these recent changes have altered lake ecosystems. Sediments deposited during the last millennium from Lake Blokkvatnet, Prins Karls Forland, were analysed using a multiproxy approach, including stable ... -
Petrogenesis of zoned and unzoned mafic pegmatites: An insight from the Palaeoproterozoic mafic-ultramafic Hamn intrusion, Northern Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-03)Mafic pegmatites have been reported from various geological environments, including ophiolites, layered magmatic intrusions, and volcanic arcs, but their petrogenesis stayed poorly constrained. This study brings new mineralogical and geochemical data obtained from unzoned and zoned gabbroic pegmatites hosted by the 1.8 Ga mafic-ultramafic Hamn intrusion, Northern Norway, with an aim to improve our ... -
Volcanically hosted venting with indications of ultramafic influence at Aurora hydrothermal field on Gakkel Ridge
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-31)The Aurora hydrothermal system, Arctic Ocean, hosts active submarine venting within an extensive field of relict mineral deposits. Here we show the site is associated with a neovolcanic mound located within the Gakkel Ridge rift-valley floor, but deep-tow camera and sidescan surveys reveal the site to be ≥100 m across—unusually large for a volcanically hosted vent on a slow-spreading ridge and more ... -
Northeast Greenland (79.4 °N): Ice-free shelf edge around the Last Glacial Maximum 25.5-17.5 ka
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-16)The size of the last glacial ice sheet on the Northeast (NE) Greenland shelf and its interaction with ocean circulation have been the subject of debate. Here we provide insights into the extent of the ice sheet around the Last Glacial Maximum (LGM) and investigate timing and strength of changes in the flow of Atlantic Water. The study is based on a multiproxy investigation of a marine sediment core, ... -
Biogeochemistry and timing of methane-derived carbonate formation at Leirdjupet fault complex, SW Barents sea
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-25)The origin of modern seafloor methane emissions in the Barents Sea is tightly connected to the glacio-tectonic and oceanographic transformations following the last ice age. Those regional events induced geological structure re-activation and destabilization of gas hydrate reservoirs over large areas of the European continental margins, sustaining widespread fluid plumbing systems. Despite the ...