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norskInstitutt for geovitenskap: Nye registreringer
Viser treff 381-400 av 1102
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Historical contingency impacts on community assembly and ecosystem function in chemosynthetic marine ecosystems
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-07)Predicting ecosystem functioning requires an understanding of the mechanisms that drive microbial community assembly. Many studies have explored microbial diversity extensively and environmental factors are thought to be the principal drivers of community composition. Community assembly is, however, also influenced by past conditions that might affect present-day assemblages. Historical events, ... -
Deep ocean storage of heat and CO2 in the Fram Strait, Arctic Ocean during the last glacial period
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-19)The Fram Strait is the only deep gateway between the Arctic Ocean and the Nordic Seas and thus is a key area to study past changes in ocean circulation and the marine carbon cycle. Here, we study deep ocean temperature, δ18O, carbonate chemistry (i.e., carbonate ion concentration [CO32−]), and nutrient content in the Fram Strait during the late glacial (35,000–19,000 years BP) and the Holocene based ... -
The geochemical signature of Cu mineralisation preserved in stream sediments from the Alta-Kvænangen Tectonic Window, Northern Norway
(Master thesis; Mastergradsoppgave, 2021-06-13)The Paleoproterozoic Greenstone Belts of Fennoscandia are metamorphosed and deformed volcanic and sedimentary basins with a high metallic ore potential. One of those, the Alta-Kvænangen Tectonic Window (AKTW), is exposed as a window below the Caledonides of Northern Norway. The Kåfjord area located within the AKTW hosts numerous known Cu occurrences. The Cu mineralisation in Kåfjord occurs mostly ... -
Geochemical characteristics of sediment- and mafic rock-hosted Cu deposits in the Kåfjord area, Alta-Kvænangen Tectonic Window, Northern Norway
(Mastergradsoppgave; Master thesis, 2021-06-15)The Precambrian Alta-Kvænangen Tectonic Window (AKTW) located in the northern part of Norway, hosts different types of copper mineralization. Some of Cu occurrences have been previously mined, but their geochemical and stable isotope characteristics have not been a subject of detailed investigations, and therefore the relevant ore-forming processes are still poorly understood. This study, brings new ... -
The Mjølnir Impact Crater in the central Barents Sea - a potential hydrocarbon system?
(Master thesis; Mastergradsoppgave, 2020-05-15)A meteor impact event on the Bjameland Platform in the Norwegian Barents Sea about 142 ± 2.6 million years ago formed the Mjølnir Impact Crater. The structure has diameter of 40 km impacting the Mesozoic stratigraphy, and has previously been investigated with emphasis on the dynamics of the impact, the structure formation, sedimentation and post-impact tectonics. Impact structures have proven to be ... -
A Continuous Seismostratigraphic Framework for the Western Svalbard-Barents Sea Margin Over the Last 2.7 Ma: Implications for the Late Cenozoic Glacial History of the Svalbard-Barents Sea Ice Sheet
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-14)Here we present a high-resolution, continuous seismostratigraphic framework that for the first time, connects the over 1,000 km long western Svalbard-Barents Sea margin and covers the last ∼2.7 million years (Ma). By exploiting recent improvements in chronology, we establish a set of reliable age fix-points from available boreholes along the margin. We then use a large 2-D seismic database to extend ... -
Seasonal sea ice persisted through the Holocene Thermal Maximum at 80°N
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-15)The cryospheric response to climatic warming responsible for recent Arctic sea ice decline can be elucidated using marine geological archives which offer an important long-term perspective. The Holocene Thermal Maximum, between 10 and 6 thousand years ago, provides an opportunity to investigate sea ice during a warmer-than-present interval. Here we use organic biomarkers and benthic foraminiferal ... -
Neoglacial plateau ice cap behaviour in Central Spitsbergen constrained by subglacially preserved vegetation.
(Mastergradsoppgave; Master thesis, 2021-06-15)Cold-based glacial ice is well known to preserve underlying landforms produced by earlier processes but can also preserve pre-existing organic material and vegetated ground. With current rapid climate warming, overall glacier retreat in the Arctic is exposing formerly ice-buried in situ vegetation at the margin of cold-based ice bodies. Radiocarbon dating of this vegetation constrains the timing of ... -
Shell density of planktonic foraminifera and pteropod species Limacina helicina in the Barents Sea: Relation to ontogeny and water chemistry
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-28)Planktonic calcifiers, the foraminiferal species <i>Neogloboquadrina pachyderma</i> and <i>Turborotalita quinqueloba</i>, and the thecosome pteropod <i>Limacina helicina</i> from plankton tows and surface sediments from the northern Barents Sea were studied to assess how shell density varies with depth habitat and ontogenetic processes. The shells were measured using X-ray microcomputed tomography ... -
Effect of pressure on the deformation of quartz aggregates in the presence of H2O
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-17)Quartzite samples of high purity with a grain size of ~200 μm have been experimentally deformed by coaxial shortening in a solid medium apparatus at 900 °C and at confining pressures ranging from 0.6 to 2 GPa. Most samples have been shortened by ~30% with 0.1 wt% added H<sub>2</sub>O. The samples deformed dominantly by crystal plasticity (dislocation creep), and there is a systematic decrease of ... -
Environmental evolution of the Basque Coast Geopark estuaries (southern Bay of Biscay) during the last 10,000 years
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-21)In order to reconstruct the environmental evolution of the Deba and Urola estuaries located in the Basque Coast Geopark at millennial, centennial and decadal timescales, four long boreholes, three short cores and twelve surface samples were studied. Multiproxy analysis (foraminifera, trace metals and radioisotopes) shows the temporal transformation of these estuaries in response to regional driving ... -
Gas migration and sealing modelling in the Haapet Dome area, Norwegian Barents Sea - analysis of seismic anomalies and water column data
(Master thesis; Mastergradsoppgave, 2020-05-15)Seismic interpretation, water column data, and well information have enabled a thorough review of shallow amplitude anomalies and subsurface faulting, in conjunction with possible migration pathways in the Haapet Dome area. The processed water column data from the MAREANO-program was presented and evaluated in accordance with potential gas leakage from the seafloor. Water column imaging illustrates ... -
Storage and export of microbial biomass across the western Greenland Ice Sheet
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-25)The Greenland Ice Sheet harbours a wealth of microbial life, yet the total biomass stored or exported from its surface to downstream environments is unconstrained. Here, we quantify microbial abundance and cellular biomass flux within the near-surface weathering crust photic zone of the western sector of the ice sheet. Using groundwater techniques, we demonstrate that interstitial water flow is slow ... -
Sea ice thickness from air-coupled flexural waves
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-28)Air-coupled flexural waves (ACFWs) appear as wave trains of constant frequency that arrive in advance of the direct air wave from an impulsive source travelling over a floating ice sheet. The frequency of these waves varies with the flexural stiffness of the ice sheet, which is controlled by a combination of thickness and elastic properties. We develop a theoretical framework to understand these ... -
Dynamic and history of methane seepage in the SW Barents Sea: new insights from Leirdjupet Fault Complex
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-23)Methane emissions from Arctic continental margins are increasing due to the negative effect of global warming on ice sheet and permafrost stability, but dynamics and timescales of seafloor seepage still remain poorly constrained. Here, we examine sediment cores collected from an active seepage area located between 295 and 353 m water depth in the SW Barents Sea, at Leirdjupet Fault Complex. The ... -
Seasonal shifts of microbial methane oxidation in Arctic shelf waters above gas seeps
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-07)The Arctic Ocean subseabed holds vast reservoirs of the potent greenhouse gas methane (CH<sub>4</sub>), often seeping into the ocean water column. In a continuously warming ocean as a result of climate change an increase of CH<sub>4</sub> seepage from the seabed is hypothesized. Today, CH<sub>4</sub> is largely retained in the water column due to the activity of methane-oxidizing bacteria (MOB) that ... -
Reconstruction of the paleocenaography west of Lofoten during the Last Glacial Maximum
(Master thesis; Mastergradsoppgave, 2021-05-15)<p>A 513 cm long sediment core from the Lofoten Contourite Drift at the continental slope west of the Lofoten Islands has been investigated. The aim was to reconstruct the paleoceanography during the Last Glacial Maximum (LGM). The Lofoten Contourite drift was relatively protected by the Lofoten Islands from the ice streams of the Scandinavian Ice Sheet during LGM. <p>An age model was constructed ... -
Large subglacial source of mercury from the southwestern margin of the Greenland Ice Sheet
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-24)The Greenland Ice Sheet is currently not accounted for in Arctic mercury budgets, despite large and increasing annual runoff to the ocean and the socio-economic concerns of high mercury levels in Arctic organisms. Here we present concentrations of mercury in meltwaters from three glacial catchments on the southwestern margin of the Greenland Ice Sheet and evaluate the export of mercury to downstream ... -
Testing miniaturized extraction chromatography protocols for combined 87Sr/86Sr and δ88/86Sr analyses of pore water by MC‐ICP‐MS
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-04)We tested two miniaturized extraction chromatography protocols for strontium isolation based on 300 μL (Protocol 1) and 30 μL (Protocol 2) column volumes of Sr‐Spec resin, for the simultaneous determination of 87Sr/86Sr and δ88/86Sr by MC‐ICP‐MS. The accuracy and precision of the Sr isotope ratios have been evaluated by analyzing JCt‐1 and SRM 1640a reference materials, resulting in a reproducibility ... -
The Role of Mineral Assemblages in the Environmental Impact of Cu-Sulfide Deposits: A Case Study from Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-12)Metallic mineral deposits represent natural geochemical anomalies of economically valuable commodities but, at the same time, their weathering may have negative environmental implications. Cu-sulfide mineral deposits have been recognized as deposits with a particularly large environmental footprint. However, different Cu deposits may result in significantly different environmental impacts, mostly ...
