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norskInstitutt for geovitenskap: Recent submissions
Now showing items 501-520 of 1012
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Evolución ambiental de los estuarios del Geoparque de la costa Vasca durante el Holoceno y el Antropoceno
(Chapter; Bokkapittel, 2019-07)In order to reconstruct the environmental evolution of the estuaries in the Basque Coast Geopark at different temporal scales (millennial, centennial, decadal), different long and short cores and surface samples were retrieved and studied. Their multiproxy analysis (metals, foraminifera, pollen and radioisotopes) shows their temporal transformation in response to regional sea-level variations ... -
Experimental grain growth of quartz aggregates under wet conditions and its application to deformation in nature
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-13)Grain growth of quartz was investigated using two quartz samples (powder and novaculite) with water under pressure and temperature conditions of 1.0–2.5 GPa and 800–1100 ∘C. The compacted powder preserved a substantial porosity, which caused a slower grain growth than in the novaculite. We assumed a grain growth law of <i>d<sup>n</sup>−d<sup>n</sup><sub>0</sub>=k</i><sub>0</sub><i>f<sup>r</sup><su ... -
High-resolution underwater laser spectrometer sensing provides new insights into methane distribution at an Arctic seepage site
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-13)Methane (CH4) in marine sediments has the potential to contribute to changes in the ocean and climate system. Physical and biochemical processes that are difficult to quantify with current standard methods such as acoustic surveys and discrete sampling govern the distribution of dissolved CH4 in oceans and lakes. Detailed observations of aquatic CH4 concentrations are required for a better understanding ... -
A 160,000-year-old history of tectonically controlled methane seepage in the Arctic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-07)The geological factors controlling gas release from Arctic deep-water gas reservoirs through seabed methane seeps are poorly constrained. This is partly due to limited data on the precise chronology of past methane emission episodes. Here, we use uranium-thorium dating of seep carbonates sampled from the seabed and from cores drilled at the Vestnesa Ridge, off West Svalbard (79°N, ~1200 m water ... -
Anticlockwise metamorphic pressure–temperature paths and nappe stacking in the Reisa Nappe Complex in the Scandinavian Caledonides, northern Norway: evidence for weakening of lower continental crust before and during continental collision
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019)This study investigates the tectonostratigraphy and metamorphic and tectonic evolution of the Caledonian Reisa Nappe Complex (RNC; from bottom to top: Vaddas, Kåfjord, and Nordmannvik nappes) in northern Troms, Norway. Structural data, phase equilibrium modelling, and U-Pb zircon and titanite geochronology are used to constrain the timing and pressure–temperature (<i>P–T</i>) conditions of deformation ... -
The Origin of Gas Seeps in the Northern Adriatic Sea
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06)A multidisciplinary approach has been used for the first time to study the widespread occurrence of hydrocarbon seeps in the northern Adriatic Sea. Geological, geophysical and geochemical analyses were performed to identify and characterize the gas-charged fluids occurring throughout the Plio-Quaternary succession, and to date the shallow gas seeping at three leakage sites. The analysis of CHIRP, ... -
Palaeoceanographic reconstruction of surface-ocean changes in the southern Norwegian Sea for the last ~130,000 years based on diatoms and with comparison to foraminiferal records
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-28)Fossil marine diatom assemblages in a sediment core from the central northern Faroe slope in the Norwegian Sea were used to reconstruct palaeoceanographic changes in the surface water mixed layer from the last ~130,000 years (Marine Isotope Stage (MIS) 6/5 transition to MIS 1 (including the Eemian and Holocene interglacials) and to compare the results with previously published results on planktic ... -
Morphological evidence for marine ice stream shutdown, central Barents Sea
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-02)Marine-based ice streams are responsible for a significant proportion of the ice mass loss from the present-day Greenland Ice Sheet, East Antarctic Ice Sheet (EAIS) and West Antarctic Ice Sheet (WAIS) but the processes controlling their initiation, evolution and shutdown remain elusive, hindering our understanding of how existing ice masses will respond to predicted future warming. The exposed beds ... -
Reviewing the Cenozoic Net Erosion of the Barents Sea Shelf
(Conference object; Konferansebidrag, 2019-01) -
Evidence of Isotopic Fractionation During Vapor Exchange Between the Atmosphere and the Snow Surface in Greenland
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-18)Several recent studies from both Greenland and Antarctica have reported significant changes in the water isotopic composition of near‐surface snow between precipitation events. These changes have been linked to isotopic exchange with atmospheric water vapor and sublimation‐induced fractionation, but the processes are poorly constrained by observations. Understanding and quantifying these processes ... -
Fracture-controlled fluid transport supports microbial methane-oxidizing communities at Vestnesa Ridge
(Journal article; Peer reviewed, 2019-05-29)We report a rare observation of a mini-fracture in near-surface sediments (30 cm below the seafloor) visualized using a rotational scanning X-ray of a core recovered from the Lomvi pockmark, Vestnesa Ridge, west of Svalbard (1200 m water depth). Porewater geochemistry and lipid biomarker signatures revealed clear differences in the geochemical and biogeochemical regimes of this core compared with ... -
Organic Matter Sources in North Atlantic Fjord Sediments
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-31)To better constrain the global carbon cycle fundamental knowledge of the role of carbon cycling on continental margins is crucial. Fjords are particularly important shelf areas for carbon burial due to relatively high sedimentation rates and high organic matter fluxes. As terrigenous organic matter is more resistant to remineralization than marine organic matter, a comprehensive knowledge of the ... -
Constraints on Gas Hydrate Distribution and Morphology in Vestnesa Ridge, Western Svalbard Margin, Using Multicomponent Ocean‐Bottom Seismic Data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-26)Gas hydrates occur within sediments on the western Svalbard continental margin and the Vestnesa Ridge, a large sediment drift that extends in a west‐north‐west direction from the margin towards the mid‐ocean ridge. We acquired multi‐component ocean‐bottom seismic (OBS) data at ten locations on the crest area of the eastern segment of the Vestnesa Ridge, an area with active gas seepage. P and S‐wave ... -
Deep ocean 14C ventilation age reconstructions from the Arctic Mediterranean reassessed
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-13)The present-day ocean ventilation in the Arctic Mediterranean (Nordic Seas and Arctic Ocean), via transformation of northward inflowing warm Atlantic surface water into cold deep water, affects regional climate, atmospheric circulation and carbon storage in the deep ocean. Here we study the glacial evolution of the Arctic Mediterranean circulation and its influence on glacial climate using ... -
Formation Conditions and 40Ar/39Ar Age of the Gem-Bearing Boqueirão Granitic Pegmatite, Parelhas, Rio Grande do Norte, Brazil
(Journal article; Peer reviewed, 2019-04-15)The Boqueirão granitic pegmatite, alias Alto da Cabeça pegmatite, is situated in Borborema Pegmatitic Province (BPP) in Northeast Brazil. This pegmatitic province hosts globally important reserves of tantalum and beryllium, as well as significant quantities of gemstones, including aquamarine, morganite, and the high-quality turquoise-blue “Paraíba Elbaite”. The studied lithium-cesium-tantalum Boqueirão ... -
The Role of Magmatic and Hydrothermal Fluids in the Formation of the Sasa Pb-Zn-Ag Skarn Deposit, Republic of Macedonia
(Journal article; Peer reviewed, 2018-11-29)The Sasa Pb-Zn-Ag deposit belongs to the group of distal base metal skarn deposits. The deposit is located within the Serbo-Macedonian massif, a metamorphosed crystalline terrain of Precambrian to Paleozoic age. The mineralization, hosted by Paleozoic marbles, shows a strong lithological control. It is spatially and temporally associated with the calc-alkaline to shoshonitic post-collisional magmatism ... -
Postglacial relative sea level change and glacier activity in the early and late Holocene: Wahlenbergfjorden, Nordaustlandet, Svalbard
(Journal article; Peer reviewed, 2019-05-01)Sediment cores from Kløverbladvatna, a threshold lake in Wahlenbergfjorden, Nordaustlandet, Svalbard were used to reconstruct Holocene glacier fluctuations. Meltwater from Etonbreen spills over a threshold to the lake, only when the glacier is significantly larger than at present. Lithological logging, loss-on-ignition, ITRAX scanning and radiocarbon dating of the cores show that Kløverbladvatna ... -
Identifying the Controlling Factors on Variable Glacial Modification of Bedrock Dominated Areas in Kongsfjorden, Svalbard
(Master thesis; Mastergradsoppgave, 2018-07-05)This thesis aims to better understand the variability of glacial erosion along glacial troughs located in high latitude settings, through a case study of Kongsfjorden, Svalbard. The research question of this thesis is to identify the controlling factors on variable glacial modification of the bedrock dominated areas in Kongsfjorden. Fieldwork was conducted to analyze bedrock structures and ... -
Morfologisk og sedimentologisk studium av det moderne og hevede Storfjorddeltaet, Troms
(Master thesis; Mastergradsoppgave, 2018-07-05)Denne oppgaven består i å undersøke det aktive Storfjorddeltaet med hensyn på morfologi og sedimentologi. Den hevede delen av deltaet ble også undersøkt ved 3 snitt for å finne ut hvordan deltaet hadde progradert for omtrent 3000 år siden og frem til i dag. Kartlegging og flybilder ble brukt, i tillegg til siling av prøver og datering av materiale. Resultatet ble at deltaet er klassifisert som et ... -
Source of CO2 in large Talc-Carbonate veins in serpentinites of the Zermatt-Saas Fee unit
(Master thesis; Mastergradsoppgave, 2018-07-03)The Zermatt-Saas Fee zone represents an ophiolitic sequence within the Western Alps derived from the paleo ocean Liguro-Piemontaise. The melting of the Unterer Theodulgletcher glacier newly uncovered some Tc-Mgs and Atg-Dol veins within serpentinite host rock. Both the serpentinite and veins are fresh as they have been protected from weathering by the glacier, which makes this area ideal for ...
