Now showing items 181-200 of 729

    • Physical conditions and frictional properties in the source region of a slow-slip event 

      Arnulf, Adrien F.; Biemiller, James; Lavier, Luc; Wallace, Laura M.; Bassett, Dan; Henrys, Stuart; Pecher, Ingo; Crutchley, Gareth; Plaza-Faverola, Andreia (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-06)
      Recent geodetic studies have shown that slow-slip events can occur on subduction faults, including their shallow (<15 km depth) parts where tsunamis are also generated. Although observations of such events are now widespread, the physical conditions promoting shallow slow-slip events remain poorly understood. Here we use full waveform inversion of controlled-source seismic data from the central ...
    • Reconstruction of a volcano-sedimentary environment shared by the Porongos and Várzea do Capivarita complexes at 790 Ma, Dom Feliciano Belt, southern Brazil 

      Battisti, Matheus Ariel; Bitencourt, Maria de Fatima; Schmitt, Renata da Silva; Nardi, Lauro Valentim Stoll; Martil, Mariana Maturano Dias; De Toni, Giuseppe Betino; Pimentel, Márcio Martins; Armstrong, Richard; Konopásek, Jiří (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-22)
      This work investigates the pre-collisional (before ca. 650 Ma) history of the Dom Feliciano Belt in southernmost Brazil through geochronological and zircon oxygen isotope study. U–Pb SHRIMP dating of two orthogneiss samples from the Várzea do Capivarita Complex and one metarhyolite sample from the Porongos Complex yielded crystallisation ages of 786 ± 5 Ma, 780 ± 10 Ma and 787 ± 5 Ma, respectively. ...
    • Glacially Induced Stress Across the Arctic From the Eemian Interglacial to the Present—Implications for Faulting and Methane Seepage 

      Vachon, Remi Elie Celestin; Schmidt, P.; Lund, Bjorn; Plaza-Faverola, Andreia; Patton, Henry; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-28)
      Strong compressive and shear stresses generated by glacial loading and unloading have a direct impact on near-surface geological processes. Glacial stresses are constantly evolving, creating stress perturbations in the lithosphere that extend significant distances away from the ice. In the Arctic, periodic methane seepage and faulting have been recurrently associated with glacial cycles. However, ...
    • Rapid post-glacial bedrock weathering in coastal Norway 

      Andersen, Jane Lund; Margreth, Annina; Fredin, Ola; Linge, Henriette; Goodfellow, Bradley W.; Faust, Johan Christoph; Knies, Jochen; Solbakk, Terje; Brook, Edward J.; Scheiber, Thomas; van der Lelij, Roelant; Burki, Valentin Josef; Rubensdotter, Brita Lena Eleonor Fredin; Himmler, Tobias; Yesilyurt, Serdar; Christl, Marcus; Vockenhuber, Christof; Akcar, Naki (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-26)
      Quantifying bedrock weathering rates under diverse climate conditions is essential to understanding timescales of landscape evolution. Yet, weathering rates are often difficult to constrain, and associating a weathered landform to a specific formative environment can be complicated by overprinting of successive processes and temporally varying climate. In this study, we investigate three sites ...
    • MIS 3 age of the Veiki moraine in N Sweden – Dating the landform record of an intermediate-sized ice sheet in Scandinavia 

      Alexanderson, Helena; Hättestrand, Martina; Lindqvist, Mimmi A.; Sigfúsdóttir, Thorbjörg (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-14)
      The Veiki moraine in northern Sweden, a geomorphologically distinct landscape of ice-walled lake plains, has been interpreted to represent the former margin of an intermediate-sized pre–Last Glacial Maximum (LGM) Fennoscandian ice sheet, but its age is debated as either marine isotope stage (MIS) 5c or MIS 3. We have applied optically stimulated luminescence (OSL) and radiocarbon dating to four sites ...
    • Combined X-Ray Computed Tomography and X-Ray Fluorescence Drill Core Scanning for 3-D Rock and Ore Characterization: Implications for the Lovisa Stratiform Zn-Pb Deposit and Its Structural Setting, Bergslagen, Sweden 

      Luth, Stefan; Sahlström, Fredrik; Bergqvist, Mikael; Hansson, Alexander; Lynch, Edward P.; Sädbom, Stefan; Jonsson, Erik; Andersson, Stefan S.; Arvanitidis, Nikolaos (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-29)
      We present the results of a pilot study that integrates automated drill core scanning technology based on simultaneous X-ray computed tomography (XCT) and X-ray fluorescence (XRF) analyses to provide high-spatialresolution (<0.2 mm) information on 3-D rock textures and structures, chemical composition, and density. Testing of its applicability for mineral exploration and research was performed by ...
    • Tectonic evolution of the Indio Hills segment of the San Andreas fault in southern California, southwestern USA 

      Koehl, Jean-Baptiste P.; Bergh, Steffen Gunnar; Sylvester, Arthur G. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-01)
      Transpressional uplift domains of inverted Pliocene–Pleistocene basin fill along the San Andreas fault zone in Coachella Valley, southern California (USA), are characterized by fault linkage and segmentation and deformation partitioning. The Indio Hills wedge-shaped uplift block is located in between two boundary fault strands, the Indio Hills fault to the northeast and the main San Andreas fault ...
    • Ammonium and Sulfate Assimilation Is Widespread in Benthic Foraminifera 

      LeKieffre, Charlotte; Jauffrais, Thierry; Bernhard, Joan M.; Filipsson, Helena L.; Schmidt, Christiane; Roberge, Helene; Maire, Olivier; Panieri, Giuliana; Geslin, Emmanuelle; Meibom, Anders (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-20)
      Nitrogen and sulfur are key elements in the biogeochemical cycles of marine ecosystems to which benthic foraminifera contribute significantly. Yet, cell-specific assimilation of ammonium, nitrate and sulfate by these protists is poorly characterized and understood across their wide range of species-specific trophic strategies. For example, detailed knowledge about ammonium and sulfate assimilation ...
    • Evolution of the Gállojávri ultramafic intrusion from U-Pb zircon ages and Rb-Sr, Sm-Nd and Lu-Hf isotope systematics 

      Orvik, Alf Andre; Slagstad, Trond; Sørensen, Bjørn Eske; Millar, Ian; Hansen, Harald (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-05)
      The Karasjok–Central Lapland Greenstone Belt is one of the largest Palaeoproterozoic greenstone belts in the Fennoscandian Shield and includes multiple (ultra)mafic intrusions, some with notable ore reserves, formed during three episodes at 2.44, 2.22 and 2.05 Ga. This study presents new mineralogical, geochronological and isotopic data for the Gállojávri ultramafic intrusion, in the Karasjok ...
    • Evolution of ore-forming fluids in a post-collisional porphyry Cu-Au system: A case study from the Bučim deposit, Republic of North Macedonia 

      Strmic Palinkas, Sabina; Perkovic, Ivor; Čobić, Andrea; Jurkovic, Iva; Tasev, Goran; Serafimovski, Todor; Spangenberg, Jorge E. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-04-27)
      The Bučim porphyry Cu-Au deposit is situated in the westernmost part of the Serbo-Macedonian Massif, Republic of North Macedonia. The deposit is hosted by Precambrian gneisses with tectonically imbedded rare lenses of Palaeozoic amphibolites. The mineralization is spatially associated with intrusions of andesitic to trachyandesitic magmatic bodies. The geochemical signature of the intrusions and ...
    • Upper cretaceous-paleogene stratigraphy and development of the Mímir High, Vøring transform margin, Norwegian Sea 

      Polteau, Stephane; Planke, Sverre; Zastrozhnov, Dmitrii; Abdelmalak, Mohamed Mansour; Lebedeva-Ivanova, Nina; Eckhoff Planke, Ellen; Svensen, Henrik; Mazzini, Adriano; Gernigon, Laurent; Myklebust, Reidun; Kjølhamar, Bent; Pedersen, Rolf B.; Sandstå, Nils Rune; Bünz, Stefan (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-19)
      Transform margins represent strike-slip type of plate boundaries that form during continental breakup and initial ocean opening. They are often characterized by margin-parallel highs with exposed pre- and syn-rift sequences. The Vøring Transform Margin, offshore mid-Norway, initiated in the earliest Eocene during the opening of the NE Atlantic. Here, 2D seismic reflection data reveal a transform ...
    • A Phenomenographic Analysis Of Students’ Experience Of Geological Time 

      Lundqvist, Jennie Mari; Svensson, Kim; Ljung, Karl; Eriksson, Urban; Eriksson, Moa (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-01)
      Geological time is by many geoscience instructors considered a threshold concept for geoscience students, being a central concept for how we experience geosceince phenomena that takes place on a spatio-temporal scale ranging from micro (e.g. cloud formation) to macro (e.g. plate tectonics). If one wishes to understand geoscience phenomena that goes beyond human perception, one must move from the ...
    • The role of ocean and atmospheric dynamics in the marine-based collapse of the last Eurasian Ice Sheet 

      Sejrup, Hans Petter; Hjelstuen, Berit Oline Blihovde; Patton, Henry; Esteves, Mariana; Winsborrow, Monica; Rasmussen, Tine Lander; Andreassen, Karin Marie; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-05-19)
      Information from former ice sheets may provide important context for understanding the response of today’s ice sheets to forcing mechanisms. Here we present a reconstruction of the last deglaciation of marine sectors of the Eurasian Ice Sheet, emphasising how the retreat of the Norwegian Channel and the Barents Sea ice streams led to separation of the British-Irish and Fennoscandian ice sheets at ...
    • Permafrost in monitored unstable rock slopes in Norway-New insights from temperature and surface velocity measurements, geophysical surveying, and ground temperature modelling 

      Etzelmüller, Bernd; Czekirda, Justyna; Magnin, Florence; Duvillard, Pierre-Allain; Ravanel, Ludovic; Malet, Emanuelle; Aspaas, Andreas Grøvan; Kristensen, Lene; Skrede, Ingrid; Majala, Gudrun D.; Jacobs, Benjamin; Leinauer, Johannes; Hauck, Christian; Hilbich, Christin; Böhme, Martina; Hermanns, Reginald; Eriksen, Harald Øverli; Lauknes, Tom Rune; Krautblatter, Michael; Westermann, Sebastian (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-01)
      The warming and subsequent degradation of mountain permafrost within alpine areas represent an important process influencing the stability of steep slopes and rock faces. The unstable and monitored slopes of Mannen (Møre and Romsdal county, southern Norway) and Gámanjunni-3 (Troms and Finnmark county, northern Norway) were classified as high-risk sites by the Norwegian Geological Survey (NGU). ...
    • Multi-elemental chemostratigraphy of Triassic mudstones in eastern Svalbard: implications for source rock formation in front of the World’s largest delta plain 

      Wesenlund, Fredrik; Grundvåg, Sten-Andreas; Engelschiøn, Victoria Sjøholt; Thieβen, Olaf; Pedersen, Jon Halvard (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-03)
      The Triassic Boreal Ocean was a shallow epicontinental basin and the sink of the World's largest delta plain known to date. Nutrient and freshwater supply from this delta have been regarded as important causes for high productivity and water mass stratification, forming Middle Triassic oil-prone source rocks. Recent studies attribute upwelling and a productivity-induced oxygen minimum zone as ...
    • Arctic Ocean glacial history 

      Jakobsson, Martin; Andreassen, Karin; Bjarnadóttir, Lilja Rún; Dove, Dayton; Dowdeswell, Julian A.; England, John H.; Funder, Svend; Hogan, Kelly; Ingólfsson, Ólafur; Jennings, Anne; Krog Larsen, Nikolaj; Kirchner, Nina; Landvik, Jon Y.; Mayer, Larry; Mikkelsen, Naja; Möller, Per; Niessen, Frank; Nilsson, Johan; O'Reagan, Matt; Polyak, Leonid; Nørgaard-Pedersen, Niels; Stein, Ruediger (Journal article; Tidsskriftartikkel; Peer reviewed, 2013-11-14)
      While there are numerous hypotheses concerning glacial–interglacial environmental and climatic regime shifts in the Arctic Ocean, a holistic view on the Northern Hemisphere's late Quaternary ice-sheet extent and their impact on ocean and sea-ice dynamics remains to be established. Here we aim to provide a step in this direction by presenting an overview of Arctic Ocean glacial history, based on the ...
    • Methane hydrate formation in Ulleung basin under conditions of variable salinity: reduced model and experiments 

      Peszynska, Malgorzata; Hong, Wei-Li; Torres, Marta E.; Kim, Ji-Hoon (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-06-13)
      In this paper, we present a reduced model of methane hydrate formation in variable salinity conditions, with details on the equilibrium phase behavior adapted to a case study from Ulleung Basin. The model simplifies the comprehensive model considered by Liu and Flemings using common assumptions on hydrostatic pressure, geothermal gradient, and phase incompressibility, as well as a simplified ...
    • A new methodology for quantifying bubble flow rates in deep water using splitbeam echosounders: Examples from the Arctic offshore NW-Svalbard 

      Veloso, M.; Greinert, Jens; Mienert, Jurgen; De Batist, M. (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-05-08)
      Quantifying marine methane fluxes of free gas (bubbles) from the seafloor into the water column is of importance for climate related studies, for example, in the Arctic, reliable methodologies are also of interest for studying man-made gas and oil leakage systems at hydrocarbon production sites. Hydroacoustic surveys with singlebeam and nowadays also multibeam systems have been proven to be a ...
    • High-temperature fracturing and subsequent grain-size-sensitive creep in lower crustal gabbros: Evidence for coseismic loading followed by creep during decaying stress in the lower crust 

      Okudaira, Takamoto; Jeřábek, Petr; Stunitz, Holger; Fusseis, Florian (Journal article; Tidsskriftartikkel; Peer reviewed, 2015)
      The mechanism of shear zone formation in lower crustal, relatively “dry” rocks is still poorly understood. We have studied the high-temperature deformation of the Hasvik gabbro (northern Norway) which commences by fracturing. The 10–20 μm wide fractures show little displacement. The fine-grained plagioclase and orthopyroxene in the fractures lack a crystallographic preferred orientation (CPO) or ...
    • Impact of Gas Saturation and Gas Column Height at the Base of the Gas Hydrate Stability Zone on Fracturing and Seepage at Vestnesa Ridge, West-Svalbard Margin 

      Ramachandran, Hariharan; Plaza-Faverola, Andreia; Daigle, Hugh (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-04-26)
      The Vestnesa Ridge, located off the west Svalbard margin, is a >60 km long ridge consisting of fine-grained sediments that host a deep-marine gas hydrate and associated seepage system. Geological and geophysical observations indicate the predominance of vertical fluid expulsion through fractures with pockmarks expressed on the seafloor along the entire ridge. However, despite the apparent evidence ...