Viser treff 261-280 av 729

    • Provenance, depositional setting and diagenesis as keys to reservoir quality of the Lower Cretaceous in the SW Barents Sea 

      Arlebrand, Berit Angelica; Augustsson, Carita; Escalona, Alejandro; Grundvåg, Sten-Andreas (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-06)
      This study examines the role of the depositional environment for the final reservoir quality in four Lower Cretaceous sandstone reservoirs in the southwestern Barents Sea by linking facies to the distribution of primary textures, composition, and diagenetic alteration. Facies analysis reveals slope-to-basin-floor, distal shallow-marine, and deltaic depositional environments. The slope-to-basin-floor ...
    • Luminescence dating of holocene siliciclastic sediments in eastern Dahomey Basin, southwestern Nigeria 

      Fakolade, Richard O.; Ikhane, Philip R.; Zhao, Qiuyue; Hao, Qingzhen; Alexanderson, Helena; Guo, Zhengtang (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-02)
      Several attempts at reconstructing geological settings and palaeoclimatic changes of the siliciclastic deposits of the Dahomey Basin, SW Nigeria, using relative age dating and correlation methods, have resulted in serious discrepancies on the ages. Therefore, a chronology framework established by an absolute age dating method is requisite to constrain the geological interpretation. This research ...
    • Palaeoproterozoic foreland fold-thrust belt structures and lateral faults in the West Troms Basement Complex, northern Norway, and their relation to inverted metasedimentary sequences 

      Paulsen, Hanne-Kristin; Bergh, Steffen G; Palinkas, Sabina Strmic; Karlsen, Siri; Kolsum, Sofie; Rønningen, Ida Ulvik; Armitage, Paul E.B.; Nasuti, Aziz (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-15)
      Palaeoproterozoic fold-thrust belt structures and steep, lateral shear zones characterize the foreland deformation of Neoarchaean basement tonalites in Vanna, West Troms Basement Complex, northern Norway. Low-grade par-autochthonous and allochthonous cover units (2.4–2.2. Ga) with sandstones and calcareous metapelites exist in separate areas of the foreland. They were formed as intracontinental rift- ...
    • Historical contingency impacts on community assembly and ecosystem function in chemosynthetic marine ecosystems 

      Kalenitchenko, Dimitri; Peru, Erwan; Galand, Pierre E. (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 

      Ezat, Mohamed; Rasmussen, Tine Lander; Hain, Mathis P.; Greaves, Mervyn; Rae, James W.B.; Zamelczyk, Katarzyna; Marchitto, Thomas M.; Szidat, Sönke; Skinner, Luke C. (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 ...
    • 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 

      Alexandropoulou, Nikolitsa; Winsborrow, Monica; Andreassen, Karin; Plaza-Faverola, Andreia; Dessandier, Pierre-Antoine; Mattingsdal, Rune; Baeten, Nicole; Knies, Jochen (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 

      Pieńkowski, Anna J.; Husum, Katrine; Belt, Simon T.; Ninnemann, Ulysses S; Köseoğlu, Denizcan; Divine, Dmitry V.; Smik, Lukas; Knies, Jochen; Hogan, Kelly; Noormets, Riko (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 ...
    • Shell density of planktonic foraminifera and pteropod species Limacina helicina in the Barents Sea: Relation to ontogeny and water chemistry 

      Ofstad, Siri; Zamelczyk, Katarzyna; Kimoto, Katsunori; Chierici, Melissa; Fransson, Agneta; Rasmussen, Tine Lander (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 

      Nègre, Lucille; Stunitz, Holger; Raimbourg, Hugues; Lee, Amicia; Précigout, Jacques; Pongrac, Petar; Jeřábek, Petr (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 

      Cearreta, Alejandro; Irabien, María Jesús; Arozamena, José E. Gómez; El Bani Altuna, Naima; Goffard, Aintzane; García-Artola, Ane (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 ...
    • Storage and export of microbial biomass across the western Greenland Ice Sheet 

      Irvine-Fynn, Tristram D.L.; Edwards, A.; Stevens, I.T.; Mitchell, A.C.; Bunting, P.; Box, J.E.; Cameron, K.A.; Cook, J.M.; Naegeli, K.; Rassner, S.M.E.; Ryan, J.C.; Stibal, M.; Williamson, C.J.; Hubbard, Alun Lloyd (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 

      Romeyn, Rowan; Hanssen, Alfred; Ruud, Bent Ole; Johansen, Tor Arne (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 

      Argentino, Claudio; Waghorn, Kate Alyse; Vadakkepuliyambatta, Sunil; Polteau, Stephane; Bünz, Stefan; Panieri, Giuliana (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 

      Gründger, Friederike; Probandt, David; Knittel, Katrin; Carrier, Vincent; Kalenitchenko, Dimitri; Silyakova, Anna; Serov, Pavel; Ferré, Benedicte; Svenning, Mette Marianne; Niemann, Helge (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 ...
    • Large subglacial source of mercury from the southwestern margin of the Greenland Ice Sheet 

      Hawkings, Jon R.; Linhoff, Benjamin S.; Wadham, Jemma L.; Stibal, Marek; Lamborg, Carl H.; Carling, Gregory T.; Lamarche-Gagnon, Guillaume; Kohler, Tyler J.; Ward, Rachael; Hendry, Katharine R.; Falteisek, Lukáš; Kellerman, Anne M.; Cameron, Karen A.; Hatton, Jade E.; Tingey, Sarah; Holt, Amy D.; Vinšová, Petra; Hofer, Stefan; Bulínová, Marie; Větrovský, Tomáš; Meire, Lorenz; Spencer, Robert G. M. (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 

      Argentino, Claudio; Lugli, Federico; Cipriani, Anna; Panieri, Giuliana (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 

      Mun, Yulia; Palinkas, Sabina Strmic; Kullerud, Kåre (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 ...
    • Planktic foraminiferal and pteropod contributions to carbon dynamics in the Arctic Ocean (north Svalbard margin) 

      Anglada-Ortiz, Griselda; Zamelczyk, Katarzyna; Meilland, Julie; Ziveri, Patrizia; Chierici, Melissa; Fransson, Agneta; Rasmussen, Tine Lander (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-09)
      Planktic foraminifera and shelled pteropods are some of the major producers of calcium carbonate (CaCO<sub>3</sub>) in the ocean. Their calcitic (foraminifera) and aragonitic (pteropods) shells are particularly sensitive to changes in the carbonate chemistry and play an important role for the inorganic and organic carbon pump of the ocean. Here, we have studied the abundance distribution of planktic ...
    • The fate of plastic in the ocean environment – a minireview 

      Wayman, Chloe; Niemann, Helge (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-14)
      The presence of plastics in the marine environment poses a threat to ocean life and has received much scientific and public attention in recent years. Plastics were introduced to the market in the 1950s and since then, global production figures and ocean plastic littering have increased exponentially. Of the 359 million tonnes (Mt) produced in 2018, an estimated 14.5 Mt has entered the ocean. In ...
    • Deformation Behavior and Inferred Seismic Properties of Tonalitic Migmatites at the Time of Pre‐melting, Partial Melting, and Post‐Solidification 

      Shao, Yilun; Piazolo, Sandra; Liu, Yongjiang; Lee, Amicia; Jin, Wei; Li, Weimin; Liang, Chenyue; Wen, Quanbo (Journal article; Tidsskriftartikkel, 2021-01-21)
      As seismic data from the lower crust becomes more readily available, it is important to link seismic properties to the ongoing processes within lower crustal evolution. This includes high temperature, pre‐ and post‐migmatization solid state deformation as well as melt‐present deformation. We selected two tonalitic migmatites with variable former melt content (one metatexite and one diatexite) from ...