Now showing items 720-739 of 989

    • Reconstructing the holocene. Benthic foraminifera as a proxy for the paleoceonography of the nordic seas 

      Baker, May Lizabeth (Master thesis; Mastergradsoppgave, 2017-08-01)
      The benthic foraminifera of two marine sediment cores were studied as a proxy for paleoenvironment reconstructions throughout the Late to Early Holocene. The two cores were sampled in different localities to allow a spatial comparison of changing environments in the Nordic Seas and sampled for benthic foraminiferal assemblages, grain size, IRD, sortable silts and benthic foraminifera isotopes. While ...
    • Reconstructing the retreat dynamics of the Bjørnøyrenna Ice Stream based on new 3D seismic data from the central Barents Sea 

      Piasecka, Emilia Daria; Winsborrow, Monica; Andreassen, Karin; Stokes, Chris R. (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-11-01)
      The stability of contemporary ice sheets is influenced by the discharge from ice streams - corridors of fast-flowing ice bounded by ice flowing an order of magnitude slower. Reconstructions of palaeo-ice stream dynamics contribute to our understanding of ice stream sensitivity to the ocean-climate system and can aid in the numerical modelling and prediction of future changes in contemporary ice ...
    • 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. ...
    • Reconstruction of Atlantic Water variability during the Holocene in the western Barents Sea 

      Groot, Diane; Sørensen, Steffen Aagaard; Husum, Katrine (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-01-10)
      The gravity core JM09-KA11-GC from 345m water depth on the western Barents Sea margin was investigated for down-core distribution patterns of benthic Foraminifera, stable isotopes, and sedimentological parameters in order to reconstruct the flow of Atlantic water during the Holocene. The core site is located below the Atlantic water masses flowing into the Arctic Ocean and close to the Arctic front. ...
    • Reconstruction of Holocene Paleoenvironment in Smeerenburgfjorden, northwest Svalbard based on benthic foraminifera and sedimentological investigations 

      Arnardóttir, Erna Ósk (Master thesis; Mastergradsoppgave, 2015-05-16)
      Two gravity cores JM06-024-GC3 and JM07-049-GC1 from Smeerenburgfjorden at the northwestern corner of Svalbard have been investigated for the distribution pattern of the benthic foraminiferal faunas. The oxygen and carbon isotope values in benthic foraminifera were analysed and together with other proxy data such as ice rafted debris (IRD), were used in order to reconstruct the paleoceanography and ...
    • Reconstruction of hydrographic changes in the southern Norwegian Sea during the past 135 kyr and the impact of different foraminiferal Mg/Ca cleaning protocols 

      Ezat, Mohamed; Rasmussen, Tine Lander; Groeneveld, Jeroen (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-08-20)
      The shallow subsurface hydrography in the southern Norwegian Sea during the past 135,000 years was investigated using parallel measurements of Mg/Ca and δ18O in shells of the planktic foraminiferal species Neogloboquadrina pachyderma. Two cleaning methods were applied prior to Mg/Ca analysis, “Mg cleaning” and “full cleaning” methods. Different results were obtained, which are most likely due to a ...
    • Reconstruction of ice sheet retreat after the Last Glacial maximum in Storfjorden, southern Svalbard 

      Nielsen, Tove; Rasmussen, Tine Lander (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-15)
      Storfjorden is a large north-south trending sound located in the southern part of Svalbard in the northwestern Barents Sea. Presently, several glaciers drain into the northern and western part of Storfjorden. Our study area covers the southern part of the sound, which is divided by a north-south striking basement ridge (the ‘Mid-ridge’) into a narrow western trough (‘Little-Storfjorden’) and a broader ...
    • Reconstruction of ice stream retreat and palaeoceanographic development during the deglaciation and Holocene in the Storfjorden Trough, Svalbard. Based on geophysical data, benthic foraminiferal and sedimentological records 

      Lockwood, Christine Joanne (Master thesis; Mastergradsoppgave, 2016-05-15)
      Here we investigate the retreat of a palaeo-ice stream and the subsequent palaeoceanographic development in the eastern Storfjorden Trough during the deglaciation and Holocene. The results are based on multibeam bathymetric and acoustic sub-bottom data, and a multiproxy analysis of a 14C dated sediment core (including benthic foraminifera, δ13C, δ18O and sedimentology). The ice stream experienced a ...
    • Reconstruction of late Holocene paleoenvironment in Kongsfjorden, West Spitsbergen. Based on analysis of benthic foraminifera 

      Danielsen, Kim-André (Master thesis; Mastergradsoppgave, 2017-05-15)
      The benthic foraminiferal fauna of two marine sediment records from the Kongsfjorden Trough and the inner part of Kongsfjorden were analyzed to reconstruct the paleoenvironmental development throughout the last ~ 2000 years. A generally cold period is evident in both records, lasting from ~ 700 to 1400 CE at the Kongsfjorden Trough and from ~ 350 to 1200 CE in the inner part of Kongsfjorden, with ...
    • Reconstruction of the bottom current strength of overflow water through the Faeroe-Shetland Channel in relation to climate change during the last 135,000 years 

      Solheim, Martin (Master thesis; Mastergradsoppgave, 2018-05-15)
      The focus of this thesis was to reconstruct the bottom current strength around the Faeroe Islands and relate it to the climate variability over the past 35,000 - 135,000 years and the Holocene, using the piston core, JM11-FI-19PC, from the North-eastern shelf of the Faeroe Islands. The core location is ideal for measuring the overflow from the Nordic Seas, as it is strategically placed on top of the ...
    • Reconstruction of the Kråknes landslide event, Alta 

      Pettersen, Stina Mari (Master thesis; Mastergradsoppgave, 2021-05-15)
      On June 3rd, 2020 a major quick clay landslide occurred at Kråknes in Alta municipality, Northern Norway. The landslide event destroyed eight buildings and was estimated to be 650 meters wide and 40 meters high. Two days later, another landslide occurred, this time causing the old E6 road above the previous landslide area to slip out towards the sea. People lost cabins and other valuable possessions, ...
    • Reconstruction of the paleocenaography west of Lofoten during the Last Glacial Maximum 

      Mathisen, Marthe Marie (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 ...
    • Reconstruction of the Virtual Geomagnetic Pole (VGP) path at high latitude for the last 22 kyr: The role of radial field flux patches as VGP attractor 

      Caricchi, Chiara; Campuzano, Saioa A.; Sagnotti, Leonardo; Macri, Patrizia; Lucchi, Renata Giulia (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-24)
      Reconstruction of geomagnetic field changes has a strong potential to complement geodynamo modeling and improve the understanding of Earth's core dynamics. Recent works based on geomagnetic measurements pointed out that over the last two decades the position of the north magnetic pole has been largely determined by the influence of two competing flux lobes under Canada and Siberia. In order to ...
    • Reconstructions of paleoceanography and ice retreat based on benthic foraminifera, stable isotopes and sedimentological investigations from the northwestern Barents Sea south of Nordaustlandet, Svalbard 

      Eilertsen, Vårin Trælvik (Master thesis; Mastergradsoppgave, 2016-07-12)
      One gracity core NP05–11–49GC was retrieved from a 320 m water depth in the central part of Erik Eriksen Strait, south of Nordaustlandet, northwestern Barents Sea. The core was investigated for benthic foraminiferal distribution patterns, stable isotopes and sedimentological parameters in order to reconstruct the Late Weichselian deglaciation and Holocene paleoenvironment and paleoceanography of the ...
    • Redox fluctuations, trace metal enrichment and phosphogenesis in the ~2.0 Ga Zaonega Formation 

      Kipp, Michael A.; Lepland, Aivo; Buick, Roger (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-24)
      The ~2.0 Ga Zaonega Formation (ZF) holds one of the oldest phosphorites in the geologic record, reaching >15% P<sub>2</sub>O<sub>5</sub>. Understanding the depositional conditions that enabled sedimentary phosphorus enrichment in this unit will thus help us to interpret the significance of the temporal distribution of phosphorites in Earth’s early history. Here we use an array of major and trace ...
    • Redox state of the Dharwar craton root as inferred from eclogite and peridotite sourced mantle cargo, with implications for kimberlite and lamproite magma formation 

      Shaikh, Azhar M.; Bussweiler, Yannick; Viljoen, Fanus; Bolhar, Robert; Ravi, S.; Hezel, Dominik C.; Ueckermann, Henriëtte; Tappe, Sebastian (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-11-16)
      Despite over 400 occurrences of kimberlites and related rocks in India, mantle-derived xenoliths are known only from a few occurrences. This paucity of mantle-derived xenoliths in Indian kimberlites has hampered investigations of the subcontinental lithospheric mantle (SCLM). Using a valuable selection of the rare xenolith inventory, we here report Fe<sup>3+</sup>/ΣFe measurements for garnets using ...
    • Redox-dependent niche differentiation provides evidence for multiple bacterial sources of glycerol tetraether lipids in lakes 

      Weber, Yuki; Sinninghe Damsté, Jaap S.; Zopfi, Jakob; De Jonge, Cindy; Gilli, Adrian; Schubert, Carsten J.; Lepori, Fabio; Lehmann, Moritz F.; Niemann, Helge (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-10-23)
      Terrestrial paleoclimate archives such as lake sediments are essential for our understanding of the continental climate system and for the modeling of future climate scenarios. However, quantitative proxies for the determination of paleotemperatures are sparse. The relative abundances of certain bacterial lipids, i.e., branched glycerol dialkyl glycerol tetraethers (brGDGTs), respond to changes in ...
    • Reduced Arctic sea ice extent during the mid-Pliocene Warm Period concurrent with increased Atlantic-climate regime 

      Rahaman, Waliur; Smik, Lukas; Köseoğlu, Denizcan; Lathika, N.; Tarique, Mohd; Thamban, Meloth; Haywood, Alan; Belt, Simon T.; Knies, Jochen (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-01)
      Quantifying the contribution of poleward oceanic heat transport to the Arctic Ocean is important for making future sea ice and climate predictions. To highlight its potential importance in a warmer world, we present a new record of water-mass exchange between the Atlantic and the Arctic Oceans using the authigenic neodymium isotopic composition of marine sediments from the Fram Strait during the ...
    • Reduced methane seepage from Arctic sediments during cold bottom-water conditions 

      Ferré, Benedicte; Jansson, Pär; Moser, Manuel; Serov, Pavel; Portnov, Aleksei D; Graves, Carolyn; Panieri, Giuliana; Gründger, Friederike; Berndt, Christian; Lehmann, Moritz F.; Niemann, Helge (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-13)
      Large amounts of methane are trapped within gas hydrate in subseabed sediments in the Arctic Ocean, and bottom-water warming may induce the release of methane from the seafloor. Yet the effect of seasonal temperature variations on methane seepage activity remains unknown as surveys in Arctic seas are conducted mainly in summer. Here we compare the activity of cold seeps along the gas hydrate stability ...
    • Reduced Numerical Model for Methane Hydrate Formation under Conditions of Variable Salinity. Time-Stepping Variants and Sensitivity 

      Peszynska, M.; Medina, F.P.; Hong, Wei-Li; Torres, M. (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-12-24)
      In this paper, we consider a reduced computational model of methane hydrate formation in variable salinity conditions, and give details on the discretization and phase equilibria implementation. We describe three time-stepping variants: Implicit, Semi-implicit, and Sequential, and we compare the accuracy and efficiency of these variants depending on the spatial and temporal discretization parameters. ...