Viser treff 118-137 av 711

    • 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 ...
    • Deformation mechanisms accommodating progressive simple shear thrusting of quartzite and metacarbonate in the southwestern Espinhaço Range, Brazil 

      Taufner, Rhander; Lagoeiro, Leonardo E.; Cavalcante, Carolina; Barbosa, Paola; Silveira, Camila Santos (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-09)
      The accommodation of low-temperature ductile deformation in foreland fold-and-thrust belts is often described in terms of outcrop-based geometric analysis, but microtextural observations are also important, as they relate stress, strain, fluids and temperature and thus the rheology in the peripheral part of the orogen. Such microtextural observations are lacking from the foreland part of the Araçuaí ...
    • Deglacial dynamics of the Vestfjorden - Trænadjupet palaeo-ice stream, northern Norway 

      Laberg, Jan Sverre; Eilertsen, Raymond S; Salomonsen, Gaute R. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-05-18)
      Few well‐dated records of the deglacial dynamics of the large palaeo‐ice streams of the major Northern Hemisphere ice sheets are presently available, a prerequisite for an improved understanding of the ice‐sheet response to the climate warming of this period. Here we present a transect of gravity‐core samples through Trænadjupet and Vestfjorden, northern Norway, the location of the Trænadjupet – ...
    • Deglacial–Holocene Svalbard paleoceanography and evidence of Melt Water Pulse 1B 

      Tian, Skye Y.; Yasuhara, Moriaki; Hong, Y.; Huang, H.-H.; Iwatani, H.; Chiu, W.-T. R.; Mamo, Bryoni; Okahashi, Hisayo; Rasmussen, Tine Lander (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-09)
      Better understanding of deglacial meltwater pulses (MWPs) is imperative for future predictions of human-induced warming and abrupt sea-level change because of their potential for catastrophic damage. However, our knowledge of the second largest meltwater pulse MWP-1B that occurred shortly after the start of the Holocene interglacial remains very limited. Here, we studied fossil ostracods as ...
    • Deglaciation of the central Barents Sea 

      Bjarnadóttir, Lilja Rún; Winsborrow, Monica C. M.; Andreassen, Karin (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-05-15)
      The marine-based Barents Sea Ice Sheet covered the polar continental shelf north of Norway and western Russia during the Last Glacial Maximum. Initial ice sheet retreat along the western margin is well established, while the retreat pattern in the interior parts of the ice sheet remains poorly known. Here we present new geological data from the central Barents Sea. The results are based on analysis ...
    • Deglaciation of the Eurasian ice sheet complex 

      Patton, Henry; Hubbard, Alun Lloyd; Andreassen, Karin; Auriac, Amandine; Whitehouse, Pippa L.; Stroeven, Arjen P.; Shackleton, Calvin; Winsborrow, Monica; Heyman, Jakob; Hall, Adrian M. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-14)
      The Eurasian ice sheet complex (EISC) was the third largest ice mass during the Last Glacial Maximum with a span of over 4500 km and responsible for around 20 m of eustatic sea-level lowering. Whilst recent terrestrial and marine empirical insights have improved understanding of the chronology, pattern and rates of retreat of this vast ice sheet, a concerted attempt to model the deglaciation of the ...
    • Depositional environment, ichnological features and oxygenation of Permian to earliest Triassic marine sediments in central Spitsbergen, Svalbard 

      Uchman, Alfred; Hanken, Nils-Martin; Nielsen, Jesper Kresten; Grundvåg, Sten-Andreas; Piasecki, Stefan (Journal article; Tidsskriftartikkel; Peer reviewed, 2016)
      Late Early Permian–lowermost Triassic carbonate, siliceous (spiculites) and clastic marine sediments in the Marmierfjellet area (Isfjorden, central Spitsbergen) contain a relatively diverse and abundant trace fossil assemblage providing important information about the depositional processes. The Vøringen Member (Late Artinskian–Kungurian) of the Kapp Starostin Formation (Late Artinskian–? Changhsingian) ...
    • Depositional environments and source rock potential of some Upper Palaeozoic (Devonian) coals on Bjørnøya, Western Barents shelf 

      Janocha, Julian; Wesenlund, Fredrik; Thießen, Olaf; Grundvåg, Sten-Andreas; Koehl, Jean-Baptiste Philippe; Johannessen, Erik P. (Journal article; Tidsskriftartikkel; Peer reviewed, 2024-02-27)
      Upper Palaeozoic strata are potential sources for hydrocarbon plays on the Norwegian Barents Shelf. The island of Bjørnøya (Bear Island) is located on the western margin of the Barents Shelf and represents an exposed part of the Stappen High, which makes it an excellent location to investigate the source rock potential of this succession. Here, we investigate the organic geochemical composition and ...
    • Depositional processes on the distal Scoresby Trough Mouth Fan (ODP Site 987): Implications for the Pleistocene evolution of the Scoresby Sund Sector of the Greenland Ice Sheet 

      Laberg, Jan Sverre; Rydningen, Tom Arne; Forwick, Matthias; Husum, Katrine (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-28)
      The investigation of trough mouth fans (TMFs), important paleoclimatic archives on mid- and high-latitude continental margins, has so far mainly been based on the integration of various types of acoustic data supplemented with short sediments cores. In consequence, sedimentological and chronological data about parts of TMFs deposited prior to the Last Glacial Maximum remains sparse. Here, we re-evaluate ...
    • Derivation of High Spatial Resolution Albedo from UAV Digital Imagery: Application over the Greenland Ice Sheet 

      Ryan, Jonathan C.; Hubbard, Alun Lloyd; Box, Jason E.; Brough, Stephen; Cameron, Karen; Cook, Joseph M.; Cooper, Matthew; Doyle, Samuel H.; Edwards, Arwyn; Holt, Tom; Irvine-Fynn, Tristram; Jones, Christine; Pitcher, Lincoln H.; Rennermalm, Åsa K.; Smith, Laurence C.; Stibal, Marek; Snooke, Neal (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-05-23)
      Measurements of albedo are a prerequisite for modeling surface melt across the Earth’s cryosphere, yet available satellite products are limited in spatial and/or temporal resolution. Here, we present a practical methodology to obtain centimeter resolution albedo products with accuracies of ±5% using consumer-grade digital camera and unmanned aerial vehicle (UAV) technologies. Our method comprises ...
    • Detection of gas hydrates in faults using azimuthal seismic velocity analysis,Vestnesa Ridge, W-Svalbard Margin 

      Singhroha, Sunny; Bünz, Stefan; Plaza Faverola, Andreia Aletia; Chand, Shyam (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-24)
      Joint analysis of electrical resistivity and seismic velocity data is primarily used todetect the presence of gas hydrate-filled faultsand fractures. In this study, we present a novel approach to inferthe occurrence of structurally-controlled gas hydrateaccumulations using azimuthal seismic velocity analysis. We perform thisanalysis using ocean-bottom seismic (OBS) data at two sites on Vestnesa ...
    • Detectionof gas hydrates infaults using azimuthal seismic velocity analysis,Vestnesa Ridge, W-Svalbard Margin 

      Singhroha, Sunny; Bünz, Stefan; Plaza-Faverola, Andreia; Chand, Shyam (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-24)
      Joint analysis of electrical resistivity and seismic velocity data is primarily used to detect the presence of gas hydrate‐filled faults and fractures. In this study, we present a novel approach to infer the occurrence of structurally‐controlled gas hydrate accumulations using azimuthal seismic velocity analysis. We perform this analysis using ocean‐bottom seismic (OBS) data at two sites on Vestnesa ...
    • Development of the NORSAR Network over the Last 50 Yr 

      Schweitzer, Johannes; Köhler, Andreas; Christensen, Jon Magnus (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-27)
      This contribution describes the development of Norwegian Seismic Array (NORSAR), from its origin 50 yr ago as a project for installing a single seismic array in southern Norway to a seismological research institute operating a network of six arrays and 14 three‐component stations located in Norway and Antarctica. In addition, we document the different instrumentations from narrowband, mostly ...
    • Development, productivity, and seasonality of living planktonic foraminiferal faunas and Limacina helicina in an area of intense methane seepage in the Barents Sea 

      Ofstad, Siri; Meilland, Julie; Zamelczyk, Katarzyna; Chierici, Melissa; Fransson, Agneta; Gründger, Friederike; Rasmussen, Tine Lander (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-09)
      Although the plankton communities in the Barents Sea have been intensely studied for decades, little is known about the living planktonic foraminiferal (LPF) and pteropod faunas, especially those found at methane seep sites. Along a repeated transect in the “crater area” (northern Barents Sea, 74.9°N, 27.7°E) in spring and summer 2016 the flux of LPF and of the pteropod species <i>Limacina helicina</i> ...
    • Devonian core complex exhumation and Cenozoic decollements as alternatives to the Ellesmerian Orogeny 

      Koehl, Jean-Baptiste P. (Conference object; Konferansebidrag, 2018-10)
      The Ellesmerian Orogeny (Piepjohn et al., 2000) is a short-lived contractional–transpressional event that occurred in the Late Devonian–Mississippian, i.e., after Devonian collapse of the Caledonides and prior to Carboniferous rifting. Thus far, this episode of contraction–transpression was required to explain the presence of undeformed Carboniferous–Permian sedimentary rocks on top of folded ...
    • Diagenetic alteration of benthic foraminifera from a methane seep site on Vestnesa Ridge (NW Svalbard) 

      Schneider, Andrea; Cremiere, Antoine; Panieri, Giuliana; Lepland, Aivo; Knies, Jochen (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-03-08)
      Anomalously low δ<sup>13</sup>C values in foraminiferal calcite tests are due to diagenetic alteration in methane seep sites. Our study applies diagenetically altered fossil benthic foraminiferal tests as geochemical tracers in reconstructing natural past methane seepage episodes at Vestnesa Ridge offshore NW Svalbard. We combine examinations of the test wall microstructure, mineralogical and stable ...
    • Diel and seasonal methane dynamics in the shallow and turbulent Wadden Sea 

      de Groot, Tim René; Mol, Anne Margriet; Mesdag, Katherine; Ramond, Pierre; Ndhlovu, Rachel; Engelmann, Julia Catherine; Röckmann, Thomas; Niemann, Helge (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-25)
      The Wadden Sea is a coastal system along the fringe of the land–sea borders of Denmark, Germany and the Netherlands. The Wadden Sea is extremely productive and influenced by strong variations in physical and biological forcing factors that act on timescales of hours to seasons. Productive coastal seas are known to dominate the ocean's methane emission to the atmosphere, but knowledge of controls and ...
    • Digitising Svalbard’s geology: the Festningen digital outcrop model 

      Senger, Kim; Betlem, Peter; Birchall, Thomas; Gonzaga Jr., Luis; Grundvåg, Sten-Andreas; Horota, Rafael Kenji; Laake, Andreas; Kuckero, Lilith; Mørk, Atle; Planke, Sverre; Rodes, Nil; Smyrak-Sikora, Aleksandra (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-10)
      The renowned Festningen section in the outer part of Isfjorden, western Spitsbergen, offers a c. 7 km-long nearly continuous stratigraphic section of Lower Carboniferous to Cenozoic strata, spanning nearly 300 million years of geological history. Tectonic deformation associated with the Paleogene West-Spitsbergen-Fold-and-Thrust belt tilted the strata to near-vertical, allowing easy access to the ...
    • Dinocyst stratigraphy of the Valanginian to Aptian succession (the Rurikfjellet and Helvetiafjellet formations) from Spitsbergen, Norway 

      Śliwińska, Kasia; Jelby, Mads; Grundvåg, Sten-Andreas; Nøhr-Hansen, N.; Alsen, P; Olaussen, Snorre (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-11)
      In order to improve the understanding of how the high northern latitudes responded to the escalating warming which led to the middle Cretaceous super greenhouse climate, more temperature proxy records from the High Arctic are needed. One of the current obstacles in obtaining such records is poor age control on the Lower Cretaceous strata in the Boreal region. Here, we provide a biostratigraphic ...
    • The dinoflagellate cyst genera Achomosphaera Evitt 1963 and Spiniferites Mantell 1850 in Pliocene to modern sediments: a summary of round table discussions 

      Mertens, Kenneth Neil; Van Nieuwenhove, Nicolas; Gurdebeke, Pieter R; Aydin, Hilal; Bogus, Kara; Bringué, Manuel; Dale, Barrie; De Schepper, Stijn; de Vernal, Anne; Ellegaard, Marianne; Grothe, Arjen; Gu, Haifeng; Head, Martin J.; Heikillä, Maija; Limoges, Audrey; Londeix, Laurent; Louwye, Stephen; Marret, Fabienne; Masure, Edwige; Matsuoka, Kazumi; Mudie, Peta J.; Penaud, Aurélie; Pospelova, Vera; Price, Andrea Michelle; Ribeiro, Sofia; Rochon, André; Sangiorgi, Francesca; Schreck, Michael; Torres, Vladimir; Uzar, Serdar; Versteegh, Gerard J M; Warny, Sophie; Zonneveld, Karin (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-14)
      We present a summary of two round-table discussions held during two subsequent workshops in Montreal (Canada) on 16 April 2014 and Ostend (Belgium) on 8 July 2015. Five species of the genus <i>Achomosphaera</i> Evitt 1963 and 33 of the genus <i>Spiniferites</i> Mantell 1850 emend. Sarjeant 1970 occuring in Pliocene to modern sediments are listed and briefly described along with remarks made by ...