Viser treff 181-200 av 708

    • Event recognition in marine seismological data using Random Forest machine learning classifier 

      Domel, Przemyslaw; Hibert, Clément; Schlindwein, Vera; Plaza-Faverola, Andreia (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-16)
      Automatic detection of seismic events in ocean bottom seismometer (OBS) data is difficult due to elevated levels of noise compared to the recordings from land. Popular deep-learning approaches that work well with earthquakes recorded on land perform poorly in a marine setting. Their adaptation to OBS data requires catalogues containing hundreds of thousands of labelled event examples that currently ...
    • Evidence for ice-free summers in the late Miocene central Arctic Ocean 

      Stein, Ruediger; Fahl, Kirsten; Schreck, Michael; Knorr, Gregor; Niessen, Frank; Forwick, Matthias; Gebhardt, Catalina; Jensen, Laura; Kaminski, Michael; Kopf, Achim; Matthiessen, Jens; Jokat, Wilfried; Lohmann, Gerrit (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-04-04)
      Although the permanently to seasonally ice-covered Arctic Ocean is a unique and sensitive component in the Earth’s climate system, the knowledge of its long-term climate history remains very limited due to the restricted number of pre-Quaternary sedimentary records. During Polarstern Expedition PS87/2014, we discovered multiple submarine landslides along Lomonosov Ridge. Removal of younger ...
    • Evidence for influx of Atlantic water masses to the Labrador Sea during the Last Glacial Maximum 

      Seidenkrantz, Marit-Solveig; Kuijpers, Antoon; Sørensen, Steffen Aagaard; Lindgreen, Holger; Olsen, Jesper; Pearce, Christof (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-03-21)
      The Last Glacial Maximum (LGM, 23–19,000 year BP) designates a period of extensive glacial extent and very cold conditions on the Northern Hemisphere. The strength of ocean circulation during this period has been highly debated. Based on investigations of two marine sediment cores from the Davis Strait (1033 m water depth) and the northern Labrador Sea (2381 m), we demonstrate a significant influx ...
    • Evidence of Arctic methane emissions across the mid-Pleistocene 

      Panieri, Giuliana; Knies, Jochen Manfred; Vadakkepuliyambatta, Sunil; Lee, Amicia; Schubert, Carsten J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-08)
      During the Pleistocene, Earth’s climate changed dramatically. The mid-Pleistocene transition (MPT; ~1.3–0.7 million years (Ma)) featured an important ice volume increase at both poles. The evolution of large Arctic ice sheets caused the sequestration of methane as free gas and hydrates in subseabed sediments. Ice volume changes, associated with variable pressures and temperatures, perturbed those ...
    • Evidence of hyperpycnally fed turbidites in a basin floor setting, Eocene of Spitsbergen, Arctic Norway 

      Grundvåg, Sten-Andreas; Helland-Hansen, William (Conference object; Konferansebidrag, 2018)
      The Eocene of Spitsbergen, Svalbard, has received considerable attention in the literature because of its spectacular seismic-scale clinoforms exposed along many fiords and valleys. Previous investigations particularly focused on the slope segment of the clinoforms and demonstrated how sustained-type, hyperpycnal flows deriving from shelf-edge deltas played a major role in bringing sand onto the ...
    • Evidence of Isotopic Fractionation During Vapor Exchange Between the Atmosphere and the Snow Surface in Greenland 

      Madsen, M.V.; Steen‐Larsen, H.C.; Hörhold, M.; Box, J.; Berben, Sarah Miche Patricia; Capron, E.; Faber, Anne-Katrine; Hubbard, Alun Lloyd; Jensen, Mari Fjalstad; Jones, T.R.; Kipfstuhl, S.; Koldtoft, I.; Pillar, H.R.; Vaughn, B.H.; Vladimirova, D.; Dahl‐Jensen, D. (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 ...
    • Evidences of accelerating the increase in the concentration of methane in the atmosphere after 2014: satellite data for the Arctic 

      Yurganov, L. N.; Leifer, Ira; Vadakkepuliyambatta, Sunil (Journal article; Tidsskriftartikkel; Peer reviewed, 2017)
      Проанализированы результаты спутникового зондирования с помощью европейского орбитального интерферометра IASI/MetOP-A и алгоритма обработки данных, разработанного в NOAA. Спутниковые измерения для умеренных и высоких широт Северного полушария дают рост скорости концентрации метана от 4–9 ppbv/год (частей на миллиард по объему) в 2010–2013 гг. до 12–17 ppbv/год в 2015–2016 гг. Глобальные оценки на ...
    • Evolución ambiental de los estuarios del Geoparque de la costa Vasca durante el Holoceno y el Antropoceno 

      Cearreta, A.; Irabien, M.J.; Gómez Arozamena, J.; El Bani Altuna, Naima; Goffard, A.; Fernández Martín-Consuegra, A.; Hilario, A. (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 ...
    • Evolution and temporal constraints of a multiphase postglacial rock slope failure 

      Vick, Louise Mary; Mikkelsen, Martin; Corner, Geoffrey; Kjellman, Sofia Elisabeth; Trønnes, Leif; Hormes, Anne; Allaart, Lis; Bergh, Steffen G (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-05)
      Large rock slope failures are temporal processes which act to modify the landscape after glacial retreat. The slope failure process often shows a lag time of thousands of years after deglaciation, with multiple failure events possible. While global datasets constrain this lag time from extensive mapping and dating of paraglacial rock avalanches, the timeline is poorly refined in northern Norway. We ...
    • Evolution in H2O contents during deformation of polycrystalline quartz: An experimental study 

      Palazzin, Giulia; Raimbourg, Hugues; Stunitz, Holger; Heilbronner, Renée; Neufeld, Kai; Précigout, Jacques (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06-15)
      Shear experiments were performed in a Griggs-type apparatus at 800 °C and 1.5 GPa, at a strain rate of 2.1 × 10<sup>−5</sup>s<sup>−1</sup> using different starting materials: (i) Powder (grain size 6–10 μm) of dry Brazil quartz with 0.15 wt% added H<sub>2</sub>O, (ii) “dry” Brazil quartz porphyroclasts (grain size ∼100–200 μm), devoid of fluid inclusions embedded in the same fine grained powder, and ...
    • Evolution of a high-latitude sediment drift inside a glacially-carved trough based on high-resolution seismic stratigraphy (Kveithola, NW Barents Sea) 

      Rebesco, Michele; Özmaral, Asli; Urgeles, Roger; Accettella, Daniela; Lucchi, Renata G.; Rüther, Denise Christina; Winsborrow, Monica; Llopart, Jaume; Caburlotto, Andrea; Lantzsch, Hendrik; Hanebuth, Till J.J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-09-01)
      Kveithola is a glacially-carved, E-W trending trough located in the NW Barents Sea, an epicontinental shelf sea of the Arctic Ocean located off northern Norway and Russia. A set of confined sediment drifts (the “Kveithola Drift”) is located in the inner part of the trough. In general, drift deposits are commonly characterized by high lateral continuity, restricted occurrence of hiatuses and relatively ...
    • Evolution of a shear zone before, during and after melting 

      Lee, Amicia; Lloyd, Geoffrey E.; Torvela, Taija; Walker, Andrew M. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-03)
      Partial melt in the deforming mid- or lower continental crust causes a strength decrease and drives formation of lithological heterogeneities. However, mechanisms of formation of syn-melt deformation zones and strain partitioning in partially molten rock remain poorly understood. We use field and microstructural observations to unravel the evolution of a partial melt shear zone, Seiland Igneous ...
    • Evolution of contourite drifts in regions of slope failures at eastern Fram Strait 

      Osti, Giacomo; Waghorn, Kate Alyse; Waage, Malin; Plaza-Faverola, Andreia; Ferré, Benedicte (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-15)
      Geotechnical characteristics of contouritic deposition often lead to preconditioning slope instabilities and failures along glaciated and formerly glaciated continental margins.<br> However, internal depositional geometry is also an important factor in triggering instabilities. This work highlights the importance of the tectonic and oceanographic evolution of the Northwestern (NW) Svalbard margin ...
    • Evolution of metal-bearing fluids at the Nussir and Ulveryggen sediment-hosted Cu deposits, Repparfjord Tectonic Window, northern Norway 

      Mun, Yulia; Strmic Palinkas, Sabina; Kullerud, Kåre; Nilsen, Kjell S.; Neufeld, Kai; Bekker, Andrey (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-13)
      The Palaeoproterozoic greenstone belts of Fennoscandia are metamorphosed and deformed volcanic and sedimentary rocks that formed in basins with a high base-metal ore potential. One of these, the Repparfjord Tectonic Window (RTW), is exposed in the Caledonides of northern Norway and contains several sediment-hosted Cu deposits including Nussir and Ulveryggen. The RTW is composed of mafic metavolcanic ...
    • 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 ...
    • 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 ultrapotassic volcanism on the Kaapvaal craton: deepening the orangeite versus lamproite debate 

      Tappe, Sebastian; Shaikh, Azhar M.; Wilson, Allan H.; Stracke, Andreas (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-02)
      Orangeites are a significant source of diamonds, yet ambiguity surrounds their status among groups of mantle-derived potassic rocks. This study reports mineralogical and geochemical data for a c. 140 Ma orangeite dyke swarm that intersects the Bushveld Complex on the Kaapvaal craton in South Africa. The dykes comprise distinctive petrographic varieties that are linked principally by olivine ...
    • Exceptions to bed-controlled ice sheet flow and retreat from glaciated continental margins worldwide 

      Greenwood, Sarah L.; Simkins, Lauren M; Winsborrow, Monica; Bjarnadóttir, Lilja Rún (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-13)
      Projections of ice sheet behavior hinge on how ice flow velocity evolves and the extent to which marine-based grounding lines are stable. Ice flow and grounding line retreat are variably governed by the coupling between the ice and underlying terrain. We ask to what degree catchment-scale bed characteristics determine ice flow and retreat, drawing on paleo-ice sheet landform imprints from 99 sites ...
    • Excess water storage induced by viscous strain localization during high-pressure shear experiment 

      Précigout, Jacques; Stünitz, Holger; Villeneuve, Johan (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-05)
      Strain localization in viscously deformed rocks commonly results in fine-grained shear zones where massive fluid circulation is regularly observed. Recently attributed to strain-induced pumping, this phenomenon may have major implications for the distribution of ores deposits and rock rheology. However, although grain size reduction and/or creep cavitation have been proposed as important processes, ...
    • Exhumation of the High‐Pressure Tsäkkok Lens, Swedish Caledonides: Insights From the Structural and White Mica 40Ar/39Ar Geochronological Record 

      Barnes, C.J.; Jeanneret, P.; Kullerud, Kåre; Majka, J.; Schneider, D.A.; Bukala, M.; Klonowska, I. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-12)
      Integrated structural, geochemical, and geochronological investigations were conducted on metasedimentary rocks in the eclogite-bearing Tsäkkok Lens of the Seve Nappe Complex (Scandinavian Caledonides) to resolve its exhumation history. Three deformation events are defined. D1 is likely related to the prograde to peak-metamorphic stages, represented by a locally preserved S1. D2 resulted in vertical ...