Now showing items 650-669 of 711

    • Teaching with digital geology in the high Arctic: opportunities and challenges 

      Senger, Kim; Betlem, Peter; Grundvåg, Sten-Andreas; Horota, Rafael Kenji; Buckley, Simon John; Smyrak-Sikora, Aleksandra; Jochmann, Malte Michel; Birchall, Thomas; Janocha, Julian; Ogata, Kei; Kuckero, Lilith; Johannessen, Rakul Maria; Lecomte, Isabelle Christine; Cohen, Sarah M.; Olaussen, Snorre (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-09-28)
      <p>The Covid-19 pandemic occurred at a time of major revolution in the geosciences – the era of digital geology. Digital outcrop models (DOMs) acquired from consumer drones, processed using user-friendly photogrammetric software and shared with the wider audience through online platforms are a cornerstone of this digital geological revolution. Integration of DOMs with other geoscientific data, such ...
    • 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 ...
    • The tectonized central peak of the Mjølnir Impact Crater, Barents Sea 

      Corseri, Romain; Gac, Sebastien; Faleide, Jan Inge; Planke, Sverre (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-12-04)
      The Mjølnir structure, SW Barents Sea, is one of the best-preserved marine impact craters on Earth. After impact on the paleo-seafloor about 142 Ma ago, this crater experienced an atypical deformation of its central peak, which is now elevated ~435 m above the crater rims. Here, we investigate the effect of far-field tectonic stresses on the central peak uplift based on interpretation of new ...
    • Tectono-Metamorphic Evolution of the Northern Dom Feliciano Belt Foreland, Santa Catarina, Brazil: Implications for Models of Subduction-Driven Orogenesis 

      Percival, Jack James; Konopásek, Jiří; Anczkiewicz, Robert; Ganerød, Morgan; Slama, Jiri; Campos, Roberto Sacks de; Bitencourt, Maria de Fatima (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-27)
      The Dom Feliciano Belt in southern Brazil and Uruguay represents the western half of a Neoproterozoic orogenic belt located in the southern portion of the South Atlantic Neoproterozoic Orogenic System. Current interpretations are divided as to the nature of orogenesis in this belt, in part owing to lacking geochronological constraints. Metamorphosed and deformed supracrustal sequences of the Brusque ...
    • Temperature observations from northernmost Greenland, 2006-2010 

      Schomacker, Anders; Larsen, Nicolaj K.; Bjørk, Anders A.; Kjær, Kurt H. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-03-31)
      Air-, surface-, and subsurface temperatures were recorded by automatic weather stations in Bliss Bugt and Moore Gletscher, Johannes V. Jensen Land, North coast of Greenland from 2006-2010. The mean annual surface temperature is -12.1 ℃ in Bliss Bugt and -13.8 ℃ at Moore Gletscher. In 20 cm depth below the surface at Moore Gletscher, the mean annual temperature is -13.2 ℃ (2007-2008). High-amplitude ...
    • Tempestite facies variability and storm‐depositional processes across a wide ramp: Towards a polygenetic model for hummocky cross‐stratification 

      Jelby, Mads Engholm; Grundvåg, Sten-Andreas; Helland-Hansen, William; Olaussen, Snorre; Stemmerik, Lars (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-10-03)
      The hydrodynamic mechanisms responsible for the genesis and facies variability of shallow‐marine sandstone storm deposits (tempestites) have been intensely debated, with particular focus on hummocky cross‐stratification. Despite being ubiquitously utilized as diagnostic elements of high‐energy storm events, the full formative process spectrum of tempestites and hummocky cross‐stratification is still ...
    • Temporal and spatial structure of multi-millennial temperature changes at high latitudes during the Last Interglacial 

      Capron, Emilie; Govin, Aline; Stone, Emma J.; Masson-Delmotte, Valérie; Mulitza, Stefan; Otto-Bliesner, Bette; Rasmussen, Tine Lander; Sime, Louise C.; Waelbroeck, Claire; Wolff, Eric W. (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)
    • Temporal constraints on hydrate-controlled methane seepage off Svalbard 

      Berndt, Christian; Feseker, Tomas; Treude, Tina; Krastel, Sebastien; Liebetrau, Volker; Niemann, Helge; Bertics, Victoria; Dumke, Ines; Dünnbier, Karolin; Ferré, Benedicte; Graves, Carolyn; Gross, Felix; Hissmann, Karen; Hühnerbach, Veit; Krause, Stefan; Lieser, Kathrin; Schauer, Jürgen; Steinle, Lea (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-01-17)
      Methane hydrate is an icelike substance that is stable at high pressure and low temperature in continental margin sediments. Since the discovery of a large number of gas flares at the landward termination of the gas hydrate stability zone off Svalbard, there has been concern that warming bottom waters have started to dissociate large amounts of gas hydrate and that the resulting methane release may ...
    • Temporal Variability of Surface Reflectance Supersedes Spatial Resolution in Defining Greenland’s Bare-Ice Albedo 

      Irvine-Fynn, Tristram D. L.; Bunting, Peter S.; Cook, Joseph M.; Hubbard, Alun; Barrand, Nicholas E.; Hanna, Edward; Hardy, Andy J.; Hodson, Andrew J.; Holt, Tom O.; Huss, Matthias; McQuaid, James B.; Nilsson, Johan; Naegeli, Kathrin; Roberts, Osian; Ryan, Jonathan C.; Tedstone, Andrew J.; Tranter, Martyn; Williamson, Christopher J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-23)
      Ice surface albedo is a primary modulator of melt and runoff, yet our understanding of how reflectance varies over time across the Greenland Ice Sheet remains poor. This is due to a disconnect between point or transect scale albedo sampling and the coarser spatial, spectral and/or temporal resolutions of available satellite products. Here, we present time-series of bare-ice surface reflectance data ...
    • 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 ...
    • A Theoretical Model of Drumlin Formation Based on Observations at Múlajökull, Iceland 

      Iverson, N. R.; McCracken, R. G.; Zoet, L. K.; Benediktsson, Í. Ö.; Schomacker, Anders; Johnson, M. D.; Woodard, J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-20)
      The drumlin field at the surge‐type glacier, Múlajökull, provides an unusual opportunity to build a model of drumlin formation based on field observations in a modern drumlin‐forming environment. These observations indicate that surges deposit till layers that drape the glacier forefield, conform to drumlin surfaces, and are deposited in shear. Observations also indicate that erosion helps create ...
    • Thermal Characterization of Pockmarks Across Vestnesa and Svyatogor Ridges, Offshore Svalbard 

      Riedel, M.; Villinger, H.; Freudenthal, T.; Pape, T.; Bünz, Stefan; Bohrmann, G. (Journal article; Tidsskriftartikkel, 2020-11-10)
      The Svalbard margin represents one of the northernmost gas hydrate provinces worldwide. Vestnesa Ridge (VR) and Svyatogor Ridge (SR) west of Svalbard are two prominent sediment drifts showing abundant pockmarks and sites of seismic chimney structures. Some of these sites at VR are associated with active gas venting and were the focus of drilling and coring with the seafloor‐deployed MARUM‐MeBo70 ...
    • Thermal state of the Guaymas Basin derived from gas hydrate bottom simulating reflections and heat flow measurements 

      Sarkar, Sudipta; Moser, Manuel; Berndt, Christian; Doll, Mechthild; Böttner, Christoph; Chi, Wu-Cheng; Klaeschen, Dirk; Galerne, Christophe; Karstens, Jens; Geilert, Sonja; Mortera-Gutierrez, C.; Hensen, Christian (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-20)
      Seafloor heat flow provides information about the thermal evolution of the lithosphere, the magnitude and timing of volcanic activity, and hydrothermal circulation patterns. In the central Gulf of California, the Guaymas Basin is part of a young marginal spreading rift system that experiences high sedimentation (1–5 km/Myr) and widespread magmatic intrusions in the axial troughs and the off-axis ...
    • Thermogenic methane injection via bubble transport into the upper Arctic Ocean from the hydrate-charged Vestnesa Ridge, Svalbard 

      Smith, Andrew James; Mienert, Jurgen; Bünz, Stefan; Greinert, Jens (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-04-21)
      We use new gas‐hydrate geochemistry analyses, echosounder data, and three‐dimensional P‐Cable seismic data to study a gas‐hydrate and free‐gas system in 1200 m water depth at the Vestnesa Ridge offshore NW Svalbard. Geochemical measurements of gas from hydrates collected at the ridge revealed a thermogenic source. The presence of thermogenic gas and temperatures of ∼3.3°C result in a shallow top of ...
    • Tidal Energy Loss, Internal Tide Radiation, and Local Dissipation for Two-Layer Tidal Flow over a Sill 

      Arneborg, Lars; Jansson, Pær; Staalstrøm, Andre; Broström, Göran (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-14)
      A simple analytical model for tidal energy loss at fjord sills and its partitioning into local dissipation and radiated internal tides is presented. The analytical model builds on a two-layer assumption with quasi-steady nonlinear flow over the sill and wave radiation in the far field. When the interface is situated above sill level, upstream- and downstream-propagating internal waves are generated ...
    • Til IBGs 20-års-jubileum 

      Labugt, Sylvia (Kronikk; Chronicle, 1992)
    • A time-transgressive perspective of glacial erosion and meltwater beneath the Eurasian ice sheet 

      Patton, Henry Jared; Hubbard, Alun Lloyd; Heyman, Jakob; Alexandropoulou, Nikolitsa; Lasabuda, Amando P. E.; Stroeven, Arjen P; Hall, Adrian; Winsborrow, Monica Caroline Mackay; Sugden, David A.; Kleman, Johan; Shackleton, Calvin; Da Silveira Ramos Esteves, Mariana; Bjarnadóttir, Lilja Rún; Andreassen, Karin Marie (Conference object; Konferansebidrag, 2023-08)
      The efficacy and controls governing glacial erosion over geological timescales are intricately linked yet remain poorly understood and contended. By assimilating geophysical data with modelling of the Eurasian Ice Sheet - the third largest Quaternary ice mass that spanned 49°N - 82°N - we decipher its erosional footprint during the last ~110 ka glacial cycle. Our results demonstrate extreme ...
    • Timescales of methane seepage on the Norwegian margin following collapse of the Scandinavian Ice Sheet 

      Cremiere, Antoine; Lepland, Aivo; Chand, Shyam; Sahy, Diana; Condon, Daniel J.; Noble, Stephen R.; Martma, Tõnu; Thorsnes, Terje; Sauer, Simone; Brunstad, Harald (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-05-11)
      Gas hydrates stored on continental shelves are susceptible to dissociation triggered by environmental changes. Knowledge of the timescales of gas hydrate dissociation and subsequent methane release are critical in understanding the impact of marine gas hydrates on the ocean–atmosphere system. Here we report a methane efflux chronology from five sites, at depths of 220–400 m, in the southwest Barents ...
    • TitaniQ temperatures and textural analysis as a record of the deformation history in a major continental shear zone system, Borborema Province, Brazil 

      Cavalcante, Carolina; de Jesus Costa, Juliana; Lagoeiro, Leonardo; Fossen, Haakon; Lee, Amicia; Archanjo, Carlos; Vizeu, Roberto (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-09-01)
      We combine quartz textural analysis with Titanium-in-quartz (TitaniQ) geothermometry to investigate the late stages of deformation in mylonitic rocks from the Sucuru dike swarm in the Borborema Province. The wide range in TitaniQ temperatures (>340 to 740 °C) closely related to grain sizes are attributed to inefficient Ti resetting during bulging (BLG) and subgrain rotation (SGR) recrystallization. ...
    • Towards an improved organic carbon budget for the western Barents Sea shelf 

      Pathirana, Irene Dorothea; Knies, Jochen; Felix, Maarten; Mann, Ute (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-03-21)
      There is generally a lack of knowledge on how marine organic carbon accumulation is linked to vertical export and primary productivity patterns in the Arctic Ocean. Despite the fact that annual primary production in the Arctic has increased as a consequence of shrinking sea ice, its effect on flux, preservation, and accumulation of organic carbon is still not well understood. In this study, a ...