Now showing items 141-160 of 1046

    • Widespread partial-depth hydrofractures in ice sheets driven by supraglacial streams 

      Chandler, David Matthew; Hubbard, Alun (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-19)
      Dramatic supraglacial lake drainage events in Greenland and Antarctica are enabled by rapid hydrofracture propagation through ice over 1 km thick. Here we present a slower mode of hydrofracture, where hairline surface fractures intersect supraglacial streams, and hypothesize that penetration depth is critically limited by water supply and englacial refreezing. We develop a model of stream-fed ...
    • The Paleoarchean Buffalo River komatiites: Progressive melting of a single large mantle plume beneath the growing Kaapvaal craton 

      Netshidzivhe, Thendo; Tappe, Sebastian; Wilson, Allan H.; Ishikawa, Akira; Viljoen, Fanus (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-01)
      Several Archean granitoid-greenstone terranes are exposed on the southeastern Kaapvaal craton in South Africa, but they received little scientific attention compared to the archetypal greenstone belt successions of the Barberton Mountain Land at the eastern craton margin. This study reports on a detailed field and geochemical survey of the Buffalo River Greenstone Belt at the southern Kaapvaal craton ...
    • Palaeoceanographic and climate changes during the Holocene in Hinlopen Strait, northern Svalbard 

      Hosseini, Mehdi (Mastergradsoppgave; Master thesis, 2023-05-20)
      This study investigates the paleoceanographic changes in the Hinlopen Strait, situated between Spitsbergen and Nordaustlandet, through a multi-proxy analysis of sediment core HH15-1280-GC (439 m water depth). Located near the Polar Front, this region is highly sensitive to even minor alterations in the ocean circulation and climate, which can be reconstructed from marine sediment records. The core ...
    • Garnet growth and mineral geochronology constrains the diachronous Neoproterozoic convergent evolution of the southern Dom Feliciano Belt, Uruguay 

      Percival, Jack James; Konopásek, Jiří; Oyhantçabal, Pedro; Slama, Jiri; Anczkiewicz, Robert (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-15)
      The Dom Feliciano Belt of southern Brazil and Uruguay represents part of a larger Neoproterozoic orogenic system formed during the amalgamation of Western Gondwana. The hinterland and foreland domains in parts of the belt preserve deformation structures and metamorphic assemblages that developed during early crustal thickening from c. 650 Ma. However, the metamorphic history of the southern foreland, ...
    • Plume–lithosphere interactions and LIP-triggered climate crises constrained by the origin of Karoo lamproites 

      Tappe, Sebastian; Ngwenya, Ntando S.; Stracke, Andreas; Romer, Rolf L.; Glodny, Johannes; Schmitt, Axel K. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-20)
      We identified a ca. 180 Ma diamondiferous lamproite event in Zambia, establishing a link between ultrapotassic volcanism and the early Jurassic Karoo flood basalt province of sub-Saharan Africa. The cratonic lamproites erupted through the Permo–Triassic Luangwa Rift structure, but MgO-rich ultrapotassic magma formation was unrelated to rifting and triggered by plume–lithosphere interactions during ...
    • Gas seeps in Norwegian waters – distribution and mechanisms 

      Thorsnes, Terje; Chand, Shyam; Bellec, Valerie Karin; Nixon, Chantel; Brunstad, Harald; Lepland, Aivo; Aarrestad, Sigrun M. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-01)
      Gas seeps and fluid-flow related seabed features are found over the entire Norwegian exclusive economic zone (EEZ). Multibeam water-column data from c. 136 000 km2 has revealed more than 5 000 gas seeps. Most of the gas seeps seem to have biogenic, thermogenic or mixed origin; some may be of abiotic origin. The spatial distribution of the gas seeps appears to correlate with: 1 – structural highs ...
    • Multiproxy reconstruction of past methane emissions at Storfjordrenna Pingos site (South of Svalbard) during the last deglaciation 

      Paavilainen, Anne (Mastergradsoppgave; Master thesis, 2023-05-15)
      The main ambition of this thesis was to study the relationship between isotopic signature of fossil foraminifera and past methane emission at Storfjordrenna Pingos site (South of Svalbard) during the last deglaciation in context of past climatic changes. Two gravity cores, the core 1070 from the flank of the presently inactive gas hydrate pingo 5 (GHP5) and the core 1069 from the top of the ...
    • Late Quaternary paleoceanography of Vestnesa Ridge, Fram Strait: Ostracode species as a potential indicator of cold seep activity 

      Chu, Rachel W.C.; Yasuhara, Moriaki; Myrvang Riise, Karoline; Asahi, Hirofumi; Huang, Huai-Hsuan May; Cotton, Laura J.; Hong, Yuanyuan; Rasmussen, Tine Lander (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-02)
      Past intensity of methane release from deep-ocean methane hydrates continues to be challenging to reconstruct reliably. Here, we used fossil ostracode fauna paired with foraminiferal δ<sup>13</sup>C values in a marine sediment core from Vestnesa Ridge, western Svalbard margin, to reconstruct methane seepage activity during the late Quaternary and to examine faunal response to deglacial climatic ...
    • Sedimentary ancient DNA: a new paleogenomic tool for reconstructing the history of marine ecosystems 

      Nguyen, Ngoc-Loi; Devendra, Dhanushka; Szymanska, Natalia; Greco, Mattia; Barrenechea Angeles, Inés Andrea; Weiner, Agnes K. M.; Ray, Jessica Louise; Cordier, Tristan; De Schepper, Stijn; Pawłowski, Jan; Pawłowska, Joanna (Journal article; Tidsskriftartikkel, 2023-06-09)
      Sedimentary ancient DNA (sedaDNA) offers a novel retrospective approach to reconstructing the history of marine ecosystems over geological timescales. Until now, the biological proxies used to reconstruct paleoceanographic and paleoecological conditions were limited to organisms whose remains are preserved in the fossil record. The development of ancient DNA analysis techniques substantially expands ...
    • Bivalve beds reveal rapid changes in ocean oxygenation in the Boreal Middle Triassic – a case study from Svalbard, Norway 

      Engelschiøn, Victoria Sjøholt; Bernhardsen, Sofie; Wesenlund, Fredrik; Hammer, Øyvind; Hurum, Jørn Harald; Mørk, Atle (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-17)
      A fossil-rich interval in the organic-rich marine black mudstone of the Middle Triassic Botneheia Formation on eastern Svalbard was logged in high-resolution on an extremely well exposed section with emphasis on bivalve beds, taphonomic features, trace fossils and oxygenation proxies. The size distribution, fragmentation, articulation and orientation of three bivalve beds of the epifaunal flat ...
    • Microphone recording of flexural waves for estimation of lake ice thickness 

      Romeyn, Rowan Peter; Hanssen, Alfred (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-20)
      In this study we took an intentionally low-tech approach, aiming to estimate key physical parameters of lake ice using a single, inexpensive microphone. We consider this approach highly relevant to the issue of transport safety and the relatively high number of accidents involving breakthrough failure of thin ice underlines the importance of this topic. We conducted a range of experiments on three ...
    • Climate-controlled submarine landslides on the Antarctic continental margin 

      Gales, Jenny A.; Mckay, Robert M.; De Santis, Laura; Rebesco, Michele; Laberg, Jan Sverre; Shevenell, Amelia E; Harwood, David; Leckie, R. Mark; Kulhanek, Denise K.; King, Maxine; Patterson, Molly; Lucchi, Renata G.; Kim, Sookwan; Kim, Sunghan; Dodd, Justin; Seidenstein, Julia; Prunella, Catherine; Ferrante, Giulia M. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-18)
      Antarctica’s continental margins pose an unknown submarine landslide-generated tsunami risk to Southern Hemisphere populations and infrastructure. Understanding the factors driving slope failure is essential to assessing future geohazards. Here, we present a multidisciplinary study of a major submarine landslide complex along the eastern Ross Sea continental slope (Antarctica) that identifies ...
    • The Heliconoides Modified Dissolution Index-HMDI: Do methane seepage environments affect the preservation state of Heliconoides inflatus? 

      Beccari, Valentina; Almogi-Labin, Ahuva; Basso, Daniela; Panieri, Giuliana; Makovsky, Yizhaq; Neururer, Christoph; Hajdas, Irka; Spezzaferri, Silvia (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-24)
      Pteropods are holoplanktonic molluscs presently endangered because their fragile aragonitic shell is very sensitive to ocean acidification. The preservation of pteropods, and in particular of the mesopelagic Heliconoides (Limacina) inflatus, has been used to assess aragonite saturation state in Quaternary sediments (Limacina Dissolution Index, LDX) as an inferred proxy for climatic changes. Three ...
    • Deep-water sand transfer by hyperpycnal flows, the Eocene of Spitsbergen, Arctic Norway 

      Grundvåg, Sten-Andreas; Helland-Hansen, William; Johannessen, Erik P.; Eggenhuisen, Joris T.; Pohl, Florian; Spychala, Yvonne T. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-11)
      Flood-generated hyperpycnal flows are dense, sediment-laden, turbulent flows that can form long-lived, bottom-hugging turbidity currents, which undoubtedly transport large volumes of fine-grained sediments into the ocean. However, their ability in transferring sand into deep-water basins is debated. This study presents sedimentological evidence of sandy hyperpycnal flow deposits (hyperpycnites) in ...
    • An investigation into the causal factors of the Kråknes landslide 

      Sandnes, Torgrim (Mastergradsoppgave; Master thesis, 2021-05-15)
      On the 3rd of June 2020, a landslide measuring 600 meters long and 160 meters wide initiated along the shoreline at Kråknes, in Alta municipality in Troms and Finnmark County. The landslide was comprised of a series of smaller slides, which destroyed eight houses and a caravan in the process. Fortunately, no human lives were lost in the event. Due to the widespread presence of sensitive clays along ...
    • Advances in understanding subglacial meltwater drainage from past ice sheets 

      Simkins, Lauren M; Greenwood, Sarah L.; Winsborrow, Monica; Bjarnadóttir, Lilja Rún; Lepp, Allison (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-17)
      Meltwater drainage beneath ice sheets is a fundamental consideration for understanding ice–bed conditions and bed-modulated ice flow, with potential impacts on terminus behavior and iceshelf mass balance. While contemporary observations reveal the presence of basal water movement in the subglacial environment and inferred styles of drainage, the geological record of former ice sheets, including ...
    • The Hambergfjellet Formation on Bjørnøya – sedimentary response to early Permian tectonics on the Stappen High 

      Grundvåg, Sten-Andreas; Strand, Mathias; Paulsen, Christian Oen; Simonsen, Bjørn; Røstad, Jostein; Mørk, Atle; Mørk, Mai Britt Engeness (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-14)
      On Bjørnøya, the exhumed crest of the Stappen High, the lower Permian (Cisuralian) Hambergfjellet Formation represents the only exposed part of the Bjarmeland Group carbonate platform, which occurs widely elsewhere in the subsurface of the Barents Shelf. A complex stratigraphic architecture has earlier been noted for the Hambergfjellet Formation and thickness estimates range from c. 50 to more than ...
    • Can big data and random forests improve avalanche runout estimation compared to simple linear regression? 

      Toft, Håvard B.; Müller, Karsten; Hendrikx, Jordy; Jaedicke, Christian; Bühler, Yves (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-05)
      Accurate prediction of snow avalanche runout-distances in a deterministic sense remains a challenge due to the complexity of all the physical properties involved. Therefore, in many locations including Norway, it has been common practice to define the runout distance using the angle from the starting point to the end of the runout zone (α-angle). We use a large dataset of avalanche events from ...
    • Spatial Changes in Gas Transport and Sediment Stiffness Influenced by Regional Stress: Observations From Piezometer Data Along Vestnesa Ridge, Eastern Fram Strait 

      Plaza-Faverola, Andreia; Sultan, Nabil; Lucchi, Renata Giulia; El bani Altuna, Naima; Ramachandran, Hariharan; Singhroha, Sunny; Cooke, Frances Ann; Vadakkepuliyambatta, Sunil; Mohamed, Mohamed Mahmoud Ezat Ahmed; Rasmussen, Tine Lander (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-25)
      Gas transport through sediments to the seabed and seepage occurs via advection through pores, faults, and fractures, and as solubility driven gas diffusion. The pore pressure gradient is a key factor in these processes. Yet, in situ measurements for quantitative studies of fluid dynamics and sediment deformation in deep ocean environments remain scarce. In this study, we integrate piezometer data, ...
    • Widespread subseafloor gas hydrate in the Barents Sea and Norwegian Margin 

      Cook, A.E.; Portnov, Alexey; Heber, R.C.; Vadakkepuliyambatta, Sunil; Bünz, Stefan (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-01)
      The distribution and concentration of subseafloor natural gas hydrate across margins is not well understood, because these systems are challenging to image and quantify remotely. Furthermore, it is unknown if shallow hydrate systems are linked to deeper oil and gas reservoirs. Herein, we analyze petroleum industry well logs with data in the gas hydrate stability zone and find that low concentrations ...