English
norskArtikler, rapporter og annet (geovitenskap): Nye registreringer
Viser treff 501-520 av 804
-
Mississippian rocks and WNW–ESE-striking faults in Spitsbergen
(Conference object; Konferansebidrag, 2019-06-18) -
Impact of Timanian thrusts on the Phanerozoic tectonic history of Svalbard
(Conference object; Konferansebidrag, 2019-09-13)Despite more than a century of investigation, the relationship between basement rocks throughout the Svalbard Archipelago is still a mystery. Though these rocks display similar geochronological ages, they show significantly different metamorphic grades and structures. Thus far, Svalbard was believed to be composed of three terranes of rocks formed hundreds–thousands of kilometers apart and accreted ... -
Dissolved Inorganic Geogenic Phosphorus Load to a Groundwater-Fed Lake: Implications of Terrestrial Phosphorus Cycling by Groundwater
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-10-24)The general perception has long been that lake eutrophication is driven by anthropogenic sources of phosphorus (P) and that P is immobile in the subsurface and in aquifers. Combined investigation of the current water and P budgets of a 70 ha lake (Nørresø, Fyn, Denmark) in a clayey till-dominated landscape and of the lake’s Holocene trophic history demonstrates a potential significance of geogenic ... -
Long-term fluid expulsion revealed by carbonate crusts and pockmarks connected to subsurface gas anomalies and palaeo-channels in the central North Sea
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-11-19)Gas seepage through the seafloor into the water column is inferred based on acoustic mapping, video observations and geochemical analyses at multiple locations in the Viking Graben and Utsira High areas of the central North Sea. Flares in the Viking Graben occur both inside and along the periphery of a submarine melt water channel where pockmarks (up to 500 m in diameter) and methane-derived carbonate ... -
Changes in sea ice cover and ice sheet extent at the Yermak Plateau during the last 160 ka - Reconstructions from biomarker records
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-02-15)The Yermak Plateau is located north of Svalbard at the entrance to the Arctic Ocean, i.e. in an area highly sensitive to climate change. A multi proxy approach was carried out on Core PS92/039-2 to study glacial-interglacial environmental changes at the northern Barents Sea margin during the last 160 ka. The main emphasis was on the reconstruction of sea ice cover, based on the sea ice proxy ... -
Polyphase kinematic history of transpression along the Mecca Hills segment of the San Andreas fault, southern California
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-09)Miocene–Pliocene sedimentary rocks in the Mecca Hills, southern California, were uplifted and deformed by transpression along a restraining bend in the San Andreas fault trace between the Orocopia and San Bernardino Mountains in Pleistocene time. This paper presents field evidence for three stages of structural evolution of a complex, asymmetric wedge-like flower structure, expressed as: (1) ... -
Excess water storage induced by viscous strain localization during high-pressure shear experiment
(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, ... -
Methane-fuelled biofilms predominantly composed of methanotrophic ANME-1 in Arctic gas hydrate-related sediments
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-05)Sedimentary biofilms comprising microbial communities mediating the anaerobic oxidation of methane are rare. Here, we describe two biofilm communities discovered in sediment cores recovered from Arctic cold seep sites (gas hydrate pingos) in the north-western Barents Sea, characterized by steady methane fluxes. We found macroscopically visible biofilms in pockets in the sediment matrix at the depth ... -
The Permafrost Young Researchers Network (PYRN) is getting older – the past, present, and future of our evolving community
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-07)A lasting legacy of the International Polar Year (IPY) 2007–2008 was the promotion of the Permafrost Young Researchers Network (PYRN), initially an IPY outreach and education activity by the International Permafrost Association (IPA). With the momentum of IPY, PYRN developed into a thriving network that still connects young permafrost scientists, engineers, and researchers from other disciplines. ... -
Variability of Acoustically Evidenced Methane Bubble Emissions Offshore Western Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-22)Large reservoirs of methane present in Arctic marine sediments are susceptible to rapid warming, promoting increasing methane emissions. Gas bubbles in the water column can be detected, and flow rates can be quantified using hydroacoustic survey methods, making it possible to monitor spatiotemporal variability. We present methane (CH<sub>4</sub>) bubble flow rates derived from hydroacoustic data ... -
Discharge of Meteoric Water in the Eastern Norwegian Sea since the Last Glacial Period
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-03)Submarine groundwater discharge could impact the transport of critical solutes to the ocean. However, its driver(s), significance over geological time scales, and geographical coverage are poorly understood. We characterize a submarine groundwater seep from the continental slope off northern Norway where substantial amount of meteoric water was detected. We reconstruct the seepage history from ... -
A novel biomarker-based proxy for the spring phytoplankton bloom in Arctic and sub-arctic settings – HBI T25
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-19)The spring phytoplankton bloom is a characteristic feature of mid-high latitudes in modern times, but can be challenging to identify in palaeo records. In the current study, we investigated the absolute and relative distributions of two diatom-derived tri-unsaturated highly branched isoprenoid (HBI) lipids, at least one of which has previously been suggested to be a possible proxy for the productive ... -
Hydrate occurrence in Europe: A review of available evidence
(Journal article; Tidsskriftartikkel, 2019-08-16)Large national programs in the United States and several Asian countries have defined and characterised their marine methane hydrate occurrences in some detail, but European hydrate occurrence has received less attention. The European Union-funded project “Marine gas hydrate – an indigenous resource of natural gas for Europe” (MIGRATE) aimed to determine the European potential inventory of exploitable ... -
Evolución ambiental de los estuarios del Geoparque de la costa Vasca durante el Holoceno y el Antropoceno
(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 ... -
Experimental grain growth of quartz aggregates under wet conditions and its application to deformation in nature
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-13)Grain growth of quartz was investigated using two quartz samples (powder and novaculite) with water under pressure and temperature conditions of 1.0–2.5 GPa and 800–1100 ∘C. The compacted powder preserved a substantial porosity, which caused a slower grain growth than in the novaculite. We assumed a grain growth law of <i>d<sup>n</sup>−d<sup>n</sup><sub>0</sub>=k</i><sub>0</sub><i>f<sup>r</sup><su ... -
High-resolution underwater laser spectrometer sensing provides new insights into methane distribution at an Arctic seepage site
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-13)Methane (CH4) in marine sediments has the potential to contribute to changes in the ocean and climate system. Physical and biochemical processes that are difficult to quantify with current standard methods such as acoustic surveys and discrete sampling govern the distribution of dissolved CH4 in oceans and lakes. Detailed observations of aquatic CH4 concentrations are required for a better understanding ... -
A 160,000-year-old history of tectonically controlled methane seepage in the Arctic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-07)The geological factors controlling gas release from Arctic deep-water gas reservoirs through seabed methane seeps are poorly constrained. This is partly due to limited data on the precise chronology of past methane emission episodes. Here, we use uranium-thorium dating of seep carbonates sampled from the seabed and from cores drilled at the Vestnesa Ridge, off West Svalbard (79°N, ~1200 m water ... -
Anticlockwise metamorphic pressure–temperature paths and nappe stacking in the Reisa Nappe Complex in the Scandinavian Caledonides, northern Norway: evidence for weakening of lower continental crust before and during continental collision
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019)This study investigates the tectonostratigraphy and metamorphic and tectonic evolution of the Caledonian Reisa Nappe Complex (RNC; from bottom to top: Vaddas, Kåfjord, and Nordmannvik nappes) in northern Troms, Norway. Structural data, phase equilibrium modelling, and U-Pb zircon and titanite geochronology are used to constrain the timing and pressure–temperature (<i>P–T</i>) conditions of deformation ... -
The Origin of Gas Seeps in the Northern Adriatic Sea
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06)A multidisciplinary approach has been used for the first time to study the widespread occurrence of hydrocarbon seeps in the northern Adriatic Sea. Geological, geophysical and geochemical analyses were performed to identify and characterize the gas-charged fluids occurring throughout the Plio-Quaternary succession, and to date the shallow gas seeping at three leakage sites. The analysis of CHIRP, ... -
Palaeoceanographic reconstruction of surface-ocean changes in the southern Norwegian Sea for the last ~130,000 years based on diatoms and with comparison to foraminiferal records
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-28)Fossil marine diatom assemblages in a sediment core from the central northern Faroe slope in the Norwegian Sea were used to reconstruct palaeoceanographic changes in the surface water mixed layer from the last ~130,000 years (Marine Isotope Stage (MIS) 6/5 transition to MIS 1 (including the Eemian and Holocene interglacials) and to compare the results with previously published results on planktic ...
