Institutt for geovitenskap: Nye registreringer
Viser treff 561-580 av 1034
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Seismic sequence analysis and petroleum system indicators at the Oligocene-Miocene level in the southern North Sea
(Master thesis; Mastergradsoppgave, 2019-05-14)A thorough review of the Oligocene-Miocene stratigraphic evolution and depositional environments in the Norwegian part of the southern North Sea is presented and considered alongside observations of petroleum system indicators, from seismic-, core- and well-data. The reconstructed paleo-environments show a trend of fluctuating eustatic sea-levels, controlled by basin subsidence and uplift of the ... -
Direct 40Ar/39Ar K‐feldspar dating of Late Permian–Early Triassic brittle faulting in Northern Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-04-23)While the offshore post‐Caledonian extensional history of the north Norwegian passive margin is well constrained, the tectonic relationship between onshore and offshore regions is less clear because of limited age constraints on the timing of rifting onshore. <sup>40</sup>Ar/<sup>39</sup>Ar dating of K‐feldspar from hydrothermally altered fault rocks in a Precambrian gneiss complex in northern Norway ... -
The dinoflagellate cyst genera Achomosphaera Evitt 1963 and Spiniferites Mantell 1850 in Pliocene to modern sediments: a summary of round table discussions
(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 ... -
On the causes of Arctic sea ice in the warm Early Pliocene
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-30)Scattered and indirect evidence suggests that sea ice occurred as far south as the Iceland Sea during the Early Pliocene, when the global climate was warmer than present. However, conclusive evidence as well as potential mechanisms governing sea ice occurrence outside the Arctic Ocean during a time with elevated greenhouse gas concentrations are still elusive. Here we present a suite of organic ... -
Greenland Ice Sheet surface melt amplified by snowline migration and bare ice exposure
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-06)Greenland Ice Sheet mass loss has recently increased because of enhanced surface melt and runoff. Since melt is critically modulated by surface albedo, understanding the processes and feedbacks that alter albedo is a prerequisite for accurately forecasting mass loss. Using satellite imagery, we demonstrate the importance of Greenland’s seasonally fluctuating snowline, which reduces ice sheet albedo ... -
Authigenesis of biomorphic apatite particles from Benguela upwelling zone sediments off Namibia: The role of organic matter in sedimentary apatite nucleation and growth
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-30)Sedimentary phosphorites comprise a major phosphorus (P) ore, yet their formation remains poorly understood. Extant polyphosphate‐metabolizing bacterial communities are known to act as bacterial phosphate‐pumps, leading to episodically high dissolved phosphate concentrations in pore waters of organic‐rich sediment. These conditions can promote the precipitation of amorphous precursor phases that are ... -
Reconstruction of ice sheet retreat after the Last Glacial maximum in Storfjorden, southern Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-15)Storfjorden is a large north-south trending sound located in the southern part of Svalbard in the northwestern Barents Sea. Presently, several glaciers drain into the northern and western part of Storfjorden. Our study area covers the southern part of the sound, which is divided by a north-south striking basement ridge (the ‘Mid-ridge’) into a narrow western trough (‘Little-Storfjorden’) and a broader ... -
Multiple sulphur isotope records tracking basinal and global processes in the 1.98 Ga Zaonega Formation, NW Russia
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-09-19)The exceptionally organic-rich rocks of the 1.98 Ga Zaonega Formation deposited in the Onega Basin, NW Russia, have refined our understanding of Earth System evolution during the Paleoproterozoic rise in atmospheric oxygen. These rocks were formed in vent- or seep influenced settings contemporaneous with voluminous mafic volcanism and contain strongly <sup>13</sup>C-depleted organic matter. ... -
Mineralogical and Geochemical Constraints on Magma Evolution and Late-Stage Crystallization History of the Breivikbotn Silicocarbonatite, Seiland Igneous Province in Northern Norway: Prerequisites for Zeolite Deposits in Carbonatite Complexes
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-20)The present work reports on new mineralogical and whole-rock geochemical data from the Breivikbotn silicocarbonatite (Seiland igneous province, North Norway), allowing conclusions to be drawn concerning its origin and the role of late fluid alteration. The rock shows a rare mineral association: calcite + pyroxene + amphibole + zeolite group minerals + garnet + titanite, with apatite, allanite, ... -
Life on the edge: Active microbial communities in the Kryos MgCl2-brine basin at very low water activity
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-04-17)The Kryos Basin is a deep-sea hypersaline anoxic basin (DHAB) located in the Eastern Mediterranean Sea (34.98°N 22.04°E). It is filled with brine of re-dissolved Messinian evaporites and is nearly saturated with MgCl<sub>2</sub>-equivalents, which makes this habitat extremely challenging for life. The strong density difference between the anoxic brine and the overlying oxic Mediterranean seawater ... -
Quaternary interaction of cryospheric and oceanographic processes along the central-east Greenland margin
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-16)The east Greenland margin has been influenced by oceanographic and cryospheric processes since the late Miocene, when the southwards flow of the East Greenland Current (EGC) initiated and ice sheets first advanced across the margin. However, the relative importance of these processes, and their influence on the sedimentation of the margin through time remains poorly understood. High‐resolution ... -
Modelling persistent methane seepage offshore western Svalbard since early Pleistocene
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-31)Recent observations of extensive methane release into the oceans and atmosphere have raised concern as to whether rising temperatures across the Arctic could drive rapid destabilization of gas hydrate reservoirs. Here, we report modelling results from hydrate-modulated methane seepage from Vestnesa Ridge, offshore western Svalbard, suggesting that continuous leakage has occurred from the seafloor ... -
An assessment of biomarker-based multivariate classification methods versus the PIP25 index for paleo Arctic sea ice reconstruction
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-30)The development of various combinative methods for Arctic sea ice reconstruction using the sympagic highly-branched isoprenoid (HBI) IP<sub>25</sub> in conjunction with pelagic biomarkers has often facilitated more detailed descriptions of sea ice conditions than using IP<sub>25</sub> alone. Here, we investigated the application of the Phytoplankton-IP<sub>25</sub> index (PIP<sub>25</sub>) and a ... -
Early and Middle Pleistocene environments, landforms and sediments in Scotland
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-10-04)This paper reviews the changing environments, developing landforms and terrestrial stratigraphy during the Early and Middle Pleistocene stages in Scotland. Cold stages after 2.7 Ma brought mountain ice caps and lowland permafrost, but larger ice sheets were short-lived. The late Early and Middle Pleistocene sedimentary record found offshore indicates more than 10 advances of ice sheets from ... -
Quantification of the magnitude of net erosion in the southwest Barents Sea using sonic velocities and compaction trends in shales and sandstones
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-09-19)During specific intervals within Mesozoic and Cenozoic times, several areas of the southwestern Barents Sea were subjected to uplift and erosion. Areas with missing shallow stratigraphic interval sections and major erosion can be seen at several places along interpreted regional profiles in the southwestern Barents Sea. A new Normal Compaction Trend (NCT) for two selected shale– and ... -
Atypical biological features of a new cold seep site on the LofotenVesterålen continental margin (northern Norway)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-11)A newly discovered cold seep from the Lofoten-Vesterålen margin (Norwegian Sea) is dominated by the chemosymbiotrophic siboglinid <i>Oligobrachia haakonmosbiensis</i> like other high latitude seeps, but additionally displays uncharacteristic features. Sulphidic bottom water likely prevents colonization by cnidarians and sponges, resulting in fewer taxa than deeper seeps in the region, representing ... -
Monitoring Of CO2 Leakage Using High-Resolution 3D Seismic Data – Examples From Snøhvit, Vestnesa Ridge And The Western Barents Sea
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-21)Injection of CO2 in subsurface reservoirs may cause overburden deformation and CO2 leakage. The aim of this study is to apply technologies for detection and monitoring of CO2 leakage and deformation above the injection reservoirs. The examples of this study include data from the Vestnesa Ridge natural seep site, the Snøhvit gas field and CO2 storage site region, and the Gemini North gas reservoir. ... -
Syn-kinematic hydration reactions, grain size reduction, and dissolution-precipitation creep in experimentally deformed plagioclase-pyroxene mixtures
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-09)It is widely observed that mafic rocks are able to accommodate high strains by viscous flow. Yet, a number of questions concerning the exact nature of the involved deformation mechanisms continue to be debated. In this contribution, rock deformation experiments on four different water-added plagioclase–pyroxene mixtures are presented:(i) plagioclase(An60–70)–clinopyroxene–orthopyroxene,(ii) ... -
Rockfall hazard assessment based on semi-automatic point cloud analysis from UAV data
(Master thesis; Mastergradsoppgave, 2018-12-29)Slettind in Flaktstad municipality, Lofoten in Nordland, has numerous rockfalls throughout the year. Rockfalls hit Fv 805 on a weekly basis, and it is estimated the most dangerous road in Nordland county. A rock avalanche hit the road winter 2017 closing it for 2 weeks, and isolating the small village Myrland. Statens Vegvesen consider to build a tunnel to protect the road but the failure mechanisms ... -
Characterization of Carbonate Crust from a Recently Discovered Methane Seep on the North Atlantic Continental Margin of the USA
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-26)This study is focused on mineralogical and chemical characterization of an authigenic carbonate rock (crust) collected at a recently discovered cold seep on the US North Atlantic continental margin. X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicate that the carbonate rock is composed of microcrystalline aragonite cement, white acicular aragonite crystals (AcAr), equant quartz ...