Munin: Browsing Mastergradsoppgaver i geologi by Title

Holocene climate variability in the Norwegian current and North Cape current inferred from benthic stable isotope records

Johannessen, Hilde B. (Master thesis; Mastergradsoppgave, 14-Jun-2006)

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Holocene sedimentary environments in Smeerenburgfjorden, Spitsbergen

Velle, Julie Heggdal (Master thesis; Mastergradsoppgave, 15-Nov-2012)

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Abstract:

Multi-proxy analyses of six sediment cores (including lithostratigraphy, physical properties, granulometric analyses, and XRF scanning), and analyses of swath bathymetry and chirp data were integrated to elucidate the Holocene sedimentary processes and palaeoenvironments in Smeerenburgfjorden, northwest Spitsbergen. Three basins separated by two sills define the present-day large-scale bathymetry. A transverse ridge in the innermost part of the fjord represents the Little Ice Age (LIA) maximum position of Smeerenburgbreen. Slide scars along the fjord sides and mass transport deposits in the basins indicate repeated mass wasting. Recessional moraines deposited during the last deglaciation suggest a mean annual retreat rate of 140 m/year. Another set of recessional moraines deposited between the maximum LIA position of Smeerenburgbreen and its present day terminus indicate a mean retreat rate of the ice front of ~87 m/year. Although only some of the recessional moraines deposited during the last deglaciation are expressed on the modern seafloor, chirp data reveal that they occur throughout the entire fjord. Suspension settling, ice rafting and mass wasting are the main sedimentary processes acting in Smeerenburgfjorden. Suspension settling is most important in the inner parts of the fjord, resulting in high sedimentation rates that rapidly decrease with increasing distance from the main sediment sources. Strong out-fjord decreasing trends in magnetic susceptibility and Fe-content indicate that these properties are related to material originating from the Hornemantoppen granite in the catchment of Smeerenburgbreen and are, thus, useful proxies for the reconstruction of the activity of the glacier. Relatively little ice rafting, most likely related to warmer surface water conditions, occurred between 8650 and 7350 cal. years BP. Ice rafting from both sea-ice and icebergs increased around 6200 cal. years BP and peaked at ~5200 cal. years BP, associated with a regional cooling. Smeerenburgbreen became more active around 2000 cal. years BP. It probably retreated during the Roman Warm Period (50 BC – AD 400) and advanced during the Dark Ages Cold Period (AD 400 – 800). From AD 1300 – 1500 (late Medieval Warm Period; AD 900 – 1500), ice rafting, sedimentation rates and productivity increased in the inner fjord. The Little Ice Age was characterised by reduced ice rafting, possibly linked to an increased sea-ice cover suppressing iceberg drift. An increase in Ice Rafted Debris (IRD) commencing around AD 1880 is suggested to represent the beginning of Smeerenburgbreen’s retreat from its LIA maximum towards its present position.

URI:

http://hdl.handle.net/10037/4650

File(s) in this item: 1

thesis.pdf (12.51Mb)

Landform assemblages in inner Kongsfjorden, Svalbard: evidence of recent glacial (surge) activity

Streuff, Katharina Teresa (Master thesis; Mastergradsoppgave, 15-May-2013)

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Abstract:

Swath bathymetry and chirp data have been used to investigate the submarine landform assemblages in inner Kongsfjorden, Svalbard, to reconstruct glacial dynamics during the Late Holocene. Multiple sets of landforms include two types of glacial lineations (groove-ridge features and small, drumlinoid ridges), terminal moraines and associated debris lobes, as well as small push moraines, and indicate repeated surge activity during the last 150 years for four of the five tidewater glaciers terminating in inner Kongsfjorden. Aside from confirming previously documented surges of Kronebreen in 1869, of Kongsvegen, in 1948, and of Blomstrandbreen in 1960, the local bathymetry also indicates a surge of Kongsbreen in 1897, a glacier that has so far been regarded as a non-surge type glacier. A conceptual model was developed to summarize the surge-induced landform assemblages in Kongsfjorden, and to compare them with other models from terrestrial and marine settings. Striking similarities exist between the Kongsfjorden model and landform assemblages documented for other Spitsbergen fjords. However, eskers and crevasse-fill ridges, the latter thought to be the only landform certainly indicative of glacier surges, lack in Kongsfjorden. Furthermore, the small, drumlinoid ridges inferred to be suggestive of the past ice flow direction in the study area seem to have more in common with glacial lineations generated by surging glaciers on land. The acoustic data was supplemented with two sediment cores from Kongsfjorden’s innermost basin. The reworked glacimarine deposits at the base of the more proximal core reflect proximal conditions, as they are part of a debris lobe that formed on the distal flank of the terminal moraine deposited during the 1948 surge of Kongsvegen. The stratified muds from the second core contain varying amounts of clasts and also occur on top of the debris lobe. They reveal a relatively distal glacimarine environment mainly influenced by suspension settling from turbid meltwater emanating from Kronebreen or Kongsvegen. Geochemical fluctuations indicate temporal variations in the sediment supply from the two glaciers after 1948. The few landforms in the outer parts of the study area suggest glacial activity unrelated to the glacier surges. Together with the landforms previously documented from outer Kongsfjorden and its adjacent trough (Kongsfjordrenna), the mega-scale glacial lineations in the outer part of the study area indicate part of a landform assemblage deposited from a fast-flowing ice stream during the Last Glacial Maximum.

URI:

http://hdl.handle.net/10037/5212

File(s) in this item: 1

thesis.pdf (8.736Mb)

Late Paleozoic-Cenozoic fault correlation and characterization of fault rocks in western Troms, North Norway

Koehl, Jean-Baptiste Philippe (Master thesis; Mastergradsoppgave, 29-May-2013)

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Abstract:

The present work focuses on the mapping and description of onshore brittle fault zones on the SW Barents Sea Margin, within gneisses and granitic intrusions belonging to the West Troms Basement Complex. The description of the brittle structures includes the geometry, kinematics and fault rock characteristics, using DEM satellite imaging, structural field work and a microstructural analysis of the fault rocks. As a result of the present study,two major sets of onshore brittle faults have been observed, trending NNE-SSW and ENE-WSW,and they are tentatively correlated in two, NE-SW trending fault complexes: the Rekvika and the Vestfjorden-Vanna fault complexes. These fault complexes run parallel to the Troms-Finnmark fault complex that borders major offshore sedimentary basins in the NW. On the one hand, the Vestfjorden-Vanna fault complex defines the southeastern boundary of the West Troms Basement Complex towards the Caledonian nappes, and is made of wide fault zones that have experienced major displacement (ca. 1-3km). On the other hand, the Rekvika fault complex is considered as an intra-horst fault system composed of narrow fault zones that are thought to have accommodated low amounts of displacement (> 250 m). On a local scale, the fault zones display similarities in attitude (trend and dip) with the Caledonian and Precambrian fabrics, indicating a possible influence of pre-existing zones of weakness on brittle faulting. The dominant deformation mechanism (cataclastic flow) indicates pressure range about 0.2-0.3 GPa, i.e. 5-10 km depth for the formation of the cataclastic fault rocks, and these fault rocks contain mineral assemblages that generally indicate temperatures about 350-500ᵒC. This suggests that the West Troms Basement Complex has been largely uplifted later on, until present level. The NNE-SSW and ENE-WSW trending fracture sets are believed to have formed synchronously due to WNW-ESE extension, during an early stage of rifting in the Permian-Early Triassic. The NNE-SSW trending faults likely represent the main fault system, orthogonal to the extension direction, and the ENE-WSW trending faults may correspond to oblique transfer zones that link the NNE-SSW fault segments. An alternative model implies NW-SE trending transfer zones to link the NNE-SSW trending faults. A late stage of minor reverse reactivation of the NNE-SSW and ENE-WSW trending faults, and the development of NW-SE striking fractures are tentatively correlated to ridge-push forces during the opening of the North Atlantic in the Eocene.

URI:

http://hdl.handle.net/10037/5214

File(s) in this item: 1

thesis.pdf (8.426Mb)

Late Weichselian and Holocene sedimentary processes and environments in Billefjorden, Svalbard

Baeten, Nicole Jeanne (Master thesis; Mastergradsoppgave, Nov-2007)

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Abstract:

Three sediment cores, swath multibeam bathymetry data and high-resolution seismic data from Billefjorden, Svalbard have been analysed for a better understanding of the Late Weichselian and Holocene glacier activity as well as sedimentary process and glacigenic deposits in the fjord. The data reveal that glacial linear features were generated in the central part of Billefjorden while it was filled with ice draining the Svalbard-Barents Sea ice sheet during the Last Glacial. A till in the bottom of a sediment core from the central part of the fjord is inferred to have been deposited before the ice front retreated into Billefjorden around 11230 cal. years BP. An overlying glacimarine unit deposited between c. 11230 and 11200 cal. years BP indicates that the glacier retreated from central parts of the fjord to the fjord head in approximately 30 years. Annual recessional moraines deposited during this period suggest that the glacier front retreated approximately 330 m/ year at the end of the last Glacial. High concentration of shells, low amounts of IRD and XRD results indicate a Holocene climatic optimum between c. 11200 – 7930 cal. years BP in which Nordenskiöldbreen was most likely much smaller than it is at present. XRD results and comparatively high amounts of IRD point to a complex pattern of ice rafting between c. 7930 and 3230 cal. BP. IRD deposited before c. 5470 cal. years BP was most likely transported by sea ice, whereas IRD after 5470 cal. years points towards a growth of Nordenskiöldbreen. The time after c. 3230 is mainly characterised by suppressed rafting of sea ice and icebergs because of the possible presence of multi-year shorefast sea ice during the Neoglacial maximum. Glacial lineations on a bedrock terrace in the inner fjord were formed during a Neoglacial advance of Nordenskiöldbreen. Iceberg ploughmarks and recessional moraines were most likely generated during the retreat after the maximum Neoglacial extent of Nordenskiöldbreen. Mass-transport activity in Billefjorden probably occurred throughout the entire Holocene. There might haven been an increased mass-transport activity shortly after the deglaciation of the fjord, because high rates of isostatic uplift might have caused seismic activity. Other triggering mechanisms include the development of oversteepened slopes by high sediment supply and the pushing of sediments at the grounding line of the glacier. Pockmarks in the central part of the fjord were most likely generated by the seepage of thermogenic gas along the Billefjorden fault zone.

URI:

http://hdl.handle.net/10037/1274

File(s) in this item: 1

Thesis.pdf (42.43Mb)

Microstructural and metamoprhic study in rocks of the Seiland Igneous Province between Langfjord and Øksfjord, Alta kommune, Northern Norway

Rustad, Birgit Katrine (Master thesis; Mastergradsoppgave, 22-Nov-2010)

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Abstract:

The Seiland Igneous Province (SIP) is situated in western Finnmark, Northern Norway. The SIP comprises a suite of mainly gabbroic plutons, with ultramafic, syenitic and felsic intrusions. The origin of the region has been interpreted in different ways and several tectonic models have been proposed. Many different ideas have been suggested about the metamorphic, magmatic and deformation history. New age dates by Roberts (2008) fall within a narrow time range, from 555 Ma to 579 Ma, concluding that the main magmatism took place within ten million years. This is a much shorter period than previously estimated, and the deformation and metamorphic history of the province is therefore reconsidered. In order to better understand the metamorphic and deformation history of the SIP, studies on microstructures, deformation and metamorphism have been carried out in this thesis on a gabbroic pluton and a strongly sheared quartz-feldspathic xenolith of the Seiland Igneous province situated between Langfjord and Øksfjord. Observations from the field and thin sections indicate that the metamorphic and deformational history of these two rocks can be divided into the following stages: contact metamorphism of the country rock caused by the emplacement of the plutonic gabbro (stage I) with subsequent cooling (stage II) and following loading probably as a result of nappe emplacement during the Caledonian orogeny (stage III). Microstructures and metamorphic reactions observed in the rocks support pressure and- temperature estimates given by Elvevold et al. (1994). Both rock types show evidence of a cooling and subsequent solid state deformation. The cooling stage was followed by a higher-pressure metamorphism interpreted to be related to emplacement of a tectonic unit of cold thrust sheet over hot rock during the Caledonian orogeny. The nappe emplacement resulted in the formation of thin mylonitic zones recognized by a strong grain size reduction and a replacement of a pyroxene granulite assemblage to a garnet granulite assemblage. The foliation seen in the Suborg-gabbro and the quartz-feldspathic gneiss is suggested to be a result of extension associated with continental rifting. The emplacement of the Suborg-gabbro is believed to have taken place during regional deformation. The foliation in the Suborg-gabbro shows evidence of magmatic flow overprinted by a solid state flow. Kinematic indictors observed in the quartz-feldspathic xenolith indicate normal faulting supporting extension and a rifting model for the SIP. Keywords: Seiland Igneous Province, metamorphism, deformation, extension.

URI:

http://hdl.handle.net/10037/2897

File(s) in this item: 1

thesis.pdf (12.40Mb)

Overgangen fra eklogitt til amfibolitt. Et detaljstudium

Øiesvold, Marte Beate (Master thesis; Mastergradsoppgave, May-2007)

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Abstract:

Formålet med oppgaven er å gjøre en systematisk petrografisk og petrologisk undersøkelse av en mafisk linse med omgivende granat-glimmerskifer/marmor innen Tromsødekket. Den mafiske linsa har opprinnelig sannsynlig vært en basaltisk gang/sill som har blitt metamorfosert under eklogittfacies. Lokaliteten er blottlagt i ei veiskjæring ved universitetet i Tromsø (UiT). Den valgte mafiske linsa har en tilnærmet udeformert kjerne, og graden av deformasjon og hydrering tiltar mot marginene mot de omgivende sterkt folierte skifere og marmorer. Den mafiske linsa har også en gjennomskjærende felsisk gang som er deformert. Lokaliteten er derfor godt egnet til å se på den gradvise endringen fra massiv og retrogradert eklogitt (høytrykksgranulitt) via ulike retrograderingsstadier til sterkt foliert og rekrystallisert amfibolitt. Datering av den gjennomskjærende felsiske gangen vil kunne gi informasjon om når retrograderingen skjedde. Tromsødekket utgjør den øverste delen av øverste allokton i de Skandinaviske kaledonidene. Under Tromsødekket ligger Skattøra migmatittkompleks, som tilhører Nakkedal dekkekompleks, disse er tektonisk separert av en stor skyveforkastning. Resultatene er basert på dateringer og metamorf utvikling. Proterozoiske aldre på henholdsvis 1105,0 ± 8,6 (Grenvillisk/Svekonorvegisk alder) og 1513,6 ± 3,1 Ma er antatt å representere provenansalder for metasedimentene, og de kan ha blitt termalt påvirket samtidig som intrusjon av den magmatiske gangen/sillen rundt 493 Ma. Avsetningsalderen på sedimentene må da være i tidsrommet 1000-500 Ma. Opptreden av rekrystalliserte symplektitter og stedvis høyt Si-innhold i phengitt tyder på at de mafiske bergartene sannsynligvis har vært eklogitter. De mafiske bergartene viser en overpreging av amfibolittfacies. Det antas at den felsiske gangen er dannet ved oppsmelting av de omliggende metapelittene. Gangen kan ha blitt inturdert under amfibolittfacies metamorfosen ved 447,7 ± 0,5 Ma eller muligens rundt 460 Ma. Granatene i de mafiske bergartene har en prograd vekstsonering og har vokst under økende trykk og temperatur. P-T estimatene viser at både amfibolittfacies metamorfosen og den partielle oppsmeltingen i den mafiske linsa er dannet under samme P-T forhold på 1,15 ± 0,11 GPa og 690 ± 40 °C. Metapelittene viser P-T estimat på 1,15 ± 0,15 GPa ved 710 ± 30 °C og ned til 610 ± 30 °C ved samme trykk (1,1 ± 0,15 GPa). Dette kan tolkes som at den kjemiske ekvilibreringen i noen prøver fortsatte ettersom temperaturen avtok etter at de kjemiske systemene hadde ”frosset” i de andre bergartene.

URI:

http://hdl.handle.net/10037/1140

File(s) in this item: 1

Thesis.pdf (6.694Mb)

Pinchout geometry of sheet-like sandstone beds: a new statistical approach to the problem of lateral bed thinning based on outcrop measurements

Janocko, Michal (Master thesis; Mastergradsoppgave, 22-Feb-2008)

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Abstract:

The pinch-out geometry of large sandbodies, such as fluvial or turbiditic palaeochannel margins and deltaic sand wedges, is of a crucial importance to the evaluation of many stratigraphic hydrocarbon traps and can generally be recognized in extensive outcrops or high-resolution seismic sections. Far more difficult to recognize and model are the digitate, feather-edge pinchouts of successions composed of sheet-like sandstone beds, such as turbidite lobes or shore-derived mid-shelf tempestites, where the individual beds may peter out at highly varied basinward distances. Both turbidites and tempestites are expected to pinch out seawards, but their actual thinning rates and pinchout geometries are little-known and unpredictable. Can the lateral variation of sheet-like bed characteristics be empirically defined? In the present pilot study, more than 3750 closely-spaced (2-10 m lateral spacing) measurements of the lateral thickness changes in 146 turbidite and tempestite beds have been collected over lateral outcrop distances of up to 640 m. Turbidites have been measured in the Miocene Marnoso Arenacea Formation of the Northern Apennines, Italy, and the Late Cretaceous Akveren Formation of the Central Pontides, north-central Turkey, with supplementary smaller datasets from the Eocene Kusuri Formation of the Central Pontides and the Miocene Monte Fumaiolo Formation of the Northern Apennines. Tempestites have been measured in the late Miocene Karpuzçay Formation in the Manavgat Basin of Central Taurides, south-western Turkey. The spatial direction of bed thinning relative to the palaeocurrent direction has been taken into account. The datasets show that both turbidites and tempestites have a log-normal thickness frequency distribution, a trend that has been also commonly reported from bed-to-bed thickness measurements of vertical successions. In terms of an exceedence frequency plot with logarithmic scales, the log-normal distribution can be approximated by straight-line segments, which means that the bed thicknesses are self-similar (fractal) within their particular ranges. The statistical method of least-square regression has been used to identify lateral bed-thinning trends, which appear to be consistent for each genetic category of beds, but dependent upon the bed thickness range – as the downflow bed thinning rate apparently changes significantly with the bed thickness. Assuming the bed segments measured in outcrop sections represent downflow-thinning segments of unconfined (non-ponded) basin-plain turbidites and shelf tempestites, their thinning rates can be stacked together according to the local bed-thickness ranges to represent the pinchout geometry of a whole single bed. The stacking of local trends into a laterally continuous bulk trend seems to be justified by the fact that the thinner bed segments are finer-grained and composed of proportionally thinner divisions. The synthetic bulk trend appears to be a concave-upward function that flattens exponentially in the downflow direction. The range-related trend equations allow the pinchout distance of every bed in a turbiditic or tempesitic succession encountered in a well to be predicted and the net spatial pinch-out of a given bed succession to be modelled. However, the trend equations are considered to be tentative, as they require veritication on a wider database. In addition, the statistical analysis revealed occurrence of bed-top undulations in both turbidites and tempestites, which are subtle to gentle and are visually unrecognizable in outcrop sections. Fourier analysis indicates statistically significant, cyclic waveform components in these undulations, with wavelengths of up to 300 m and amplitudes from a few centimetres to 60 cm. The tops of thinner beds have less pronounced and more irregular subtle undulations. The origin of the bed-top undulations is unknown, but there are several wave-like hydrualic phenomena, such as internal waves, to which they may possibly owe their formation.

URI:

http://hdl.handle.net/10037/1356

File(s) in this item: 2

Janocko_Errata.pdf (126.6Kb)

thesis.pdf (26.89Mb)

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