37 results on '"Henriksen, Mona"'
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2. 200 ka of glacial events in NW Svalbard: an emergence cycle facies model and regional correlations
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Alexanderson, Helena, Henriksen, Mona, Ryen, Heidi T., Landvik, Jon Y., and Peterson, Gustaf
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- 2018
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3. A short-lived aeolian event during the Early Holocene in southeastern Norway
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Alexanderson, Helena and Henriksen, Mona
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- 2015
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4. Landscape imprints of changing glacial regimes during ice-sheet build-up and decay: a conceptual model from Svalbard
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Landvik, Jon Y., Alexanderson, Helena, Henriksen, Mona, and Ingólfsson, Ólafur
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- 2014
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5. Dynamics and retreat of the Late Weichselian Kongsfjorden ice stream, NW Svalbard
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Henriksen, Mona, Alexanderson, Helena, Landvik, Jon Y., Linge, Henriette, and Peterson, Gustaf
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- 2014
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6. Testing the reliability of quartz OSL ages beyond the Eemian
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Murray, Andrew, Buylaert, Jan-Pieter, Henriksen, Mona, Svendsen, John-Inge, and Mangerud, Jan
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- 2008
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7. Trening og angstlidelser - en litteraturstudie
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Henriksen, Mona Borsheim and Gabrielsen, Maren
- Abstract
Bacheloroppgave i fysioterapi, Høgskulen på Vestlandet, campus Bergen BFY330
- Published
- 2020
8. The periglacial climate and environment in northern Eurasia during the Last Glaciation
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Hubberten, Hans W, Andreev, Andrei, Astakhov, Valery I, Demidov, Igor, Dowdeswell, Julian A, Henriksen, Mona, Hjort, Christian, Houmark-Nielsen, Michael, Jakobsson, Martin, Kuzmina, Svetlana, Larsen, Eiliv, Lunkka, Juha Pekka, Lyså, Astrid, Mangerud, Jan, Möller, Per, Saarnisto, Matti, Schirrmeister, Lutz, Sher, Andrei V, Siegert, Christine, Siegert, Martin J, and Svendsen, John Inge
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- 2004
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9. Late Quaternary ice sheet history of northern Eurasia
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Svendsen, John Inge, Alexanderson, Helena, Astakhov, Valery I, Demidov, Igor, Dowdeswell, Julian A, Funder, Svend, Gataullin, Valery, Henriksen, Mona, Hjort, Christian, Houmark-Nielsen, Michael, Hubberten, Hans W, Ingólfsson, Ólafur, Jakobsson, Martin, Kjær, Kurt H, Larsen, Eiliv, Lokrantz, Hanna, Lunkka, Juha Pekka, Lyså, Astrid, Mangerud, Jan, Matiouchkov, Alexei, Murray, Andrew, Möller, Per, Niessen, Frank, Nikolskaya, Olga, Polyak, Leonid, Saarnisto, Matti, Siegert, Christine, Siegert, Martin J, Spielhagen, Robert F, and Stein, Ruediger
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- 2004
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10. Ice-dammed lakes and rerouting of the drainage of northern Eurasia during the Last Glaciation
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Mangerud, Jan, Jakobsson, Martin, Alexanderson, Helena, Astakhov, Valery, Clarke, Garry K.C, Henriksen, Mona, Hjort, Christian, Krinner, Gerhard, Lunkka, Juha-Pekka, Möller, Per, Murray, Andrew, Nikolskaya, Olga, Saarnisto, Matti, and Svendsen, John Inge
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- 2004
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11. Glacial and environmental changes over the last 60000years in the Polar Ural Mountains, Arctic Russia, inferred from a high-resolution lake record and other observations from adjacent areas
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Svendsen, John Inge, Færseth, Lars Martin B., Gyllencreutz, Richard, Haflidason, Haflidi, Henriksen, Mona, Hovland, Morten N., Lohne, Øystein S., Mangerud, Jan, Nazarov, Dmitry, Regnéll, Carl, Schaefer, Joerg M., Svendsen, John Inge, Færseth, Lars Martin B., Gyllencreutz, Richard, Haflidason, Haflidi, Henriksen, Mona, Hovland, Morten N., Lohne, Øystein S., Mangerud, Jan, Nazarov, Dmitry, Regnéll, Carl, and Schaefer, Joerg M.
- Abstract
Our knowledge about the glaciation history in the Russian Arctic has to a large extent been based on geomorphological mapping supplemented by studies of short stratigraphical sequences found in exposed sections. Here we present new geochronological data from the Polar Ural Mountains along with a high-resolution sediment record from Bolshoye Shchuchye, the largest and deepest lake in the mountain range. Seismic profiles show that the lake contains a 160-m-thick sequence of unconsolidated lacustrine sediments. A well-dated 24-m-long core from the southern end of the lake spans the last 24cal. ka. From downward extrapolation of sedimentation rates we estimate that sedimentation started about 50-60 ka ago, most likely just after a large glacier had eroded older sediments from the basin. Terrestrial cosmogenic nuclide (TCN) exposure dating (Be-10) of boulders and Optically Stimulated Luminescence (OSL) dating of sediments indicate that this part of the Ural Mountains was last covered by a coherent ice-field complex during Marine Isotope Stage (MIS) 4. A regrowth of the glaciers took place during a late stage of MIS 3, but the central valleys remained ice free until the present. The presence of small- and medium-sized glaciers during MIS 2 is reflected by a sequence of glacial varves and a high sedimentation rate in the lake basin and likewise from Be-10 dating of glacial boulders. The maximum extent of the mountain glaciers during MIS 2 was attained prior to 24cal. ka BP. Some small present-day glaciers, which are now disappearing completely due to climate warming, were only slightly larger during the Last Glacial Maximum (LGM) as compared to AD 1953. A marked decrease in sedimentation rate around 18-17cal. ka BP indicates that the glaciers then became smaller and probably disappeared altogether around 15-14cal. ka BP.
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- 2019
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12. A sedimentary model for transverse inland dunes in central Scandinavia
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Alexanderson, Helena, Bernhardson, Martin, Henriksen, Mona, and Kalinska-Nartisa, Edyta
- Subjects
Geology - Abstract
The largest dune fields in Sweden and Norway are small in international comparison but still form distinct parts of this previously glaciated landscape. The dunes formed c.10.5-9 ka ago, shortly after the last deglaciation, when winds close to the ice sheet were strong and vegetation was largely absent [1-4]. Since then they have been more or less stable and today they are covered by forest. Most of the dunes are curvi-linear in shape and formed transverse to the wind [5]. Here we present a sedimentary model for these transverse inland dunes, based on geophysical and sedimentological investigations of dunes at Skattungheden, Bonäsheden and Starmoen in central Sweden and south-eastern Norway. Ground-penetrating radar profiles reveal the main architectural elements of the dunes, while logging of sediment exposures in the dunes provide information on sedimentary structures. Grain-size analysis and scanning electron microscope studies of individual grains give us more detail on sediment characteristics.The main dune body, consisting of cross beds generally dipping 25-30°, makes up the largest part of the dunes; minor elements include windward side cover, dune-crest superimposed features and dune-toe apron (Fig. 1). The dominating sediment structures are planar parallel lamination, massive to vaguely stratified beds and a few types of secondary structures, such as bioturbation or physical disturbances. Few large erosional discordances are seen, and the dominating depositional processes are wind-ripple migration and some grain fall on the sloping lee sides. The sediments are well-sorted fine-to-medium sand, dominated by quartz, but with significant amounts of feldspar as well as some lithic fragments, micas and heavy minerals. Most grains are angular to subrounded and their surfaces display few traces of aeolian transport. Overall, the dune sands show large similarities to their source material (glacifluvial deposits), which suggests only short transport and brief reworking by aeolian processes.References[1] Alexanderson, H. and M. Bernhardson, OSL dating and luminescence characteristics of aeolian deposits and their source material in Dalarna, central Sweden Boreas, 2016. 45: p. 876-893.[2] Alexanderson, H. and M. Henriksen, A short-lived aeolian event during the Early Holocene in southeastern Norway. Quaternary Geochronology, 2015. 30: p. 175-180.[3] Bernhardson, M. and H. Alexanderson, Early Holocene NW-W winds reconstructed from small dune fields, central Sweden. Boreas, 2018.[4] Alexanderson, H. and D. Fabel, Holocene chronology of the Brattforsheden delta and inland dune field, SW Sweden. Geochronometria, 2015. 42: p. 1-16.[5] Bernhardson, M. and H. Alexanderson, Early Holocene dune field development in Dalarna, central Sweden: A geomorphological and geophysical case study. Earth Surface Processes and Landforms, 2017. 42: p. 1847-1859.
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- 2018
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13. Glacial and environmental changes over the last 60 000 years in the Polar Ural Mountains, Arctic Russia, inferred from a high‐resolution lake record and other observations from adjacent areas
- Author
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Svendsen, John Inge, primary, Færseth, Lars Martin B., additional, Gyllencreutz, Richard, additional, Haflidason, Haflidi, additional, Henriksen, Mona, additional, Hovland, Morten N., additional, Lohne, Øystein S., additional, Mangerud, Jan, additional, Nazarov, Dmitry, additional, Regnéll, Carl, additional, and Schaefer, Joerg M., additional
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- 2018
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14. Weichselian stratigraphy and glaciotectonic deformation along the lower Pechora River, Arctic Russia
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Henriksen, Mona, Mangerud, Jan, Maslenikova, Olga, Matiouchkov, Alexei, and Tveranger, Jan
- Published
- 2001
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15. Branched GDGT variability in sediments and soils from catchments with marked temperature seasonality
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Cao, Min, primary, Rueda, Gemma, additional, Rivas-Ruiz, Pedro, additional, Trapote, Mª Carmen, additional, Henriksen, Mona, additional, Vegas-Vilarrúbia, Teresa, additional, and Rosell-Melé, Antoni, additional
- Published
- 2018
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16. Dynamic Holocene glacial history of St. Jonsfjorden, Svalbard
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Farnsworth, Wesley R., primary, Ingólfsson, Ólafur, additional, Noormets, Riko, additional, Allaart, Lis, additional, Alexanderson, Helena, additional, Henriksen, Mona, additional, and Schomacker, Anders, additional
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- 2017
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17. Reconstructing the flow pattern evolution in inner region of the Fennoscandian Ice Sheet by glacial landforms from Gausdal Vestfjell area, south-central Norway
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Putniņš, Artūrs, primary and Henriksen, Mona, additional
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- 2017
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18. Glacial and environmental changes over the last 60 000 years in the Polar Ural Mountains, Arctic Russia, inferred from a high‐resolution lake record and other observations from adjacent areas.
- Author
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Svendsen, John Inge, Færseth, Lars Martin B., Gyllencreutz, Richard, Haflidason, Haflidi, Henriksen, Mona, Hovland, Morten N., Lohne, Øystein S., Mangerud, Jan, Nazarov, Dmitry, Regnéll, Carl, and Schaefer, Joerg M.
- Subjects
OPTICALLY stimulated luminescence ,ALPINE glaciers ,LAST Glacial Maximum ,GLACIAL landforms ,TUNDRAS ,WATERSHEDS ,COSMOGENIC nuclides - Abstract
Our knowledge about the glaciation history in the Russian Arctic has to a large extent been based on geomorphological mapping supplemented by studies of short stratigraphical sequences found in exposed sections. Here we present new geochronological data from the Polar Ural Mountains along with a high‐resolution sediment record from Bolshoye Shchuchye, the largest and deepest lake in the mountain range. Seismic profiles show that the lake contains a 160‐m‐thick sequence of unconsolidated lacustrine sediments. A well‐dated 24‐m‐long core from the southern end of the lake spans the last 24 cal. ka. From downward extrapolation of sedimentation rates we estimate that sedimentation started about 50–60 ka ago, most likely just after a large glacier had eroded older sediments from the basin. Terrestrial cosmogenic nuclide (TCN) exposure dating (10Be) of boulders and Optically Stimulated Luminescence (OSL) dating of sediments indicate that this part of the Ural Mountains was last covered by a coherent ice‐field complex during Marine Isotope Stage (MIS) 4. A regrowth of the glaciers took place during a late stage of MIS 3, but the central valleys remained ice free until the present. The presence of small‐ and medium‐sized glaciers during MIS 2 is reflected by a sequence of glacial varves and a high sedimentation rate in the lake basin and likewise from 10Be dating of glacial boulders. The maximum extent of the mountain glaciers during MIS 2 was attained prior to 24 cal. ka BP. Some small present‐day glaciers, which are now disappearing completely due to climate warming, were only slightly larger during the Last Glacial Maximum (LGM) as compared to AD 1953. A marked decrease in sedimentation rate around 18–17 cal. ka BP indicates that the glaciers then became smaller and probably disappeared altogether around 15–14 cal. ka BP. [ABSTRACT FROM AUTHOR]
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- 2019
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19. A short-lived aeolian event during the Early Holocene in southern Norway
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Alexanderson, Helena and Henriksen, Mona
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ComputingMilieux_LEGALASPECTSOFCOMPUTING ,Geology - Published
- 2014
20. Age and extent of the Barents and Kara ice sheets in Northern Russia
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Mangerud, Jan, Svendsen, John Inge, Astakhov, Valery I., Andreicheva, Ludmila, Funder, Svend, Henriksen, Mona, Hufthammer, Anne Karin, Indrelid, Svein, Matiouchkov, Alexei, Murray, Andrew, Paus, Aage, Pavlov, Pavel, Tveranger, Jan, and Ulvedal, Per
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Archeology ,geography ,Eemian ,geography.geographical_feature_category ,Ice stream ,Geology ,Antarctic sea ice ,Paleontology ,Ice core ,Moraine ,Ice age ,Glacial period ,Ice sheet ,Geomorphology ,Ecology, Evolution, Behavior and Systematics - Abstract
The youngest ice marginal zone between the White Sea and the Ural mountains is the W-E trending belt of moraines called the Varsh-Indiga-Markhida-Harbei-Halmer-Sopkay, here calledthe Markhida line. Glacial elements show that it was deposited by the Kara Ice Sheet, and in the west, by the Barents Ice Sheet. The Markhida moraine overlies Eemian marine sediments, and is therefore of Weichselian age. Distal to the moraine are Eemian marine sediments and three Palaeolithic sites with many C-14 dates in the range 16-37 ka not covered by till, proving that it represents the maximum ice sheet extension during the Weichselian. The Late Weichselian ice limit of M. G. Grosswald is about 400 km (near the Urals more than 700 km) too far south. Shorelines of ice dammed Lake Komi, probably dammed by the ice sheet ending at the Markhida line, predate 37 ka. We conclude that the Markhida line is of Middle/Early Weichselian age, implying that no ice sheet reached this part of Northern Russia during the Late Weichselian. This age is supported by a series of C-14 and OSL dates inside the Markhida line all of >45 ka. Two moraine loops protrude south of the Markhida line; the Laya-Adzva and Rogavaya moraines. These moraines are covered by Lake Komi sediments, and many C-14 dates on mammoth bones inside the moraines are 26-37 ka. The morphology indicates that the moraines are of Weichselian age, but a Saalian age cannot be excluded. No post-glacial emerged marine shorelines are found along the Barents Sea coast north of the Markhida line.
- Published
- 1999
21. Developing library e-learning courses - how to make a fruitful collaboration?
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Våga, Anne Beth, primary, Henriksen, Mona, primary, and Gåsemyr, Inger, primary
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- 2013
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22. Chronologies of the glacial history of Svalbard – a review
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Alexanderson, Helena, Henriksen, Mona, Landvik, Jon Y, Ryen, Heidi T, Alexanderson, Helena, Henriksen, Mona, Landvik, Jon Y, and Ryen, Heidi T
- Abstract
The basis of the glacial history of Svalbard lies in stratigraphic studies of terrestrial and marine geological records. Classic litho- and biostratigraphy give us local relative chronologies of events but to compare with other areas and records we are dependent on absolute age control. This presentation will focus on the Middle to Late Quaternary terrestrial record to which a range of different absolute dating techniques have been applied; these techniques all have their pros and cons regarding materials, resolution, age range, etc. Amino acid chronology, although not a strictly absolute dating method, may provide some age inferences. Radiocarbon dating of organic material such as shell and bone is still the most common technique and one that is generally considered reliable. It is however limited by its age range to the last ~50 ka, and our interest goes further back than so. Various versions of luminescence dating, particularly optically stimulated luminescence (OSL), have therefore become strong contenders during the recent decade, mainly due to their longer age range and applicability to a wider range of deposits than radiocarbon dating. Luminescence dating nevertheless has its drawbacks too, for Svalbard these are mainly related to the risk of incomplete bleaching (leading to age overestimation) and poor resolution (leading to large uncertainties for final ages). Other techniques that have been used on fossil material include electron spin resonance (ESR) and uranium-thorium (U/Th) dating. In common for most techniques is that we cannot date glacial events, but the intervening non-glacial (interstadial, interglacial) episodes. Cosmogenic exposure dating is an exception, which is also able to provide information on the thickness of ice sheets through time. From a geologist’s point of view we will discuss these different techniques, their usefulness and what we can expect of them. Do the dating methods meet our wishes regarding resolution? Are results from d
- Published
- 2010
23. The periglacial climate and environment in northern Eurasia during the Last Glaciation
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Hubberten, Hans-Wolfgang, Andreev, Andrei A., Astakhov, Valery I., Demidov, Igor, Dowdeswell, Julian A., Henriksen, Mona, Hjort, Christian, Houmark-Nielsen, Michael, Jakobsson, Martin, Kuzmina, Svetlana, Larsen, Eiliv, Lunkka, Juha Pekka, Lysa, Astrid, Mangerud, Jan, Möller, Per, Saarnisto, Matti, Schirrmeister, Lutz, Sher, Andrei V, Siegert, Christine, Siegert, Martin J., Svendsen, John Inge, Hubberten, Hans-Wolfgang, Andreev, Andrei A., Astakhov, Valery I., Demidov, Igor, Dowdeswell, Julian A., Henriksen, Mona, Hjort, Christian, Houmark-Nielsen, Michael, Jakobsson, Martin, Kuzmina, Svetlana, Larsen, Eiliv, Lunkka, Juha Pekka, Lysa, Astrid, Mangerud, Jan, Möller, Per, Saarnisto, Matti, Schirrmeister, Lutz, Sher, Andrei V, Siegert, Christine, Siegert, Martin J., and Svendsen, John Inge
- Abstract
This paper summarizes the results of studies of the Late Weichselian periglacial environments carried out in key areas of northern Eurasia by several QUEEN teams (European Science Foundation (ESF) programme: “Quaternary Environment of the Eurasian North”). The palaeoglaciological boundary conditions are defined by geological data on timing and extent of the last glaciation obtained in the course of the EU funded project “Eurasian Ice Sheets”. These data prove beyond any doubt, that with the exception of the northwestern fringe of the Taymyr Peninsula, the rest of the Eurasian mainland and Severnaya Zemlya were not affected by the Barents–Kara Sea Ice Sheet during the Last Glacial Maximum (LGM). Inversed modelling based on these results shows that a progressive cooling which started around 30 ka BP, caused ice growth in Scandinavia and the northwestern areas of the Barents–Kara Sea shelf, due to a maritime climate with relatively high precipitation along the western flank of the developing ice sheets. In the rest of the Eurasian Arctic extremely low precipitation rates (less than 50 mm yr−1), did not allow ice sheet growth in spite of the very cold temperatures. Palaeoclimatic and palaeoenvironmental conditions for the time prior to, during, and after the LGM have been reconstructed for the non-glaciated areas around the LGM ice sheet with the use of faunal and vegetation records, permafrost, eolian sediments, alluvial deposits and other evidences. The changing environment, from interstadial conditions around 30 ka BP to a much colder and drier environment at the culmination of the LGM at 20–15 ka BP, and the beginning of warming around 15 ka BP have been elaborated from the field data, which fits well with the modelling results.
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- 2004
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24. Intriguing climatic shifts in a 90 kyr old lake record from northern Russia
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HENRIKSEN, MONA, primary, MANGERUD, JAN, additional, MATIOUCHKOV, ALEXEI, additional, MURRAY, ANDREW S., additional, PAUS, AAGE, additional, and SVENDSEN, JOHN INGE, additional
- Published
- 2008
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25. Lake stratigraphy implies an 80 000 yr delayed melting of buried dead ice in northern Russia
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Henriksen, Mona, primary, Mangerud, Jan, additional, Matiouchkov, Alexei, additional, Paus, Aage, additional, and Svendsen, John Inge, additional
- Published
- 2003
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26. Ancient DNA and osteological analyses of a unique paleo-archive reveal Early Holocene faunal expansion into the Scandinavian Arctic.
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Boilard, Aurélie, Walker, Samuel J., Lødøen, Trond Klungseth, Henriksen, Mona, Takken Beijersbergen, Liselotte M, Star, Bastiaan, Robu, Marius, Tøssebro, Christine, Albrektsen, Cornelia Marie, Soleng, Yvonne, Aksnes, Sverre, Jørgensen, Roger, Hufthammer, Anne Karin, van Kolfschoten, Thijs, Lauritzen, Stein-Erik, Boessenkool, Sanne, Boilard, Aurélie, Walker, Samuel J., Lødøen, Trond Klungseth, Henriksen, Mona, Takken Beijersbergen, Liselotte M, Star, Bastiaan, Robu, Marius, Tøssebro, Christine, Albrektsen, Cornelia Marie, Soleng, Yvonne, Aksnes, Sverre, Jørgensen, Roger, Hufthammer, Anne Karin, van Kolfschoten, Thijs, Lauritzen, Stein-Erik, and Boessenkool, Sanne
- Abstract
Paleo-archives are essential for our understanding of species responses to climate warming, yet such archives are extremely rare in the Arctic. Here, we combine morphological analyses and bulk-bone metabarcoding to investigate a unique chronology of bone deposits sealed in the high-latitude Storsteinhola cave system (68°50' N 16°22' E) in Norway. This deposit dates to a period of climate warming from the end of the Late Glacial [~13 thousand calibrated years before the present (ka cal B.P.)] to the Holocene thermal maximum (~5.6 ka cal B.P.). Paleogenetic analyses allow us to exploit the 1000s of morphologically unidentifiable bone fragments resulting in a high-resolution sequence with 40 different taxa, including species not previously found here. Our record reveals borealization in both the marine and terrestrial environments above the Arctic Circle as a naturally recurring phenomenon in past periods of warming, providing fundamental insights into the ecosystem-wide responses that are ongoing today.
27. Groundwater conditions and development of Åsmåsan
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Tveraa, Mads Erik, Henriksen, Mona, and French, Helen Kristine
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Myrområder - Abstract
Bruk av geofysiske metoder for kartlegging av myrområder er mye brukt. Myrområder i seg selv er viktige for jordas karbon-balanse, og kontrollering av vannstand i flomperioder. Det er derfor viktig med gode undersøkelser av myrers utbredelse og grunnforhold. Åsmåsan, ved Ås i Viken, er en myr der det har blitt bygd opp et karbonlager i form av torv over flere tusen år. Myra er mye undersøkt av studenter og ansatte ved Norges miljø- og biovitenskapelige universitet (NMBU), både gjennom georadar (GPR), resistivitetsmålinger (ERT), kjerneprøver og grunnvannsundersøkelser. Under tidligere kartlegginger med georadar har signalet forsvunnet omtrent halvveis ned i myra, og hva som er grunn i dette er med på å danne grunnlaget for denne oppgaven. Det spekuleres i om dette kan knyttes til marine sedimenter under myrbassenget, eller omdanningen av organisk materiale i myra. For å si noe om utviklingen av Åsmåsan, samt forklare hva som kan være skyld i forsvinnende georadar-signaler i dypet av myra, er det utført kjemisk og vissuelle analyser av en torvkjerne hentet opp av myra. Undersøkelser med ERT ble også gjennomført, samt grunnvannsmålinger og modellering av grunnvann for å si noe om vannets oppholdstid i myra, og påvirkning fra årstidsvariasjoner av nedbør. Det er funnet høye verdier av elektrisk ledningsevne (EC) på 110-120 µS/cm, og lave pH-verdier på 3,74, i øvre 2 m av myra. For dypere deler er det funnet forhøyede verdier av Na og EC på henholdsvis 18 mg/L og 130 µS/cm, som trolig kan knyttes til diffusjon fra underliggende marine sedimenter. Målte verdier av EC for øvre 3 m av myra ble benyttet til å beregne penetrasjonsdyp for georadar på 3,5-3,9 m, som samsvarer omtrent med dypet der georadar-signalet forsvinner. Grunnvannsmodellen viser grunnvannsstrømning fra sør mot nord i myra, og det er beregnet oppholdstid for vann mellom 3,5 og 10 år avhengig av dyp i myra. Torvkjernen viser variasjoner av torvtilvekst og nedbrytning, som beskriver et varierende klima fra myras dannelse og fram til i dag. Geophysical methods are heavily used for mapping of peatlands. Peatlands are an important part of the Earths carbon cycle, and serve as a huge contribution to controlling the water balance in periods of flood. This proves the importance of good mappings of the extent and ground conditions in peatlands. Åsmåsan, close to Ås in Viken, is a bog in which carbon, in the form of peat, have accumulated over thousands of years. The bog is deeply studied by both students and employees at the Norwegian University of Life Sciences (NMBU), by the means of groundpenetrating radar (GPR), electrical resistivity tomography (ERT), core sampling and groundwater surveys. Previous mappings with GPR show a weakening of signals approximately half way through the bog, and exploiting the reason for this is one of the goals of this research. This might link with marine sediments below the peat basin, or the decomposition of organic matter in the bog. To explain the development of Åsmåsan, while finding out what is the reason for GPR signals disappearing half way through the bog, a peat core is studied and analyzed. The bog is surveyed with ERT, and measurements of the groundwater level and modelling of the groundwater flow are used to examine the retention time of water, and the effects from seasonal variations of precipitation. It is found high values of electric conductivity (EC), 110-120 µS/cm, and as low values of pH as 3.74 in the upper 2 m of the bog. For deeper segments it is found raised values of Na and EC, as much as 18 mg/L and 130 µS/cm. This is thought to come from diffusion from marine sediments below. The measured values of EC for the upper 3 m of the bog are used to calculate a penetration depth for GPR at 3.5-3.9 m. This is in accordance with the approximate depth of the disappearing GPR signals. Groundwater modelling show groundwater flow from south to north, and the calculated retention time of water is between 3.5 and 10 years, depending on depth. The peat core show variations in peat growth and decomposition, reflecting a varying climate from the formation of the bog and until today. M-MINA
- Published
- 2022
28. Paleoclimatic reconstruction from laminated lake sediments, Bødalsvatnet, Nordenskiöld Land, Svalbard
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Aasberg, Inger Marie Fausa, Henriksen, Mona, and Retelle, Michael
- Abstract
This thesis was conducted in connection with the University Centre in Svalbard: UNIS One predicted consequence of the current warming in the Arctic is an increase of heavy precipitation events. Svalbard have experienced an increase in total annual precipitation and air temperature have affected Svalbard’s environment, in particular the regional hydroclimate. The varved proglacial sediment record preserved in Bødalsvatnet, Nordenskiöld Land, Svalbard, contains a valuable climate signal that in this study is used to reconstruct changes in precipitation and temperature the last 150 years. The thesis uses a multi-proxy approach with varve count, physical parameters (grain size, magnetic susceptibility, dry bulk density, loss-onignition and water content) and geochemical analysis through X-ray fluorescence (K, Ca, Mn, Fe, Ti and Zr) of surface core BSV – 2019 – 1. Age determination of the surface core were cross corelated with a 2012 by varve count and plutonium (239+240Pu) measurement. Six turbidites (E1 – E6) were identified and dated to 1936, 1945, 1957, 1983 and 1993. The six turbidites relating to mass movement events lead on by intense precipitation thought to have exceeded the 2,5 mm per hour. The current threshold for the formation of mass moment events in Svalbard. The presence of a dropstone > 1 mm within deposits from the 1957 event was likely caused by an avalanche. The 1993 and 1983 events were likely triggered by high intensity warm rainstorms related to south westerly cyclones in November and March, respectively. The mass movement event of 1974 is connected to an intense heavy precipitation event where 34 mm of rain fell during a period of 12 hours. By cross-correlation to a longer - percussion core from 2012 the paleoclimatic record was extended to approximately 1844. The change in temperature and precipitation in combination with thicker lamina during the end of LIA has similarities to the current sedimentary record and needs to be investigated further. En forventet konsekvens av dagens oppvarming i Arktis er flere hendelser med intens nedbør. På Svalbard er har det vært en økning i total årlig nedbør og temperatur som har påvirket miljøet og da særlig hydroklimaet. Den proglasiale, årlige laminerte sedimenthistorien er bevart i Bødalsvatnet, Nordenskiöld Land, Svalbard. Den inneholder et viktig klimasignal som denne studien har brukt for å rekonstruere forandringer i nedbør og temperatur de siste 150 år. Denne oppgaven bruker en multi-proxy metode på overflatekjernen BVS-2019-1 basert på fysiske parametere (kornstørrelse, magnetisk susceptibilitet, tetthet, glødetap og vanninnhold) og kjemiske parameter ved røntgen-fluorescens (K, Ca, Mn, Fe, Ti og Zr). Aldersbestemmelse av sedimentkjernen er gjort ved å korrelere varv-telling fra 2019 med varv-telling og plutonium ( 239+240Pu) målinger fra et sediment kjerne tatt i 2012. Seks turbiditeter (E1 til E6) er identifisert og datert til 1936, 1945, 1957, 1974, 1981 og 1993. Turbiditetene er relatert til massebevegelseshendelser forårsaket av nedbør med en intensitet over 2,5 mm i timen, som er grenseverdi for massebevegelseshendelser på Svalbard. Forekomst av droppstein > 1mm er knyttet til hendelse i 1974, forårsaket av et snøskred. Hendelsene i 1983 og 1993 er knyttet til sør-vestlig sykloner som har ført til mild regnstorm med høy intensitet i henholdsvis mars og november. Hendelsen i 1974 er knyttet til intenst regnvær hvor det falt 34 mm regn over en periode på 12 timer. Ved å korrelere den lengre sediment kjernen fra 2012 ble den paleoklimatiske historien utvidet ytterligere, til ca. 1844. Forandringen i temperatur og nedbør sammen med tykkere lamina ved utgangen av LIA har likheter ved det nåværende sedimentære historien og trenger å bli studert ytterligere. M-MINA
- Published
- 2020
29. Kartlegging av kjemiske, fysiske og geologiske forhold i øvre Risa nedbørfelt som følge av fiskedødepisoder i elva Risa
- Author
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Hagen, Stine Maleen Thomassen, French, Helen Kristine, and Henriksen, Mona
- Subjects
Matematikk og Naturvitenskap: 400::Geofag: 450::Hydrogeologi: 467 [VDP] ,Risa ,Metaller ,Kjemi ,Geologi ,Grunnvann ,Fiskedød - Abstract
I elven Risa på Gardermosletta, på grensen til Ullensaker og Eidsvoll kommune, ble det i mai 2007, 2015 og juni 2016 observert død og svimet ørret. Fisken ble sett nedstrøms Risebru og ned til området ved Dalsdammen. Dette gikk svært hardt ut over ørretbestanden i elven, flere ørret ble samlet inn og det ble gjort undersøkelser av gjellene, da det ble observert et slimete belegg. Resultatene av gjelleanalysene viste at det var utfelling av metallene jern, aluminium og mangan. Det ble derfor antatt at årsaken til fiskedøden var kvelning som følger av metallpåslag. Siden episodene med fiskedød gikk hardt utover ørretbestanden i elva er Vannområdet Hurdalsvassdraget/Vorma, Ullensaker kommune og Risautvalget interessert i å vite hva som kan være kilden til metallene og hvorfor dette har skjedd episodisk. Det ble derfor utgangspunktet for problemstillingen i denne oppgaven, det ble utført undersøkelser i studieområdet for å forsøke å finne et svar på hva som kunne være årsakssammenhengen til fiskedødepisodene i Risa. For å forsøke å gi svar på hva som kan ha ledet til fiskedøden i Risa har det blitt gjort undersøkelser for å kartlegge kjemiske, fysiske og geologiske forhold i øvre Risa nedbørfelt. Både vannprøver og jordprøver har blitt tatt i disse områdene for å undersøke kjemien i området, her har det vært spesielt fokus på konsentrasjonen av metallene jern, aluminium og mangan. Det ble gjennomført geofysisk måling med GPR for å undersøke geologiske grunnforhold i området, som også har blitt undersøkt med mer direkte metoder som sonderboring, observasjonsbrønner og kornfordelingsanalyse. Grunnvannsstrømningen ble også forsøkt modellert med Modelmuse og ModFlow, for det er indikasjoner på at grunnvannet kan være kilde til jern siden Risa og Hersjøen er grunnvannsmatet. Det har ikke blitt funnet noe man kan peke på som årsak til episodene med fiskedød i Risa. Det er ikke mulig å gjøre videre undersøkelser på ørretens gjeller da dette materialet ikke ble tatt vare på etter analysene var gjort. Årsaken til at det kunne være interessant å gjøre andre undersøkelser av fisken er for å se om det var andre stoffer som kan være skadelig på ørret, og om det er en kombinasjon av flere parameter som har ledet til fiskedøden. Det er viktig å holde Risa under videre oppsikt og ha kontinuerlig oppfølging av elva for å kunne plukke opp store endringer som kan påvirke ørreten. In Risa river at Gardermosletta, at the borders of the municipalities Ullensaker and Eidsvoll, there were observed dying and dead brown trout. The fish were seen downstream Risebru and down to the area called Dalsdammen in May 2007, 2015 and June 2016. These episodes caused great damage on the brown trout population. Several trouts were collected and their gills was analyzed due to the fact that it was observed slimy coating on the gills. The results of the analysis of the gills showed precipitation of iron, aluminum and manganese. It was therefore assumed that the cause of the fish kills in Risa was due to respirational problems caused by precipitation of iron, manganese and aluminum. The water directive Hurdalsvassdraget/Vorma, the municipality of Ullensaker and Risautvalget are interested in figuring out what the source of the metals is and why it happens episodic. It was therefore the starting point for the problems in this thesis, explorations were done in the study area to try and find out what could be the causal links to the fish kills in Risa. To answer the question regarding what led to the fish kills in Risa it was conducted enquiries to map chemical, physical and geological conditions in Upper Risa watershed. Water samples and soil samples were collected in the watershed to investigate the chemistry. Here it was focus on the concentration of metals as iron, aluminum and manganese. It was conducted geophysical measurements with GPR to investigate geological conditions in the area. Other direct methods that was used for this study is sounding, observation wells and grainsize-distribution of soil samples. Modelmuse and ModFlow was used to simulate the groundwater flow, due to the fact that the groundwater can be a source of iron and metals, based on the fact that Risa and Hersjøen is fed by the groundwater reservoir. There has not been found anything that can point to what the cause for the fish kills in Risa is. And it is not possible to conduct any analysis on the gills of the brown trout since the material was not kept. Reasons why further investigation of the fish gills would be interesting is to see if other substances could be found in the fish that is harmful for the trout. And if there were combinations of several parameters that could have led to the fish kills. Its important to keep Risa under surveillance and have follow-ups of the river to pick out major changes that could affect the trout. Vannområdet Hurdalsvassdraget/Vorma (HUVO) M-MINA
- Published
- 2020
30. Kvartærgeologi og grunnvann i Mælingen-området Strekning 4 av Ringeriksbanen og ny E16
- Author
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Pottier, Ingrid Austad, Henriksen, Mona, French, Helen Kristine, and Stormoen, Martin Austin
- Subjects
Geologi - Abstract
Utredninger og planer for Ringeriksbanen startet tidlig på 1990-tallet, og i 2007 begynte prosessen for ny firefelts E16. I en tidlig fase av prøvetakingen ble det oppdaget svært varierende geologiske forhold i dypet på Mælingen-området i Ringerike kommune. Bane NOR ønsker en helhetlig geologisk og hydrogeologisk forståelse av området til bruk under planleggingen og utbyggingen av Ringeriksbanen og ny E16. Datamateriale brukt i oppgaven er 71 totalsonderinger, 14 sylinderprøver og 3 elektriske poretrykksmålinger fra Mælingen-området. Forarbeid og innhenting av datamateriale er utført av rådgivningsgruppen NAA AS, som besto av Norconsult, AAS-Jakobsen og Asplan Viak med underleverandører. Det er supplert med egne georadarundersøkelser og feltarbeid i form av kartlegging av overflateløsmasser, og det er brukt LIDAR-data, flyfoto og satellittbilder. Løsmassemodellen i Leapfrog 3D GEO viser de stratigrafiske lagene i 3D fra Helgelandsmoen over Storelva og Mælingen opp mot Prestmoen. Berggrunnen i området danner en U-dal, grenser i all hovedsak til overliggende morenelag og mektigheten til overliggende sedimenter er på mer enn 140 meter. Lagene over morenelaget veksler mellom siltig leire, siltig sand og sand, og er ifølge scenario 3 avsatt under isavsmeltingen under siste istid. Deltaet i Mælingen-området antas å være dannet i denne perioden, og store deler av deltaet har blitt erodert bort av elver etter siste istid. Det kvartærgeologiske kartet utarbeidet i oppgaven samsvarer i stor grad med eksisterende løsmassekart. Geologisk sett har landskapet blitt lite endret fra 1978 til 2019, og endringene skyldes i all hovedsak menneskelig aktivitet. Grunnvannsmodellen i MODFLOW fra den nordlige delen av Mælingen simulerte at grunnvannsspeilet kan bli hevet og at grunnvannsstrømningene antas ikke å bli påvirket av utbyggingen av Ringeriksbanen og ny E16. En helhetlig geologisk og hydrogeologisk forståelse av Mælingen-området vil være til stor nytte for Bane NOR i byggeprosessen og i valg av byggemetoder. Preparations and planning for the Ringerike Line began early in the 1990s, and in 2007 began the process of making a new E16 highway. In an early phase of the sampling, it was discovered massive variations in the geological conditions in the depth in the area of Mælingen in Ringerike municipality. Bane NOR wants a complete geological and hydrogeological understanding of the area, for use during planning and building the Ringerike Line and a new E16. The data material used in the thesis are 71 total soundings, 14 core samples and 3 electrical piezometers from the area of Mælingen. The engineering company NAA consisting of Norconsult, AAS-Jakobsen and Asplan Viak conducted the pre-work and collection of data material. The data material were supplemented with ground penetrating radar and fieldwork in the form of mapping of surface sediments, and it was also used LIDAR-data, aerial photography and satellite photo. The sediment model in Leapfrog 3D GEO shows the stratigraphic layers in 3D from Helgelandsmoen by Storelva and Mælingen towards Prestmoen. The bedrock in the area forms a U-valley, borders mainly to the overlying moraine and the true thickness to the overlying sediments are more than 140 meters. The stratigraphic layers above the moraine vary between silty clay, silty sand and sand, and according to scenario 3 deposited during the melting of the last ice age. The delta in the Mælingen area is also believed to have been formed in this period, and big parts of the delta were eroded away by rivers after the last ice age. The quaternary geology map created in this thesis correspond to existing sediment maps available. Geologically the landscape has changed little between 1978 and 2019, and the changes that are presented are mainly due to human impact. The groundwater model in MODFLOW from the northern parts of Mælingen simulated that the water table can be raised and that the groundwater flow would not be affected by the development of the Ringerike Line and a new E16. An overall geological and hydrogeological understanding of the area of Mælingen would benefit Bane NOR in the process of construction and in the selection of building methods. M-MINA
- Published
- 2020
31. Espedal-sjøfasen under siste isavsmelting
- Author
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Bjordal, Ingeborg, Henriksen, Mona, and Jakobsen, Leif Vidar
- Subjects
Kvartærgeologi ,LiDAR ,Skåbu ,Georadar ,Matematikk og Naturvitenskap: 400 [VDP] - Abstract
I denne oppgaven er det brukt LiDAR data og georadarundersøkelse til å få innblikk i utviklingen i nordlige Espedalen under siste isavsmelting. Dette er gjort ved undersøkelse av to deltaavsetninger ved innsjøene Olstappen og Slangen, ved Skåbu i Nord-Fron kommune. Georadarundersøkelsene har gitt innblikk i oppbygning og dreneringsretninger i noen av deltaflatene, mens LiDAR undersøkelsen har gitt innblikk i dreneringsretninger ved kartlegging av deltaenes overflater. Kartleggingen som er gjort tyder på en generell dreneringsretning mot nordvest på vestsiden av Vinstra og mot nordøst på østsiden av Vinstra, samt mot nordøst ved Slangen. Ut ifra kartleggingen er det sett tegn som tyder på at det har vært en stor sammenhengende innsjø i området, som har blitt senket i tre omganger før dagens vannivå. I tillegg er det funnet tegn på høydenivåer før isen var smeltet bort i Olstappen og Slangens daler. Resultatene fra denne kartleggingen er i godt samsvar med tidligere undersøkelser i dette området. In this study, LiDAR-data and a georadar survey has been used to gain insight into the development in northern Espedalen during the last deglaciation. This was done by examining two delta deposits at the lakes Olstappen and Slangen, by Skåbu in Nord-Fron municipality. The georadar survey have provided insight into the structure and drainage directions in some of the delta surfaces, while the LiDAR survey has provided insight into drainage directions by mapping the deltas' surfaces. The mapping indicates a general drainage direction to the northwest on the west side of Vinstra and to the northeast on the east side of Vinstra, as well as to the northeast by the lake Slangen. From the mapping, there are found signs that there has been a large continuous lake in the area, which has been lowered in three steps before today's water level. In addition, signs of altitudes were found that can indicate levels before the ice had melted away in the Olstappen and the Slangen valleys. The results of this survey are in good agreement with previous studies from this area. M-LUN
- Published
- 2020
32. Carbon stock and geological development of a peatland in Karlshaugen nature reserve
- Author
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Sklet, Vera, Henriksen, Mona, Strand, Line Tau, and Nygaard, Per Holm
- Subjects
Karlshaugen ,Peatlands - Abstract
Carbon stocks of peatlands is of growing interest due to the ability to store large amounts of carbon. To provide data of this subject this master thesis presents results from a study of a peatland within a forest nature reserve outside of Oslo, Norway. First, peat volume was estimated using a combination of ground penetrating radar survey and GIS tools (EkkoPulse software, ArcMap and Excel). Second, sediment cores retrieved from the peat were analysed in the laboratory to analyse the bulk density and carbon content of the organic material and to calculate the carbon stock of the peatland. The data were also used to explain how this peatland has developed. The volume of the total peatland analysed by the ground penetrating radar was calculated to be 6487 m3. Degree of decomposition, described by the von Post scale, shows similar trends for all four cores; it is low in the shallow peat and increases with depth where they stabilize at level 6-8. Using Loss On Ignition as total amount of organic material gave values well above 90%, except for the samples that visibly contain minerogenic material. These results were consistent with results from total carbon analysis using LECO Truspec instrument finding total carbon content of peat core MM1to be 47-55%. The total carbon content of the remaining three cores were determined by regression analysis to be 50-53% in core MM2, 5154% in core MM3 and 52-54% in core MM4. Carbon stocks in MM1 range from 2 kgC/m2 to 7 kgC/m2. The total amount of carbon stored in this peatland is calculated to be 278 ton. For the top meter the carbon stock is 41.1 kg/m2. The hypothesis for the formation of this peatland being a depression in bedrock filled with water to form a pond, later filled with sediments and organic material was supported by the shape of the peat basin illustrated in the GPR survey, and the fine minerogenic material in the bottom part of peat core MM1. Further field observations support peatland boundary is changing, and it can be predicted that the rise in temperature and changes in precipitation might cause degradation of organic material in the peatland. This process may be part of a positive feedback loop with climate change. Karbonlager i myr er av økende interesse grunnet deres evne til å lagre store mengder karbon. For å belyse dette temaet presenterer denne oppgaven resultater fra en studie av en myr i Karlshaugen naturreservat i Nordmarka, Oslo. Volum av myra ble kartlagt ved en kombinasjon av georadar og GIS-verktøy (EkkoPuls-programvare, ArcMap og Excel). Videre ble fire sediment kjerner hentet opp fra myra, og analysert for tetthet og karboninnhold. Dette er brukt til å estimere mengde karbon lagret i myra. Basert på data fra undersøkelsen er det også utformet en forklaring på hvordan denne myra er dannet og har utviklet seg. Volumet av den delen av myra som er kartlagt med georadar er estimert til 6487 m3. Grad av nedbrytning i materialet, beskrevet ved hjelp an von Post skalaen, viser lignende utvikling i de fire kjernene. I det grunne myrmaterialet er det en lav grad av nedbrytning, mens den øker i dybden, og stabiliserer seg på nivå 6-8. Ved bruk av glødetap er mengde organisk materiale i prøvene bestemt, dette ga resultater på godt over 90%, bortsett fra de prøvene som inneholdt mineralsk materiale. Disse resultatene samsvarer med analysene for karbon innhold gjennomført ved bruk av LECO Truspec instrument. Disse viser karboninnhold på 47-55% for kjerne MM1. Karbon innholdet i de resterende kjernene er bestemt med en regresjonsanalyse, som ga resultater på 50-53% for kjerne MM2, 51-54% for kjerne MM3 og 52-54% for kjerne MM4. Karbonlager utregninger for kjerne MM1 variere fra 2 kgC/m2 til 7kgC/m2. Den totale mengden karbon lagret i denne myra er estimert til 278 tonn. For den øverste meteren i myra er karbonlageret beregnet til 41.1 kg/m2. Hypotesen for hvordan denne myra er dannet går ut på at en nedsenkning i grunnfjellet ble fylt med vann og dannet et tjern, som senere ble fylt med sedimenter og organisk materiale. Denne hypotesen er støttet av formen på myrbassenget som er godt illustrert i georadar undersøkelsen, og funn av mineral materiale i bunnen av den dypeste myrkjernen. Videre så støtter feltobservasjoner tidligere resultater om at denne myra er i endring, det kan antas at økning i temperatur og ening i nedbør kan føre til nedbrytning at organisk materiale og utslipp av karbon. Denne prosessen kan være en del av en positiv tilbakekoblingsmekanisme med globale klimaendringer. M-MINA
- Published
- 2019
33. Application of waterborne electrical resistivity tomography and ground penetrating radar in the delta area of Numedalslågen, Norway
- Author
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Øybekk, Vilde Jørdre, Henriksen, Mona, and Scheibz, Jürgen
- Subjects
Sediments ,GPR ,Electrical Resistivity Tomography ,Numedalslågen ,ERT ,Ground Penetrating Radar - Abstract
Two non-invasive geophysical methods have been tested in the lowermost reaches of the river Numedalslågen, Southern Norway. The aim were to estimate thickness of sediments, possible layering and the depth to the bedrock. Waterborne electrical resistivity tomography (ERT) measurements were conducted in brackish water above the delta. Several lines of ERT data were collected by towing an electrode streamer by boat. The data were processed in RES2DINV. Processing of the ERT data gave resistivity values mainly ranging from approximately 20 to 60 Ωm. This can be interpreted as clay rich sediments, when seen in context of the settings and knowledge about the geomorphology of the area. However, challenging conditions during the survey gave data and results that were difficult to interpret further. One standard resistivity value for the water body based on conductivity measurements and editing of the data to include bathymetry data were tried to improve the results. Nevertheless, few measured data points compared to a high number of model blocks, high RMS errors and vertical rather than horizontal sections in the processed data gave little confidence in the results.Ground penetrating radar (GPR) data were collected along three profiles at a beach in the SE end of the delta. Antennas of 50 megahertz were used to map deposits and subsurface structures, resulting in GPR profiles with reflections mainly interpreted as sand and a maximum penetration depth of 20 meters. Reflection free parts were interpreted as clay rich sediments or sediments with brackish groundwater. Despite challenges with processing of data and interpretation of results, the methods should be considered suitable for the target of the study. The settings were demanding, especially for the ERT, and this is reflected in the results. To ikke-invasive geofysiske metoder har blitt testet i og langs utløpet til Numedalslågen, sør i Norge. Målet var å estimere mektighet av sedimentene, mulige lagdelinger og dybde til fjell. Vannbåren Elektrisk Resistivitets Tomografi målinger ble utført i brakkvannet over deltaet. Flere linjer med ERT data ble samlet inn ved at en elektrodekabel ble tauet med båt. Dataene ble prosessert i RES2DINV. Prosessering av ERT dataene ga i hovedsak resistivitetsverdier mellom 20 og 60 Ωm. Dette kan tolkes som at sedimentene er rike på leire, særlig sett i sammenheng med området og dets geologiske utvikling. Utfordrende forhold under feltarbeidet gjorde det derimot vanskelig å tolke data og resultater videre. Forsøk på å forbedre dataene ble gjort, som ved å for eksempel å sette en resistivitetsverdi som standard for vannet og endre redigering av batymetridata. Likevel gav prosesseringen lite pålitelige resultater. Georadardata ble samlet inn langs tre profiler på stranda i SØ-retning for deltaet. 50 megahertz-antenner ble brukt i forsøket på å kartlegge løsmasser og strukturer under overflaten. Det resulterte i georadarprofiler med refleksjoner som i hovedsak ble tolket som sand. Signalet fra georadaren nådde dyp på maksimum 20 meter. Refleksjonsfrie områder ble tolket som sedimenter rike på leire eller med innhold av brakt grunnvann. På tross av utfordringer med prosessering av data og tolkning av resultatene, bør metodene anses som passende for studiets mål. Krevende forhold, særlig under innsamlingen av ERT data, er reflektert i resultatene. M-MINA
- Published
- 2018
34. Soil carbon and glacifluvial deposits in the deglaciation landscape of Gausdal Vestfjell
- Author
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Bøe, Lina, Henriksen, Mona, and Strand, Line Tau
- Subjects
Norwegian Forest Podzol ,Soil Carbon Stabilisation ,Parent Material ,Glacifluvial deposition - Abstract
Glacifluvial deposits and their soil carbon stock and stability have been studied in the deglaciation landscape of Gausdal Vestfjell, Norway. Soil profiles are described and sampled for parent material clast analysis, density calculation and soil chemical analysis across a variety of glacifluvial landforms deposited in both flowing and stagnant ice, subaerially as well as subaqueously. The landforms include eskers, kame, kame terraces, delta and fan deposits. The morphology and sedimentology of 17 landforms are described and interpreted from remote sensing and field investigation. Methods have included visualization of LiDAR data in ArcMap, stratigraphic logging, sediment property analysis and Ground Penetrating Radar measurements. Calculation of carbon stock is based on soil density, stone and boulder content, horizon thickness and laboratory measurements of total carbon content. Gausdal Vestfjell was deglaciated by down-wasting of stagnant ice, where kame terraces at the highest elevations (820-890 masl) record a progressive lowering of the ice surface. Fan, delta and sandur deposits record ice-damming and gradual drainage of meltwater from the lowest elevations (778-810 masl). The glacifluvial deposits are subangular, sorted and mainly composed of sand and gravel although both finer and coarser sediments occur. The deposits are dominated by tabular and through cross bedding, current ripples and horizontal lamination, erosive surfaces and variable discharge mainly in the upper flow regime. The carbon stocks can be linked to depositional environments and processes during deglaciation. Early and late stage deposition at high (~890 masl) and low elevation (~790 masl), respectively, resulted in low carbon stocks, while deposition in stagnating ice at intermediate elevations is linked to high carbon stocks (~850 masl). The coarse texture of the deposits limits carbon input, decomposition, translocation and stabilisation due to low total particle surface area and water and nutrient retention capacity. Soil texture further exerts a major influence on carbon stocks through organic material occlusion and complexation with minerals, and a doubling of the silt and clay content from 20 % to 40 % nearly triples carbon stock. The texture varies greatly due to large variations between and within depositional environments and processes, and the glacifluvial carbon stocks are thus linked to the formation of the landforms they are found on. The carbon stock of the soils is estimated down through the Bs horizon, and ranges from ~ 3 to 18 kg/m2, with a mean estimated to 7.99 kg/m2. The fraction stored in the mineral soil is highly variable and ranges from ~10 % to ~ 100 %, averaging at 63 %. Soil organic carbon varies with the nutrition status of the nearby bedrock and parent material, the degree of soil formation and the nature of sediment transport and deposition. The degree of soil formation is higher in soils formed from innutritious parent material. The soil carbon stock is higher in soil formed on landforms composed of immature sediment, deposited in the lower flow regime and with a low relief with the surrounding landscape. Stabilisation of organic carbon in the mineral soil depends on the presence of clay minerals in the parent material and soil weathering products including iron and aluminium oxides and phyllosilicates. Mineral-stabilised carbon in soil of nutritious parent material may show higher chemical recalcitrance, while carbon stabilised in more acidic soils formed from less nutritious parent material may be more labile and to a larger degree stabilised by oxides. Upscaling of carbon stock estimates from the detailed study of selected landforms was done by georeferencing a bedrock map and a topographic map based on LiDAR data to all landforms mapped by remote sensing in the study area (c. 500). Parent material nutrition status can be inferred from the local bedrock, and the nature of deposition from the shape of landforms and their relationship with the surrounding landscape. The small number of deposits studied provides no statistical significance for extrapolation, however, the trends and variation in the carbon stocks of glacifluvial soils appear to be predictable. By upscaling, the organic horizon carbon stocks of the glacifluvial soils were estimated to be equivalent to ~121 Mg CO2/ha, and the carbon stocks of the mineral soil horizons to ~ 241 Mg CO2/ha. The former is unstable and may be lost from the deglaciation landscape to the atmosphere in a warmer climate while the latter may be lost if there is a change in land use. Overall, the landforms show large carbon stock variations for both organic and mineral soil horizons. Calculated values are comparable to values obtained in previous studies for carbon stocks of forest soils in mountainous ecosystems. Glasifluviale avsetninger og deres karbonlager er studert i isavsmeltingslandskapet i Gausdal Vestfjell, Oppland. Jordprofiler fra fire glasifluviale landformer er beskrevet, og det er tatt prøver for analyse av opphavsmateriale, jordtetthet og jordkjemiske egenskaper fra tolv landformer. Morfologien og sedimentologien til i alt 17 landformer, inkludert eskere, kame, kameterrasse, delta og vifteavsetninger er beskrevet og tolket basert på fjernanalyse og feltundersøkelse, blant annet ved fremstilling av LiDAR-data i Arc MAP, stratigrafisk logging, analyse av sedimentegenskaper og geroradarmålinger. Beregning av karbonlager er basert på jordtetthet, innhold av stein og blokk, sjikttykkelse, og laboratorieanalyse av jordas innhold av total karbon. M-MINA
- Published
- 2018
35. Sen weichsel isdynamikk og isavsmeltingsmønster av Den fennoskandiske innlandsisen i Gausdal Vestfjell, sentrale Sør-Norge, basert på romlige data
- Author
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Putniņš, Artūrs, Henriksen, Mona, Tveite, Håvard, and Landvik, Jon Y.
- Subjects
Mathematics and natural science: 400::Geosciences: 450 [VDP] - Abstract
Evidence-based geomorphological research (analyses of glacial landform record) is one of the commonly used types of glacial reconstructions applied for studying the past ice sheets. The work covered by this thesis contains a geomorphological data set of more than 17 000 glacial and glacifluvial landforms in Gausdal Vestfjell, south-central Norway. The study area is located in an inner region of the former Fennoscandian Ice Sheet (FIS) and contains a palaeogeological record on the flow pattern evolution and retreat during the Late Weichselian. The geomorphological mapping was carried out by exploiting the accessibility of high resolution LiDAR (Light Detection And Ranging) data and the capabilities provided by the latest advances in Geographical Information System (GIS) technologies such as terrain visualisations in an interactive 3D environment. A consequence of the ‘age of LiDAR’ is the increase in the resolution of the findings with more and smaller-sized landforms being mapped, that earlier were likely to be left out as unrecognised. These small-sized landforms may provide information on relatively short-lived events representing changes of glacial dynamics. This is particularly the case when such landforms are found overlapping other larger landforms. The mapping results have been validated by field observations. Since the manual mapping of landforms is a time consuming and potentially subjective process, part of the thesis explores the semi-automated mapping (SAM) techniques that may be a reliable and effective alternative for data extraction. Several SAM methods are proposed for glacial streamlined landform extraction, yet none was considered optimal for the extraction of glacial ice flow directions in a complex terrain, such as the study area in the Scandinavian Mountains. Therefore, the potential of the grayscale thinning (skeletonisation) application for the extraction of directional trends from the terrains is explored. The meltwater landform domain is a valuable source of information on the dynamics of past ice sheets and their deglaciation. Possibly due to the uncertainties in establishing the correlations of spatial and temporal relations of (and, in particular, the marginal) meltwater landforms it has often had only a secondary role. Here, GIS tools were used to introduce a simple reference surface gradient and apply a vertical adjustment of the ‘virtual ice surface’ representing vertical down-wasting of ice in order to increase the credibility of meltwater landform correlations. This enabled to distinguish several important ice marginal positions and to reconstruct the significant events of deglaciation in a greater detail. The study reveals a stepwise evolution of the FIS flow pattern during the Late Weichselian where a topography independent ice flow (Phase I) is followed by a regional (Phase II) that is subsequently replaced by a strongly channelized, topography-driven ice flow (Phase III with several substages). Prior to the ice disintegration, the ice flow was increasingly confined into valleys, likely separated by colder, less active ice. The deglaciation is characterised by a vertical down-melting of ice, dynamic evolution of the meltwater drainage systems that included temporary ice-dammed lakes and spillways, and deposition of various glacifluvial landforms. Although the presented work can be considered as a local study from Gausdal Vestfjell, it improves our knowledge on the evolution and retreat of the FIS. Further, the proposed methods may find useful applications in other glacial geomorphology studies elsewhere. Bevisbaserte geomorfologiske undersøkelser (analyser av glasiale landformer) er en av de vanligste måtene å rekonstruere tidligere innlandsiser. Arbeidet som omfattes av denne avhandlingen inneholder et geomorfologisk datasett med mer enn 17 000 glasiale og glasifluviale landformer i Gausdal Vestfjell, midtre Sør-Norge. Studieområdet ligger i indre region av Den fennoskandiske innlandsisen (FIS) og inneholder et verdifullt geologisk arkiv om utviklingen av strømningsmønsteret og isavsmeltingen i sein weichsel. Geomorfologisk kartlegging ble utført ved å utnytte tilgjengeligheten av høyoppløselig LiDAR-data (Light Detection And Ranging) og å anvende de nyeste teknologiske framskrittene innen geografiske informasjonssystemer (GIS) som interaktive 3Dvisualiseringer av terrenget. En konsekvens av denne ‘LiDAR-epoken’ er høyere oppløsning av kartleggingsfunnene med forekomst av langt flere og mindre landformer som sannsynligvis ville blitt oversett tidligere. Disse små-skala landformene kan gi informasjon om relativt kortvarige hendelser som representerer endringer i isdynamikken. Dette gjelder spesielt når slike landformer er funnet oppå andre større landformer. Kartleggingsresultatene er stadfestet med feltobservasjoner. Pierādījumos balstītie ģeomorfoloģiskie pētījumi (glaciālo reljefa formu analīze) ir viens no biežāk pielietotajiem rekonstruckiju veidiem pagātnes ledusvairogu pētījumos. Doktora disertācijas ietvaros veiktais pētījums sevī ietver informāciju par vairāk kā 17 tūkstošiem dažādu glacigēno un ledāja kušanas ūdeņu reljefa formām no Gausdālas Vestfjelas (Gausdal Vestfjell) apkārtnes, centrālajā Dienvidnorvēģijā. Pētījuma teritorija atrodas bijušā Fenoskandijas ledusvairoga centrālā apgabala iecirknī, un tājā ir atrodamas vērtīgas paleoģeoloģiskās liecības par apledojuma plūsmu attīstību vēlā Vislas apledojuma laikā un ledusvairoga kušanu leduslaikmeta beigu posmā. Ģeomorfoloģiskā kartēšana tika veikta izmantojot augstas izšķirtspējas LiDAR (lāzerskenēšanas) datu pieejamību un Ģeogrāfisko Informācijas Sistēmu (ĢIS) sniegtās iespējas, kā piemēram, reljefa vizualizāciju interaktīvajā 3-dimensiju vidē. Likumsakarīgi, ka LiDAR laikmets ir atnesis izšķirtspējas pieaugumu, kā rezultātā ir iespējams kartēt un datu kopā ietvert vairāk un izmēros mazākas reljefa formas, kuras agrāk būtu palikušas nepamanītas. Šīs mazizmēra reljefa formas iespējams var sniegt ieskatu relatīvi īslaicīgos notikumos ledus plūsmu dinamikas attīstībā. Tas jo īpaši ir attiecināms gadījumos, kad šīs mazizmēra reljefa formas ir atrodamas pārklājamies uz citām, lielākām reljefa formām. Pētījuma ietvaros iegūtie kartēšanas rezultāti ir apstiprināti ar lauka darbos gūtajiem novērojumiem. Tā kā manuāla reljefa formu kartēšana ir laikiepiltīgs un potenciāli subjektīvs process, daļa no doktora disertācijā ietvertā pētījuma apskata (semi-)automātiskās kartēšanas metodžu pielietošanu kā potenciāli uzticamu un efektīvu alternatīvu datu ieguvei. Kaut arī pastāv dažas reljefa formu automātiskās atpazīšanas metodes, neviena no esošajām metodēm nav uzskatāma par piemērotu datu par ledus plūsmu virzieniem ieguvei sarežģītos reljefa apstākļos, kādi ir satopami pētījuma teritorijā, Skandināvijas kalnu grēdas centrālajā apgabalā. Tāpēc pelēktoņu (grayscale) retināšanas rīkā balstīta reljefa virzienu noteikšanas metode, tiek apskatīta kā alternatīva esošajām metodēm. Ledājkušanas ūdeņu reljefa formas sevī ietver vērtīgu informācijas avotu par ledusvairogu plūsmas dinamiku un to atkāpšanos leduslaikmeta beigu posmā. Taču, iespējams tieši neskaidrību un problemātikas dēļ, kāda pastāv saistībā ar ledāja kušanas reljefa formu (un jo īpaši marginālo) korelāciju izveidošanu, ledājkušanas ūdeņu reljefa formām bieži ir bijusi tikai otršķirīga nozīme. Šī darba ietvaros tika pielietoti ĢIS rīki, lai ieviestu vienkāršotu atsauces virsmu - ‘virtuālo ledāja virsmu’, ar mērķi uzlabot marginālo ledājkušanas ūdeņu reljefa formu korelācijas. Šādas atskaites virsmas ieviešana ir veicinājusi ledāja marginālo pozīciju noteikšanu un galciālo rekonstrukciju izveidi daudz augstākā detaizācijas pakāpē kā līdz šim. Veiktais pētījums atklāj pakāpeniskumu Fenoskandijas ledusvairoga ledus plūsmu dinamiskas attīstībā vēlā Vislas apledojuma laikā, kur no topogrāfiski neatkarīgas plūsmas (fāze I) tā pāriet reģionālā (fāze II) ar zināmu zemledāja topogrāfijas ietekmi, līdz tā iegūst izteiktu kanālveida (fāze III un tās paveidi) raksturu. Pirms ledusvairoga aprimšanas, ledus plūsma pakāpeniski tika arvien vairāk novirzīta ielejās, starp tām valdot stagnata un aprimuša ledus apstākļiem. Deglaciāciju galvenokārt raksturo ledus biezuma pakāpeniska samazināšanās un dinamiska ledājkušanas ūdeņu sistēmu attīstību, kura ietver īslaicīgu ledājkušanas ūdeņu baseinu, ledājkušanas ūdeņu pārteces kanālu eksistenci kā arī akumulatīvo ledājkušanas ūdeņu reljefa formu veidošanos. Kaut arī šis pētījums ir raksturojams kā lokālas nozīmes pētījums Gausdālas Vestfjelas apkārtnei, tas sniedz nozīmīgu papildinājumu mūsu zināšanās par Fenoskandijas ledusvairoga attīstību un deglacācijas gaitu. Turklāt, šī darba ietvaros piedāvātās metodes ir potenciāli pielietojamas glaciālās ģeomorfoloģijas pētījumos citviet seno apledojumu skartajās teritorijās.
- Published
- 2018
36. Landforms and processes in the catchment of lake Årungen
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Samuelsen, Tonje and Henriksen, Mona
- Subjects
Landformer ,Matematikk og Naturvitenskap: 400 [VDP] ,Årungen ,Løsmasser - Abstract
I dette studiet er pågående og tidligere prosesser og hendelser i nedbørsfeltet til Årungen undersøkt og analysert ved geomorfologisk kartlegging av landformene ved bruk av LiDAR-data. Feltundersøkelse ved bruk av georadar og sedimentologisk logging er tatt i bruk for å få et innblikk i prosessene som har hendt i studieområdet. Den geomorfologiske kartleggingen viser at landformene hovedsakelig er dannet av glasiale- og fluviale prosesser, der fluviale prosesser står for pågående prosesser i dag. Kartlegging tyder på at lineamenter i studieområdet er bestemmende for dreneringssystemet og beliggenhet av elve- og bekkeløp. Høydedrag, løsmasser og orientering av morenerygger vil antageligvis ha en styrende rolle for avrenningssystemet. Modellene gir en indikasjon på at studieområdet er preget av tidligere havnivå og havnivåendringer, der sedimentasjon av materiale er bestemmende for synlige ryggformer og nedskjæringer i løsmasser. In this study, ongoing and previous processes and events in the catchment of lake Årungen have been investigated and analyzed by geomorphological mapping of landforms using LiDAR-data. Field techniques including Ground Penetrating Radar, sedimentological mapping and analysis provide an insight to the processes that have taken place in the study area. The geomorphological mapping of landforms indicate that the landforms are mainly formed by glacial and fluvial processes. Mapping indicates that fluvial processes in the study area is one of the main ongoing processes today. Also, mapping indicates that lineaments in the study area are determining for the drainage system and location of streams and rivers. Elevations, debris and orientation of moraine ridges will presumably have a controlling role of the drainage system. The models indicate that the study area is affected by earlier sea level and sea level changes, where sedimentation of debris determines visible ridges and channels. M-LUN
- Published
- 2017
37. The formation and distribution of aeolian sand dunes at Aurmoen in the Gardermoen area
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Flatla, Marte, Henriksen, Mona, and Jakobsen, Leif Vidar
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paleovindretning ,sanddyne ,Aurmoen ,inland dune field ,sand ,isavsmelting ,Flygesand ,geologi ,Hauerseter ,Flygesanddyner ,Vindavsetninger ,eolisk ,Gardermoen ,Mathematics and natural science: 400::Geosciences: 450::Quaternary geology, glaciology: 465 [VDP] - Abstract
Aurmoen sanddynefelt er et av de største flygesandfeltene i innlandet i Norge, og er tilknyttet de store breelvavsetningene i Gardermoområdet. Eoliske avsetninger (vindavsetninger), særlig i form av flygesandområder, er en relativt sjelden landform i Norge og er lite undersøkt. Det er gjort få detaljstudier av slike eoliske sanddyner, blant annet når det gjelder absolutte dateringer, oppbygning av dynefeltene og tolkning av paleovindregime. I dette studiet har fjernanalytiske data (LiDAR-data) og feltundersøkelser ved bruk av georadar og sedimentologiske analyser gitt et innblikk i flygesandfeltets oppbygning og utbredelse på Aurmoen. Sanddynenes form er hovedsakelig av parabolsk karakter, samt at en rekke langitudinale og transverse dyner har blitt kartlagt. Oppbygningen av de parabolske dynene gir antydning til en todelt paleovindretning under dannelsen av flygesandfeltet. Dette innebærer en tilsynelatende paleovindretning fra nord-nordvest i den vestlige delen, og fra nord i den østlige delen av feltet. Sanddynene antas å ha blitt dannet i løpet av 150 – 200 år, innenfor tidsrommet 10,8 – 10,4 kal. ka før nåtid. Dette innebærer perioden etter området ble isfritt og breelvsedimentene ble avsatt som et delta. På denne tiden kunne vinden fra den nærliggende innlandsisen i nord kunne erodere i breelvmaterialet, før vegetasjonen ble etablert for fullt og stabiliserte sanddynene. The Aurmoen dune field is one of the largest inland dune fields in Norway, and is associated with a large glaciofluvial deposit in the Gardermoen area, South Eastern Norway. Aeolian deposits (wind deposits), especially in terms of aeolian dune fields, is a relatively rare landform in Norway and is poorly investigated. Regarding e.g. absolute dating, the formation of dune fields, and interpretation of paleo wind regimes, very few detailed studies of such sand dunes have been conducted. In this study, remote analytical (LiDAR-) data and field techniques including Ground Penetrating Radar (GPR) and sedimentological analysis provides an insight into the Aurmoen aeolian dune field’s formation and distribution. The different sand dunes are mainly parabolic, as well as a number of longitudinal and transverse ridges. The structure of the parabolic dunes may suggest two different paleo wind directions during the main dune-building event. This implies an apparent wind direction from north-northwest in the western part of the dune field, and from the north in the eastern part. The dunes are believed to have formed during a period of 150 – 200 years, around 10.8 to 10.4 cal. ka BP. This involves the period after the area was deglaciated and the glaciofluvial material was deposited as a delta. At this point, the wind from the ice sheet in the north was able to erode in the glaciofluvial material, before the vegetation became fully established and stabilized the dunes. M-MINA
- Published
- 2016
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