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- Goodfellow, Bradley W., 1971-
(författare)
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Relict non-glacial surfaces and autochthonous blockfields in the northern Swedish mountains
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Relict non-glacial surfaces occur in many formerly glaciated landscapes, where they represent areas that have escaped significant glacial modification. Frequently distinguished by blockfield mantles, relict non-glacial surfaces are important archives of long-term weathering and landscape evolution processes. The aim of this thesis is to examine the distribution, weathering, ages, and formation of relict non-glacial surfaces in the northern Swedish mountains. Mapping of surfaces from aerial photographs and analysis in a GIS revealed five types of relict non-glacial surfaces that reflect differences in surface process types or rates according to elevation, gradient, and bedrock lithology. Clast characteristics and fine matrix granulometry, chemistry, and mineralogy reveal minimal chemical weathering of the blockfields. Terrestrial cosmogenic nuclides were measured in quartz samples from two blockfield-mantled summits and a numerical ice sheet model was applied to account for periods of surface burial beneath ice sheets and nuclide production rate changes attributable to glacial isostasy. Total surface histories for each summit are almost certainly, but not unequivocally, confined to the Quaternary. Maximum modelled erosion rates are as low as 4.0 mm/kyr, which is likely to be near the low extreme for relict non-glacial surfaces in this landscape. The blockfields of the northern Swedish mountains are Quaternary features formed through subsurface physical weathering processes. While there is no need to appeal to Neogene chemical weathering to explain blockfield origins, these surfaces have remained continuously regolith-mantled and non-glacial since their inception. Polygenetic surface histories are therefore indicated, where the large-scale surface morphologies are potentially older than their regolith mantles.
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| 2. |
- Margold, Martin, 1981-
(författare)
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Retreat pattern and dynamics of glaciers and ice sheets: reconstructions based on meltwater features
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Glaciers and ice sheets covered extensive areas in the Northern Hemisphere during the last glacial period. Subsequently to the Last Glacial Maximum (LGM), they retreated rapidly and, except for Greenland and some other ice caps and glaciers, they vanished after the last glacial termination. This thesis examines the dynamics of deglacial environments by analysing the glacial geomorphological record with focus on the landforms created by glacial meltwater. The aims are (i) to evaluate the data available for mapping glacial meltwater features at the regional scale, and (ii) to demonstrate the potential of such features for regional ice retreat reconstructions in high-relief landscapes. Meltwater landforms such as ice-marginal meltwater channels, eskers, deltas and fossil glacial lake shorelines are used to infer former ice surface slope directions and successive positions of retreating ice margins. Evaluated high-resolution satellite imagery and digital elevation models reveal their potential to replace aerial photographs as the primary data for mapping glacial meltwater landforms. Following a methods study, reconstructions of the deglacial dynamics are carried out for central Transbaikalia, Siberia, Russia, and for the Cordilleran Ice Sheet (CIS) in central British Columbia, Canada, using regional geomorphological mapping surveys. Mapped glacial landforms in central Transbaikalia show evidence of a significant glaciation that possibly extended beyond the high mountain areas. Large glacial lakes were formed as advancing glaciers blocked rivers, and of these, Glacial Lake Vitim was the most prominent. Deglacial dynamics of the CIS reveals that the ice divide shifted to the Coast Mountains in north-central British Columbia and the eastern ice margin retreated towards the ice divide in late glacial time. This thesis demonstrates the potential to reconstruct ice retreat patterns and deglacial dynamics at regional scales by interpretation of the meltwater landform record.
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| 3. |
- Ivehammar, Pernilla, 1971-
(författare)
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How to deal with the encroachment costs in road investment CBA
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- An important basis for decisions regarding road investments is Cost Benefit Analysis (CBA), where all costs and benefits should be taken into account and expressed in monetary terms. A valuation of the cost for the encroachment caused by a new road in, for example, a recreation area or a residential area is, however, missing in road investment CBA. The purpose of this thesis is to develop approaches to deal with the encroachment costs. More specifically two approaches are developed.One approach is ”cost transfer” for typical cases. With this approach the encroachment cost is estimated ex post for a number of existing roads within each typical case. The results are to be used to estimate a calculation formula to use for CBA of planned road investments where the encroachment can be referred to a particular typical case. The typical case ”barrier to water” was chosen for a pilot study with the aim of developing the method for data collection, and study what is most important for the encroachment cost per affected individual.The other approach is a method, developed in the thesis, for estimating the encroachment cost ex ante for each specific object. The method is called COPATS, ”Combined Opinion Poll and Travel Survey”. It makes use of the fact that roads mean both positive and negative effects to a different degree for the affected people. Data of the residence location, visiting frequency in the encroachment area and travel pattern is collected by a postal questionnaire before deciding on a road investment. In the same questionnaire it is also asked whether the respondent is for or against the planned road. The encroachment cost can be estimated from the respondents´ balancing of the benefit of travel time savings, and possibly some other positive effects, against the negative encroachment caused by the planned road.A conclusion is that both alternatives seem to be possible ways of including encroachment costs as part of road investment CBA. To estimate calculation formulas for cost transfer in some common typical cases, a large number of further encroachment cost studies must though be made. COPATS is closer to practical application, but needs to be further developed in collaboration with road planners.
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