| 1. |
- Fredin, Ola
(författare)
-
Glacial inception and Quaternary mountain glaciations in Fennoscandia
- 2002
-
Ingår i: Quaternary International. - 1040-6182 .- 1873-4553. ; 95-96, s. 99-112
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this review is twofold. First, the role of the Fennoscandian mountains as a nucleation center for glacial inception is investigated. The second objective is to review glacial erosion by mountain glaciers throughout the Quaternary. All available field data and several modelling experiments show that the Fennoscandian mountains seeded the last glaciation. Since the mountains seem to be of key importance for ice-sheet inception, it is reasonable to assume a similar inception pattern throughout most of the major Pleistocene glaciations. This pattern also implies prolonged periods of glacial ice in the Fennoscandian mountains during late Cenozoic time. Mountain-based glaciers thus have had a long time to act on their substratum resulting in a profound geomorphological impact.
|
|
| 2. |
- Fredin, Ola, 1972-
(författare)
-
Mountain centered icefields in northern Scandinavia
- 2004
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mountain centered glaciers have played a major role throughout the last three million years in the Scandinavian mountains. The climatic extremes, like the present warm interglacial or cold glacial maxima, are very short-lived compared to the periods of intermediate climate conditions, characterized by the persistence of mountain based glaciers and ice fields of regional size. These have persisted in the Scandinavian mountains for about 65% of the Quaternary. Mountain based glaciers thus had a profound impact on large-scale geomorphology, which is manifested in large-scale glacial landforms such as fjords, glacial lakes and U-shaped valleys in and close to the mountain range.Through a mapping of glacial landforms in the northern Scandinavian mountain range, in particular a striking set of lateral moraines, this thesis offers new insights into Weichselian stages predating the last glacial maximum. The aerial photograph mapping and field evidence yield evidence that these lateral moraines were overridden by glacier ice subsequent to their formation. The lateral moraines were dated using terrestrial cosmogenic nuclide techniques. Although the terrestrial cosmogenic nuclide signature of the moraines is inconclusive, an early Weichselian age is tentatively suggested through correlations with other landforms and stratigraphical archives in the region. The abundance and coherent spatial pattern of the lateral moraines also allow a spatial reconstruction of this ice field. The ice field was controlled by topography and had nunataks protruding also where it was thickest close to the elevation axis of the Scandinavian mountain range. Outlet glaciers discharged into the Norwegian fjords and major valleys in Sweden.The process by which mountain based glaciers grow into an ice sheet is a matter of debate. In this thesis, a feedback mechanism between debris on the ice surface and ice sheet growth is presented. In essence, the growth of glaciers and ice sheets may be accelerated by an abundance of debris in their ablation areas. This may occur when the debris cover on the glacier surface inhibits ablation, effectively increasing the glaciers mass balance. It is thus possible that a dirty ablation area may cause the glacier to advance further than a clean glacier under similar conditions. An ice free period of significant length allows soil production through weathering, frost shattering, and slope processes. As glaciers advance through this assemblage of sediments, significant amounts of debris end up on the surface due to both mass wastage and subglacial entrainment. Evidence that this chain of events may occur, is given by large expanses of hummocky moraine (local name Veiki moraine) in the northern Swedish lowlands. Because the Veiki moraine has been correlated with the first Weichselian advance following the Eemian, it implies a heavily debris charged ice sheet emanating from the mountain range and terminating in a stagnant fashion in the lowlands.
|
|
| 3. |
|
|
| 4. |
- Fredin, Ola, et al.
(författare)
-
Relict lateral moraines in northern Sweden : evidence for an early mountain centered ice sheet
- 2002
-
Ingår i: Sedimentary Geology. - 0037-0738 .- 1879-0968. ; 149:1-3, s. 145-156
-
Tidskriftsartikel (refereegranskat)abstract
- Glacial geomorphology along the eastern rim of the Scandinavian mountain range includes glacial landforms from the last deglaciation as well as from earlier glacial stages. One of the most prominent landform groups from earlier glacial stages, and the most diagnostic for ice sheet reconstruction, is a set of lateral moraines. In this paper, we describe these lateral moraines within a key area around Kvikkjokk, northern Sweden. Position of these lateral moraines in relation to the last deglaciation patterns indicates that they were formed before the last glacial maximum (LGM). The location and morphology of moraines show that they were deposited by a mountain centred ice sheet with outlet glaciers along major valleys, emanating from the highlands west of the Kvikkjokk area. This ice sheet was likely less than 170-km wide and no more than 600-m thick. Climatologically and glaciologically, we expect the relict lateral moraines to have been deposited before 75 ka BP (marine oxygen isotope stage 4). Their preservation is a consequence of subsequent overriding of nonerosive cold-based ice. Ice-marginal landforms and deposits from mountain centred ice sheet configurations in Fennoscandia are scarce. Therefore, the relict lateral moraines are important tools for reconstructing these elusive early glacial stages, possibly correlated to the ice sheet inception.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Goodfellow, Bradley, et al.
(författare)
-
Relict non-glacial surfaces in formerly glaciated landscapes: dynamic landform systems?
- 2007
-
Ingår i: Geophysical Research Abstracts.
-
Konferensbidrag (refereegranskat)abstract
- Relict non-glacial surfaces occur within many formerly glaciated landscapes and containimportant information on past surface processes and long-term landscape evolution(Goodfellow, 2007). While cosmogenic dating has confirmed the antiquity ofrelict non-glacial surfaces, the processes that contribute to their evolution and, consequently,the time scales over which they develop remain poorly understood. Of particularimportance is the possibility that relict non-glacial surfaces may provide geomorphicmarkers for the reconstruction of preglacial landscapes, which would allowsubsequent glacial erosion to be quantified. Furthermore, relict non-glacial surfacesmay also hold information on preglacial and interglacial environmental conditions.An investigation of relict non-glacial surfaces was undertaken through remote sensing,mapping and analysis of surfaces in a GIS, and regolith studies involving cosmogenicdating-, grain size-, X-ray diffraction-, and X-ray fluorescence analyses. Onthe basis of these on-going studies, we show that depending on spatial variables suchas bedrock lithology, slope, regolith thickness, and the abundance of fine matrix andwater some surfaces are denuding very slowly, while others display more rapid denudation.High spatial variability in denudation rates results in changing surface morphologiesover time. Rather than being static preglacial remnants, relict non-glacialsurfaces are dynamic features that have evolved during the Quaternary. While reconstructionsof preglacial landscapes and subsequent quantifications of glacial erosionfrom relict non-glacial surfaces remain valid, the Quaternary evolution of these surfacesshould also be considered.Goodfellow B.W., 2007. Relict non-glacial surfaces in formerly glaciated landscapes.Earth-Science Reviews, 80(1-2): 47-73.
|
|
| 8. |
- Goodfellow, Bradley, et al.
(författare)
-
Relict non-glacial surfaces in formerly glaciated landscapes: dynamic landform systems?
- 2007
-
Ingår i: Quaternary International.
-
Konferensbidrag (refereegranskat)abstract
- Relict non-glacial surfaces occur within many formerly glaciated landscapesand contain important information on past surface processes and long-term landscape evolution. While cosmogenic dating has confirmedthe antiquity of relict non-glacial surfaces, the processes that contribute to their evolution and, consequently, the time scales over which they develop remain poorly understood. Of particular importanceis the possibility that relict non-glacial surfaces may provide geomorphic markers for the reconstruction of preglacial landscapes, which would allow subsequent glacial erosion to be quantified. Furthermore,relict non-glacial surfaces may also hold information on preglacialand interglacial environmental conditions. An investigation of relict non-glacial surfaces was undertaken through remote sensing, mapping and analysis of surfaces in a GIS, and regolith studies involvingcosmogenic dating-, grain size-, X-ray diffraction-, and X-ray fluorescenceanalyses. On the basis of these on-going studies, we show that depending on spatial variables such as bedrock lithology, slope, regolith thickness, and the abundance of fine matrix and water some surfaces are denuding very slowly, while others display more rapid denudation. High spatial variability in denudation rates results in changing surface morphologies over time. Rather than being static preglacialremnants, relict non-glacial surfaces are dynamic features that have evolved during the Quaternary. While reconstructions of preglaciallandscapes and subsequent quantifications of glacial erosion from relict non-glacial surfaces remain valid, the Quaternary evolution of these surfaces should also be considered.
|
|
| 9. |
|
|
| 10. |
- Goodfellow, Bradley, et al.
(författare)
-
Weathering processes and Quaternary origin of an alpine blockfield in Arctic Sweden
- 2009
-
Ingår i: Boreas. - : Wiley Interscience. - 0300-9483 .- 1502-3885. ; 38:2, s. 379-398
-
Tidskriftsartikel (refereegranskat)abstract
- The weathering and origin of an autochthonous blockfield in the northern Swedish mountains were investigatedthrough an examination of fine matrix and clasts from two pits excavated across ridge-top sorted circles; one on asummit, the other in a saddle. At the summit, fine matrix chemical weathering is limited to the production of poorlycrystallized Al- and Fe-oxyhydroxides, whereas some additional vermiculitization and gibbsite crystallization occursin the saddle. In both locations, volumes of clay-sized matrix are low, mass balance calculations indicate onlyminor elemental losses and no chemically etched grains are visible under a scanning electron microscope (SEM). Inaddition, soil horizons are absent and chemical weathering intensity is uniformly low across both excavated sortedcircles. Minor clast chemical weathering consists of Fe oxidation, which dominates in the matrix-rich circle centres,and some rind development, which increases in frequency in the clast-rich rings. The dominance of physicalweathering processes and the presence of only minor chemical weathering, in both fine matrix and clasts, indicatethat the blockfield is not a Neogene weathering remnant. Rather, the blockfield has a Quaternary origin, developingduring interglacials, interstadials and the Holocene, primarily through subsurface weathering processes.
|
|
