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Cenozoic landscape evolution in northern Sweden: Geomorphological interpretation within a GIS-framework
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The large-scale bedrock landscape in northern Sweden has a complex evolution history of planation, uplift, transgression, burial, weathering, and erosion. The aim of this thesis is to examine the long-term development of the area.

Terms for base-level surfaces in the area are defined. A combination of GIS-analyses of digital elevation models and field work is used to explore landform characteristics and formation. Inselbergs east of the northern Scandes in northern Sweden are used as a basis for describing landscape development.

In total, 794 inselbergs are identified in the study area. The inselbergs are classified according to their degree of glacial erosion. The Parkajoki area, with low glacially modified inselbergs, tors, boulder fields and saprolites, has been shown to have largely escaped Quaternary glacial erosion and is taken as a type area to describe the late-Neogene landscape development prior to glaciation. The removal of Neogene saprolite mantles at the inselberg feet in areas of glacial erosion increased inselberg relief during the Quaternary by 10-20 m. For landscape evolution further back in time, beyond the Neogene, the hypsography of the study areas shows at least two palaeosurface generations in the northern Scandes and at least four palaeosurface generations on the inselberg plains. The distribution of inselbergs in relation to palaeosurface generations in the same elevation intervals suggests land uplift with a tilt towards the SE-ESE. Eocene marine diatom findings at 260 m a.s.l. in Finland, 200 km east of the study area, indicate a pre-Eocene age of the inselberg plains above this elevation.

The development of today’s inselberg plains likely started in the late Mesozoic, with a sub-Mesozic etch surface that was subjected to land uplift at the late Mesozoic-Paleocene transition during breakup of the Atlantic. The great antiquity of the northern Swedish bedrock landscape stands as an analogy for shield areas in for example Australia and Africa.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography and Quaternary Geology, Stockholm University , 2009. , 23 p.
Series
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 19
Keyword [en]
Long-term geomorphology, northern Sweden, base-level surface, inselbergs, digital elevation models, field observations
National Category
Physical Geography
Research subject
Physical Geography
Identifiers
URN: urn:nbn:se:su:diva-30711ISBN: 978-91-7155-966-1 (print)OAI: oai:DiVA.org:su-30711DiVA: diva2:274296
Public defence
2009-12-04, De Geersalen, Geovetenskapens Hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defence, the following papers were unpublished and had a status as follows: Paper 2: In press. Paper 3: Manuscript. Paper 4. Manuscript. Available from: 2009-11-12 Created: 2009-10-23 Last updated: 2010-04-22Bibliographically approved
List of papers
1. Terminology of long-term geomorphology: a Scandinavian perspective
Open this publication in new window or tab >>Terminology of long-term geomorphology: a Scandinavian perspective
2009 (English)In: Progress in physical geography, ISSN 0309-1333, E-ISSN 1477-0296, Vol. 33, no 2, 163-182 p.Article in journal (Refereed) Published
Abstract [en]

In this paper the terminology used in long-term geomorphology is evaluated. Long-term geomorphology is the study of landforms that are of mostly pre-Quaternary, Cenozoic, Mesozoic or even Palaeozoic age. Many terms have been introduced to name the long-term large-scale landforms that persist to the present. The definitions of many of these terms are ambiguous, have changed over time, and their use and meaning is consequently often unclear. An attempt is made to clarify definitions, when possible, and to facilitate more concise usage of these terms. Long-term geomorphology deals in great parts with the lowering of a land surface to the base level (mostly sea level), leaving a new land surface. The largest group of terms concerns descriptions and genetic models for these kinds of new land surfaces collectively called “base level surfaces” here. Other terms discussed here relate to relict and preglacial landforms and regional terms for stepped surfaces. Terminology is discussed with particular reference to examples from and its use in Scandinavia. There is a long history of long-term geomorphology study in this region. Scandinavia is unique in the respect that pre-Quaternary landforms where repeatedly covered by Quaternary ice-sheets but often survived with different degrees of glacial modification. The usage of the terms in question is discussed from the view of long-term geomorphology in that area.

Place, publisher, year, edition, pages
Sage publications, 2009
Keyword
base level surface, long-term geomorphology, preglacial, relict, Scandinavia, terminology
National Category
Physical Geography
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-30709 (URN)10.1177/0309133309338138 (DOI)000268156600002 ()
Available from: 2009-10-28 Created: 2009-10-23 Last updated: 2017-12-12Bibliographically approved
2. The impact of Quaternary glaciations on inselbergs in northern Sweden
Open this publication in new window or tab >>The impact of Quaternary glaciations on inselbergs in northern Sweden
2010 (English)In: Geomorphology, ISSN 0169-555X, E-ISSN 1872-695X, Vol. 115, no 1-2, 56-66 p.Article in journal (Refereed) Published
Abstract [en]

We investigate the glacial modification of inselbergs (large, isolated bedrock hills) in northern Sweden. Inselbergs are generally regarded as products of deep weathering (etching) and stripping under warm and humid climates. Unlike inselbergs found in the tropics, the inselbergs in northern Sweden were exposed to ice sheet glaciation for long periods of the Quaternary. We used DEMs to examine 794 inselbergs in our study area and they were classified according to their degree of glacial modification. Bedrock structural control was assessed using GIS data on the regional geology. Clusters of inselbergs were mapped in the field for features indicative of glacial erosion, such as glacial cliffs and stripped bedrock surfaces, and for features indicative of limited erosion, such as tors and blockfields. The results of the study indicate that inselbergs in the area were mostly modified by Quaternary ice sheets only to a low or moderate extent and that the degree of glacial erosion is dependent on their relief and location. Inselbergs with a relative relief of < 100 m and in areas of lower absolute relief experienced the strongest glacial modification, where the strongest glacial modification can result in lateral erosion of the inselberg flanks. Inselberg summits often display signs of minimal glacial erosion, such as tor-like bedrock outcrops with signs of strong weathering. In summary, we argue that inselbergs in northern Sweden have largely retained their pre-Quaternary shape despite long periods of ice sheet cover.

Place, publisher, year, edition, pages
Elsevier, 2010
Keyword
Inselbergs, northern Sweden, glacial modification, Pre-Quaternary landscape
National Category
Natural Sciences
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-30710 (URN)10.1016/j.geomorph.2009.09.030 (DOI)000274843800006 ()
Available from: 2009-10-28 Created: 2009-10-23 Last updated: 2017-12-12Bibliographically approved
3. Multi-phase development of a glaciated inselberg landscape
Open this publication in new window or tab >>Multi-phase development of a glaciated inselberg landscape
(English)Manuscript (preprint) (Refereed)
Abstract [en]

We investigate the evolution of a glaciated inselberg landscape in northern Sweden since the late Mesozoic, c. 65 million years ago. The study area is part of the Fennoscandian shield and has been stripped of cover rocks and also largely of weathering mantles by preglacial and glacial erosion to leave low relief inselberg plains, with a thin cover of Quaternary deposits. We use these inselbergs as the basis for study of the impact of glacial and preglacial erosion on the shield landscape. GIS-analyses of digital elevation models (DEMs) enable us to identify the morphometry of the inselbergs. Field mapping and mechanical excavations of inselberg margins allow links to be explored between dome-like granite inselbergs and sheet structures and to examine till and saprolite mantles. Very low glacial erosion in the Parkajoki area allows the final stages of preglacial relief development to be reconstructed for the Late Neogene. The hypsometry of the study area, in combination with inselberg elevation and distribution, allows four palaeosurfaces to be identified.

 

The effects of glacial erosion on the bedrock forms of the inselbergs of the study area were generally restricted to inselberg streamlining by steepening of inselberg flanks. The inselberg landscape relief was enhanced by the removal of saprolite mantles during the Quaternary glaciations. The saprolites formed during the late Neogene, thin or absent close to the inselberg summits and of 10-20 m thickness at the inselberg feet and on the plains. The inselbergs are much older features, however, and deep kaolinization and soft ores are evidence for development by etching from a Mesozoic base level surface. Eocene marine clays on the continuation of the inselberg plains in northern Finland at around 260 m a.s.l. indicate that the inselberg plains above the Pakko palaeosurface generation predate the Paleogene-Eocene thermal maximum. Erosion rates, calculated for two reconstructed summit envelope surfaces, range between 1.5m/Myr and 4.8m/Myr since the late Mesozoic. The inselberg plains of northern Sweden are therefore directly comparable to other shield landscapes in extra-glacial areas that have experienced episodes of deposition of thin cover rocks, long periods of weathering and very low long term rates of erosion.

Keyword
Inselbergs; shield area; DEM-analysis; glacial erosion; weathering and stripping
National Category
Physical Geography
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-30851 (URN)
Available from: 2009-10-28 Created: 2009-10-28 Last updated: 2010-01-14Bibliographically approved
4. DEM-analysis of palaeosurface remnants in the mountain zone of northern Sweden
Open this publication in new window or tab >>DEM-analysis of palaeosurface remnants in the mountain zone of northern Sweden
(English)Manuscript (preprint) (Refereed)
Abstract [en]

Palaeosurface remnants are parts of old planation surfaces that have been elevated and partly down-cut by subsequent erosion. Such surfaces constitute an important landscape element when reconstructing the evolution of a landscape’s tong term development, although their morphological identification may be uncertain. In this study we examine to which degree palaeosurface remnants and surface generations can be identified objectively by GIS-analyses. A combination of fieldwork and GIS-analysis of digital elevation models (DEMs) was used to investigate palaeosurface remnants in two study areas, Ätnajåkki valley and Tjeuralako plateau in the northern Scandes of Sweden.

Our results indicate that surfaces with an inclination of less than 11 °, and that were not affected by glacial erosion, correspond well with palaeosurface remnants as mapped subjectively in the DEM, air photos and in the field. Peaks in the hypsographic curves, at similar elevation intervals for both areas, show the altitudinal distribution of several palaeosurface generations that were identified in the field.

The DEM analysis is shown to be a useful tool, but subjective mapping of glacially eroded areas is necessary to exclude glacially eroded areas, some of which may otherwise be misinterpreted as palaeosurface remnants, in the DEM. Hence, the combination of field observations and GIS-analyses is important when mapping and analysing palaeosurface remnants and their distribution correctly in a DEM. The method shown is nonetheless straightforward and reproducible.

Keyword
Palaeosurface remnants; GIS-analysis; long-term landscape development; northern Scandes
National Category
Physical Geography
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-30852 (URN)
Available from: 2009-10-28 Created: 2009-10-28 Last updated: 2010-01-14Bibliographically approved

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