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- Johansson, Magnus, et al.
(författare)
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Inherited landforms and glacial impact of different palaeosurfaces in southwest Sweden
- 2001
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Ingår i: Geografiska Annaler, 83 A (1-2). ; 83 A, s. 67-89
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Tidskriftsartikel (refereegranskat)abstract
- Landforms are used as analytical tools to separate inherited features from the glacial impact on Precambrian basement rocks in southwest Sweden. The study covers three different palaeosurfaces, the sub-Cambrian peneplain (relative relief 0-20 m) with the character of a pediplain, an uplifted and dissected part of the sub-Cambrian peneplain (r.r. 5-40 m) and an etchsurface (r.r. 20-135 m), presumably sub-Mesozoic. The surfaces were recently re-exposed, probably due to a Neogene upheaval with some pre-glacial reshaping. Strong structural control and no alignment with glacial erosional directions other than those coinciding with structures, are arguments for etch processes as a most important agent for relief differentiation. This is strengthened by the occurrence of saprolite residues and etchforms in protected positions.The glacial reshaping of the sub-Cambrian flat bedrock surfaces is negligible. The glacial impact becomes more evident in the uplifted and dissected parts of the peneplain and within the hilly sub-Mesozoic surface. The higher the initial relief the more effect of glacial erosion on individual hills, both on the abrading side with formation of roches moutonnées and on the plucking side. Detailed etchforms are preserved in protected positions in spite of erosion by a clearly wet-based ice. The magnitude of the Pleistocene glacial erosion is considerably less than the amplitude of the palaeorelief in the entire area. Landscapes of areal glacial scouring have been described as comprised of irregular depressions with intervening bosses scraped by ice and labelled knock and lochan topography, but we suggest that an etched bedrock surface is a prerequisite for this type of landscape to develop.
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| 4. |
- Olvmo, Mats, 1956, et al.
(författare)
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Saprolite remnants as indicators of pre-glacial landform genesis in southeast Sweden
- 2005
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Ingår i: Geografiska Annaler Series a-Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 87A:3, s. 447-460
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Tidskriftsartikel (refereegranskat)abstract
- Twenty-six sites with remnants of gravelly saprolites (grus) have been located in southeast Sweden. Joint block hills (castle kopjes) and steep rock walls with weathered joints as well as rounded boulders are documented to have an origin in deep weathering and subsequent stripping of saprolites. The saprolite remnants and landforms result from the fragmentation of the re-exposed sub-Cambrian peneplain along fracture systems. Only shallow saprolites occur on the elevated intact parts of the sub-Cambrian peneplain, while saprolites up to 20 m thick are encountered in areas where the sub-Cambrian peneplain is fractured and dissected. Neogene uplift with reactivation of the weathering system is thought to be the main cause of saprolite formation. Deep weathering is thus judged to have been the major agent of landform formation in the study area, while glacial and glaciofluvial erosion has contributed mainly by stripping saprolites, detaching corestones, and plucking joint blocks along weathered joints.
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