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Evidence for cold-based ice at low altitudes: Preservation of a preglacial fluvial valley system in the Dyfi basin, Wales (poster)
University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för samhällsbyggnad. (Geomatik/Geomatics)
Institute of Geography and Earth Sciences, Aberystwyth University, Wales. (Centre for Glaciology)
Institutionen för naturgeografi och kvartärgeologi, Stockholms Universitet. (Paleoglaciology)
Institute of Geography and Earth Sciences, Aberystwyth University, Wales. (Centre for Glaciology)
2009 (English)Conference paper, Published paper (Other academic)
Abstract [en]

Coastal valleys in the west part of mid-Wales, such as the Mawddach, Dysynni, Tal-y-llyn and Dyfi, are believed to have acted as corridors for ice which drained the Welsh Ice Cap during the Devensian. Analysis of detailed digital elevation models and interpretation of satellite images and aerial photographs show the existence of large variations in the amount of glacial modification between these valleys. Although all the valleys are glacially over-deepened along Silurian fault lines, only the Dyfi basin exhibits a dendritic pattern, with V-shaped cross profiles and valley spurs typical of valleys formed by fluvial processes. Connectivity analysis of the Dyfi basin shows that it exhibits a nearly dendritic pattern with connectivity α and β values of 0.74 and 1.01 respectively, with little glacial modification of the preglacial fluvial valley pattern in the form of valley breaching. It is proposed that the general river valley morphology of the Dyfi basin is of a pre-Late Devensian age. Several examples have been identified of glacial meltwater incision into a well-developed pre-existing river valley system, causing river capture across watersheds. The degree of preservation of the pre-glacial fluvial valley system within the Dyfi basin indicates limited modification by glacial processes, despite the area being subjected to Late Devensian glacier activity. It is possible that major parts of the basin were covered by cold-based or slow-moving ice close to or under a migrating ice divide, with the major ice drainage occurring along the weaker zone of the Pennal Fault, causing minor adjustments to the surrounding interfluves and uplands.

Place, publisher, year, edition, pages
2009.
Keyword [en]
Palaeoglaciological reconstruction, glacial erosion, preglacial drainage pattern, Wales.
National Category
Physical Geography Climate Research Geosciences, Multidisciplinary Remote Sensing
Identifiers
URN: urn:nbn:se:hig:diva-10522OAI: oai:DiVA.org:hig-10522DiVA: diva2:444549
Conference
The International Glaciological Society British Branch 34th Annual Meeting, University of Sheffield, 2-3 September, 2009
Available from: 2011-09-29 Created: 2011-09-28 Last updated: 2011-11-24Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
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  • ieee
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Language
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Output format
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