Evidence for cold based ice: Preservation of a preglacial fluvial valley system in the Dyfi River basin, Mid-Wales
2007 (English)In: BSG abstracts, 2007Conference paper (Other academic)
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 DEMs 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.
It is proposed here 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 moderate 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, with the major ice drainage occurring along the weaker zone of the fault line, causing minor adjustments to the surrounding interfluves and uplands. The findings are important for palaeoglaciological reconstructions of the Welsh Ice Cap.
Place, publisher, year, edition, pages
palaeoglaciological reconstructions, glacial erosion, preglacial drainage pattern, Wales.
IdentifiersURN: urn:nbn:se:su:diva-21110OAI: oai:DiVA.org:su-21110DiVA: diva2:187636