Controls on bedrock bedform development beneath the Uummannaq Ice Stream onset zone, West Greenland

Timothy P. Lane*, David H. Roberts, Brice R. Rea, Colm Cofaigh, Andreas Vieli

*Corresponding author for this work

Research output: Contribution to journalArticle

11 Citations (Scopus)
7 Downloads (Pure)

Abstract

This paper investigates the controls on the formation of subglacially eroded bedrock bedforms beneath the topographically confined region upstream of the Uummannaq Ice Stream (UIS). During the last glacial cycle, palaeoglaciological conditions are believed to have been similar for all sites in the study, characterised by thick, fast-flowing ice moving over a rigid bedrock bed. Classic bedrock bedforms indicative of glacially eroded terrain were mapped, including p-forms, roches moutonnées, and whalebacks. Bedform long axes and plucked face orientations display close correlation (parallel and perpendicular) to palaeo-ice flow directions inferred from striae measurements. Across all sites, elongation ratios (length to width) varied by an order of magnitude between 0.8:1 and 8.4:1. Bedform properties (length, height, width, and long axis orientation) from four subsample areas, form morphometrically distinct populations, despite their close proximity and hypothesised similarity in palaeoglaciological conditions.Variations in lithology and geological structures (e.g., joint frequency; joint dip; joint orientation; bedding plane thickness; and bedding plane dip) provide lines of geological weakness, which focus the glacial erosion, in turn controlling bedform geometries. Determining the relationship (s) between bedding plane dip relative to palaeo-ice flow and bedform shape, relative length, amplitude, and wavelength has important ramifications for understanding subglacial bed roughness, cavity formation, and likely erosion style (quarrying and/or abrasion) at the ice-bed interface. This paper demonstrates a direct link between bedrock bedform geometries and geological structure and emphasises the need to understand bedrock bedform characteristics when reconstructing palaeoglaciological conditions.

Original languageEnglish
Pages (from-to)301-313
Number of pages13
JournalGeomorphology
Volume231
Early online date18 Dec 2014
DOIs
Publication statusPublished - 15 Feb 2015

Keywords

  • Abrasion
  • Bedrock bedform
  • Glacial erosion
  • Greenland ice sheet
  • Ice stream
  • Quarrying

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