Genesis of 'hummocky moraines' by thrusting in glacier ice: Evidence from Svalbard and Britain

Michael J. Hambrey*, David Huddart, Matthew R. Bennett, Neil F. Glasser

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

139 Citations (Scopus)

Abstract

Irregular mounds of glacial debris, commonly referred to as 'hummocky moraine', until recently were linked to ice stagnation during rapid climatic amelioration. However, recent work in Scotland has demonstrated that some hummocky moraine, dating from the Younger Dryas event (c. 10 000 year BP), was the product of deposition at active ice margins. Observations at modern high-arctic glacier margins in Svalbard (76-80°N) indicate that some moraines of this type form under a dynamic geological regime, mainly by thrusting in active polythermal ice undergoing strong longitudinal compression. This situation is particularly common where there is a transition from warm-based ice in the interior of a glacier to cold-based ice at the margins or snout. From their morphological similarity (rectilinear slopes facing up-glacier and irregular downglacier faces), and apparent stacking of slabs of sediment of subglacial derivation, it is concluded that some assemblages of British moraines are also the product of thrusting. This process appears to be most dominant in polythermal glaciers, rather than in temperate glaciers. On this basis, it is tentatively suggested that the Younger Dryas in Britain was characterized by a climatic regime similar to that in Svalbard today (mean annual temperature - 5°C; 400-1000 mm precipitation), and that the associated glaciers may have been of polythermar character.

Original languageEnglish
Pages (from-to)623-632
Number of pages10
JournalJournal of the Geological Society
Volume154
Issue number4
DOIs
Publication statusPublished - Jul 1997

Keywords

  • Great Britain
  • Hummocks
  • Moraine
  • Svalbard
  • Thrust faults
  • Younger Dryas

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