Re-interpretation of ‘hummocky moraine’ in the Gaick, Scotland, as erosional remnants: Implications for palaeoglacier dynamics

Research output: Contribution to journalArticle

Abstract

Many glaciated valleys in Scotland contain distinctive, closely spaced ridges and mounds, which have been termed ‘hummocky moraine’. The ridges and mounds are widely interpreted as ice-marginal moraines, constructed during active retreat of mainly temperate glaciers. However, hummocky terrain can form by various processes in glacial environments, and it may relate to a range of contrasting glaciodynamic regimes. Thus, detailed geomorphological and sedimentological studies of hummocky surfaces in Scottish glaciated valleys are important for robust interpretations of former depositional environments and glacier dynamics. In this contribution, we examine irregularly shaped ridges and mounds that occur outside the limits of former Loch Lomond Readvance (≈ Younger Dryas; ~ 12.9–11.7 ka) glaciers in the Gaick, Central Scotland. These ridges and mounds are intimately associated with series of sinuous channels, and their planform shape mimics the form of the adjacent channels. Available exposures through ridges in one valley reveal that those particular ridges contain lacustrine, subglacial, and glaciofluvial sediments. The internal sedimentary architecture is not related to the surface morphology; thus, we interpret the irregularly shaped ridges and mounds as erosional remnants (or interfluves). Based on the forms and spatial arrangement of the associated channels, we suggest that the ridges and mounds were generated by a combination of ice-marginal and proglacial glaciofluvial incision of glaciogenic sediments. The evidence for glaciofluvial incision, rather than ice-marginal moraine formation, at pre-Loch Lomond Readvance glacier margins in the Gaick may reflect differences in glaciodynamic regimes and/or efficient debris delivery from the glacier margins to the glaciofluvial systems.

Details

Authors
  • Benjamin M.P. Chandler
  • Clare M. Boston
  • Sven Lukas
  • Harold Lovell
Organisations
External organisations
  • Queen Mary University
  • University of Portsmouth
  • Stockholm University
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Geology

Keywords

  • Glacier dynamics, Glaciofluvial erosion, Glaciofluvial processes, Hummocky moraine, Meltwater channels, Scotland
Original languageEnglish
Pages (from-to)506-524
JournalProceedings of the Geologists' Association
Volume132
Issue number4
Publication statusPublished - 2021
Publication categoryResearch
Peer-reviewedYes

Bibliographic note

Funding Information: This research was undertaken while BMPC was in receipt of a Queen Mary Natural and Environmental Science Studentship. Fieldwork was also supported by a small grant from the International Association of Sedimentologists , which is gratefully acknowledged. We are grateful to Jon Merritt for support and discussion during this research, BGS Edinburgh for providing access to resources, and Mark Johnson for insightful comments on an earlier version of this manuscript. BMPC would also like to thank Colm Ó Cofaigh and Steph Mills for discussions of this work. We are grateful to the two reviewers, Stephen Livingstone and Richard Waller, for constructive comments that helped us to improve this paper, and to Jonathan Lee for editorial handling. Publisher Copyright: © 2021 Elsevier Ltd Copyright: Copyright 2021 Elsevier B.V., All rights reserved.