Bedrock mega-grooves in glaciated terrain: a review

Newton, M.; Evans, D.J.A.; Roberts, D.H.; Stokes, C.R.

Abstract

Bedrock mega-grooves are assemblages of straight and parallel troughs eroded in bedrock, typically over 1000 m in length; most sites occur within the limits of the Last Glacial Maximum, both on- and off-shore. In this paper, we review the current understanding of these important yet enigmatic landforms and propose a framework for their future research. Mega-grooves are important to our understanding of ice sheet dynamics, ice–bedrock interactions and bedrock landscape evolution in glaciated areas. The overall straightness of mega-grooves across the landscape, their parallel alignment to palaeo-ice flow direction, and occurrence below the general land-surface level, has led to their unanimous interpretation as landforms of subglacial erosion. Scenarios proposed for mega-groove formation focus on either glacier ice or subglacial meltwater as the principal agent of erosion, yet none offers a comprehensive explanation. At locations where mega-grooves occur along lines of structural geology, their location, formation and morphology were largely controlled by the bedrock characteristics. Where no underlying structural control is apparent, mega-grooves were likely initiated through glacial abrasion, and subsequently modified through a range of erosional processes, potentially involving multiple morphogenetic agencies and feedbacks operating between bedrock topography and basal ice flow. In the absence of absolute dates, morphostratigraphic analyses suggest mega-groove survival through multiple glacial cycles. No specific ice-flow characteristics have been identified as a condition for bedrock grooving, but it has been suggested that some bedrock mega-grooves are related to ice streaming, which deserves further study. An initial analysis of bedrock grooves with seemingly similar morphology at a range of scales hints at a bedrock – groove landform size continuum, which could be a useful framework for exploring process landform relationships. Future research could usefully focus on quantitative analysis of mega-groove morphology, augmented with detailed field analysis of landform relationships to bedrock structure and lithology, and thereby potentially provide further insight into the age and glaciological significance of these landforms.

Citation

Newton, M., Evans, D., Roberts, D., & Stokes, C. (2018). Bedrock mega-grooves in glaciated terrain: a review. Earth-Science Reviews, 185, 57-79. https://doi.org/10.1016/j.earscirev.2018.03.007

• Journal Article Type: Article
• Acceptance Date: Mar 14, 2018
• Online Publication Date: Mar 24, 2018
• Publication Date: Oct 1, 2018
• Deposit Date: Mar 22, 2018
• Publicly Available Date: Mar 24, 2019
• Journal: Earth-Science Reviews
• Print ISSN: 0012-8252
• Electronic ISSN: 1872-6828
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 185
• Pages: 57-79
• DOI: https://doi.org/10.1016/j.earscirev.2018.03.007
• Public URL: https://durham-repository.worktribe.com/output/1336684