Ice dynamics and sediment movement : last glacial cycle, Clyde Basin, Scotland

• Published in: Journal of Glaciology
• Main Author: Finlayson, Andrew G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2012
• Subjects: Ice Sheet; Journal of Glaciology
• Online Access: http://nora.nerc.ac.uk/id/eprint/18859/; https://nora.nerc.ac.uk/id/eprint/18859/1/Finlayson_2012_final.pdf; http://www.ingentaconnect.com/content/igsoc/jog

The nature and behaviour of sediment beneath glaciers influences how they flow and respond to changing environmental conditions. The difficulty of accessing the bed of current glaciers is a key constraint to studying the processes involved. This paper explores an alternative approach by relating sediments under the beds of former mid-latitude ice sheets to changing ice behaviour during a glacial cycle. The paper focuses on the partly marine-based Pleistocene British-Irish ice sheet in the Clyde basin, Scotland. A three-dimensional computation of subsurface glacial sediment distribution is derived from 1260 borehole logs. Sediment distribution is linked to an empirically based reconstruction of ice-sheet evolution, permitting identification of distinctive phases of sedimentation. Maximum sediment mobilization and till deposition (∼0.04 m a-1) occurred during ice advance into the basin from adjacent uplands. Transport distances were generally short. Subglacial processes were influenced locally by the relative stiffness of pre-existing sediments, the permeability of the sub-till lithology, and topography; the resulting mean till thickness is 7.7 m with a high standard deviation of 7.0 m. In places, focused till deposition sealed pre-existing permeable substrates, promoting lower effective pressures. Sediment remobilization by meltwater was a key process as ice margins retreated through the basin.