Apron Entrainment at the Margins of Sub-Polar Glaciers, North-West Ellesmere Island, Canadian High Arctic

• Published in: Journal of Glaciology
• Main Author: Evans, David J.A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1989
• Subjects: Ellesmere Island; Journal of Glaciology
• Online Access: http://dx.doi.org/10.1017/s0022143000009230; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000009230

Abstract From observations on the sub-polar glaciers of Phillips Inlet, north-west Ellesmere Island, neither complex basal thermal regimes nor internal thrusting need be invoked to explain all types of debris distribution in the basal ice of sub-polar glaciers. Debris is present in the terminal ice cliffs as: (1) debris-poor folia expressing internal flow patterns; (2) debris-rich bands of various thickness; and (3) augens or clots. Debris-rich bands and augens are concentrated predominantly in the basal ice, contain a wide range of grain-sizes, cut across debris-poor folia, rarely extend >1 m laterally, and are irregularly spaced. Observations on patterns of entrainment and contemporary processes at ice margins, together with clast-shape analyses, suggest that the recycling and re-incorporation of fluvial/deltaic sediment, aprons, and pro-glacially thrusted blocks at the ice face are an alternative process of debris entrainment to basal plucking and large-scale freeze-on at the base of the glacier. The most active processes observed at the glacier margins are fluvial, and the origins of some debris-rich bands and augens are linked to thermal-erosional niches and abandoned meanders in the base of the glacier cliff face. Because the large-scale accumulation of ice-cored debris at glacier snouts represents periods of increased run-off and snout recession (specifically during the early Holocene), basal and englacial debris concentrations resulting from glacial over-riding and re-incorporation have great palaeoclimatic significance.