The sedimentological characteristics of basal ice and their preservation within the proglacial environment

Abstract

The identification of distinctive sedimentological characteristics within the basal ice layer (BIL), and their potential preservation within the proglacial environment, is crucial to enhancing our understanding of glaciological conditions beneath ice masses. Though much work has focussed on understanding the nature and formation of basal ice, its diagnostic sedimentological characteristics and the circumstances in which they might be preserved remain unclear.

Field work at Svínafellsjökull in southeast Iceland was carried out to establish whether specific sedimentological characteristics from the BIL could be identified within the proglacial environment. This involved sampling the basal ice and proglacial sedimentology at seven key sites for grain size analysis. Particle size data collected from the BILs of six glaciers from around the world were also used to provide a broader global context.

Six key basal ice types were identified at Svínafellsjökull along with two distinct proglacial landforms (moraines and minor outwash fans) and other proglacial sediments. The findings suggest that basal ice is most easily recognised within the proglacial environment through the transfer of the high volume of silt contained within some basal ice facies (15%), a high silt content (between 50% and 80%) and a low to medium clay content between 15% and 30%.

The results indicate that whilst basal ice sediments are sedimentologically distinct, these distinctive characteristics are not always clearly distinguishable within the proglacial sediments. Future research should therefore utilise a broader range of sedimentological criteria derived from a greater number of sites in order to identify diagnostic criteria more frequently preserved within the proglacial environment.