The formation and development of proglacial overdeepenings at a contemporary Piedmont lobe glacier :Skeiðarárjökull, South East Iceland

Abstract

The genesis of overdeepenings in proglacial environments has been investigated within both the Quaternary and pre-Quaternary glacial-geologic record. These landforms are important as they can control the behaviour of glaciers and ice sheets through their impact upon subglacial meltwater routing and the glacial hydrological regime. The formation of such landforms has not been studied in detail at contemporary glacier margins, constituting a major gap in our understanding. This research aims to identify the processes that are responsible for the formation of overdeepenings at the margin of Skeiðarárjökull, south east Iceland, which is comparable to the outlet glaciers of the Quaternary and older glacial-geologic record. Through detailed sedimentological and geomorphological analysis, this thesis tests existing models for the formation of overdeepenings, and identifies a number of new processes which had not previously been attributed to the formation of these landforms within contemporary glacial environments. In addition to the erosive role of meltwater, this work has identified that sandur aggradation, ice stagnation, ice fracturing, variations in meltwater routing, and the formation of subglacial bedforms such as eskers can all play a key role in the formation of overdeepenings at contemporary glacier margins. The evidence presented within this thesis, which demonstrates that overdeepenings are not exclusively formed as a result of erosion, and that preferential deposition of sediments can lead to their genesis, is a huge leap from our current understanding. It has found that overdeepenings can form as a result of processes associated with the interactions of individual landforms within the wider proglacial landsystem, and that the development of the system as a whole is more important than individual processes.