An investigation of the debris-rich basal ice from Worthington Glacier, Alaska, U.S.A.

Abstract

AbstractThis paper examines the debris-rich basal ice layer from Worthington Glacier, Alaska, U.S.A., a small valley glacier overlying rigid bedrock. The debris-rich basal ice layer studied shows evidence for large-scale longitudinal compressive deformation (isoclinal folds and nappes), similar in style and magnitude features to that reported from push moraines formed in glacial sediments. The debris-rich ice largely comprised stratified solid ice (layers of alternating debris-rich and debris-poor ice) which we suggest results from the tectonic attenuation of folds produced from the deformation of the frozen debris, glacier ice and bubble-rich ice that comprise the initial basal layer of Worthington Glacier. Beneath the glacier lies a thin bed of saturated diamicton which contains evidence of limited movement. It is suggested that this is the result of the partial melt-out of the debris-rich basal ice layer which then behaved as a local (and seasonal) thin deforming layer.It is suggested that this example, from a valley glacier flowing over rigid bedrock, provides further evidence that the processes of sediment transport, incorporation and deposition in the debris-rich basal ice are similar to and linked with those in the deforming layer.