Structure and sedimentology of George VI Ice Shelf, Antarctic Peninsula: implications for ice-sheet dynamics and landform development

Abstract

Collapse of Antarctic ice shelves in response to a warming climate is well documented, but its legacy in terms of depositional landforms is little known. This paper uses remote-sensing, structural glaciological and sedimentological data to evaluate the evolution of the c . 25000 km 2 George VI Ice Shelf, SW Antarctic Peninsula. The ice shelf occupies a north–south-trending tectonic rift between Alexander Island and Palmer Land, and is nourished mainly by ice streams from the latter region. The structure of the ice shelf is dominated by inherited foliation and fractures, and with velocity data indicates a largely compressive flow regime. The formation of a moraine complex at the margin of the ice shelf is controlled by debris entrained within foliation and folds. This englacial debris is of basal origin, and includes both local Mesozoic sedimentary and volcanic lithologies, and exotic crystalline rocks from Palmer Land. Folding of basal ice to a high level in the source glaciers on Palmer Land is required to bring the debris to the surface. These results have implications for understanding flow dynamics of ice shelves under compressive flow, and debris entrainment and moraine formation associated with palaeo-ice shelves. Supplementary material: Photographs of ice-shelf morphology, ice facies and ice structure; detailed descriptions of ice facies, including foliation logs, supporting evidence for interpreting sedimentary facies; complete dataset of sedimentological data, including triangular plots of clast shape, clast roundness histograms, particle-size distribution of sand-size and lower, and pie chart of local clasts versus exotic clasts from Palmer Land; and a table summarizing the characteristics of representative clasts in the ice-shelf moraine, based on thin-section analysis, with indication of their provenance are available at http://www.geolsoc.org.uk/SUP18831