Terminal moraines in the fjord basins of sub-Antarctic South Georgia

Abstract

Sub-Antarctic South Georgia (54° 17′ S, 36° 30′ W, 3755 km2) is a large heavily glacierized island that is 170 km long, 39 km wide and rises to elevations of 2934 m. The island has extensive evidence of past glacial expansion with moraines preserved on land (Bentley et al. 2007), in the fjords (Hodgson et al. 2014) and in glacial troughs that extend 60–100 km to the edge of the continental shelf where some terminate in trough-mouth fans (Graham et al. 2008). A paucity of chronological control means that, at present, it is not possible to identify which of these sets of features mark the limit of a more extensive ice cap from the Last Glacial Maximum (LGM). The glacial geomorphology of nine of the deep glacial fjords on South Georgia has been studied from ship-based geophysical surveys. Despite the different lengths, widths and orientations of the fjords, a relatively consistent pattern of large-scale (102–103 m) submarine geomorphological features is present (Hodgson et al. 2014). Most of the fjords have shallow (30–150 m) inner basins characterized by a range of seafloor sedimentary features including sediment gravity flows, debris fans and slope failures, all of which are associated with high glacigenic sediment supply. The inner …