A model of the glacial retreat of upper Rennick Glacier, Victoria Land, Antarctica

Abstract

The morphology of the Lichen Hills in the upper section of Rennick Glacier,Victoria Land, Antarctica, is summarised as follows: (a) a top surface on the volcanic rocks with scattered erratic blocks; (b) an exhumed Kukri Peneplain, sculptured with roches moutonne¨es with striae and crescentic gouges on which lie moraines and patches of drift of mainly volcanic rocks; (c) a granitic bedrock eroded by glaciers into sharp peaks and cirques, on top of which there is a glacial drift attributable to ancient blue-ice areas higher than those observed at present and which may be correlated with the Terra Nova drift (Late Wisconsin); (d) various Holocene ice-cored moraines that are pushed to the lee side of the nunataks and are often banded in strips of different lithology. The bands of the Holocene moraines are related to the rock complexes that became exposed from the ice during the lowering of the surface of the glacier. Analysis of the lithology and pattern of the supraglacial debris, as well as of the blue-ice areas, allows us to construct a depositional model for the moraines, and to relate the glacial drift to blue-ice areas existing since the Last Glacial Maximum (LGM). The proposed model shows the different stages of recession of upper Rennick Glacier that are also valid for similar situations observed in northernVictoria Land. A surface lowering of upper Rennick Glacier of several hundred metres shows that significant changes have occurred at the Pacific edge of the East Antarctic ice sheet since the LGM.

TALDICE-1 age scale of the Talos Dome deep ice core, East Antarctica

“…Elevation changes during the Last Glacial Maximum (LGM) have been triggered by the progression of the grounding line up to the continental margin in response to the glacial sea level lowering (Anderson et al, 2002). The maximum elevation change is consistent with analyses of moraine deposits in the upper part of Rennick Glacier (Meneghel et al, 1999 The increased dome elevation during part of the deglaciation resulted from the increase of accumulation rate. We suggest that the dome started to lower its elevation when the grounding line retreated from its LGM position between 14.3 and 12 kyr BP (Anderson et al, 2002).…”

Geophysical survey at Talos Dome, East Antarctica: the search for a new deep-drilling site

“…On the other hand, the ice cover in the central part of East Antarctica was generally thinner (by about 150–200 m) than today, and its thickness varied mainly according to accumulation fluctuations (Ritz and others, 2001; Huybrechts, 2002). The surface elevation of the Talos Dome drainage area during the LGM, present in the lower section of the glacier, rose to 1100 m (close to the LGM grounding line), whereas that of the upper segment remained virtually unchanged (Priestley and Reeves Glaciers) or showed a modest thickening (100–200 m) in upper Rennick Glacier (Orombelli and others, 1991; Meneghel and others, 1999). The extensive presence of meteorites in the Frontier Mountain blue-ice-field area and their terrestrial ages, attributed to the presence of blue-ice meteorite traps during full glacial times (Delisle and others, 1989; Folco and others, 2002), suggest that a moderate change in elevation occurred.…”

Antarctic geomorphological and glaciological 1 : 250 000 map series: Mount Murchison quadrangle, northern Victoria Land. Explanatory notes

“…The lobe west of Lemaster Bluff also deposited a small Holocene ice-cored moraine on the bedrock. Meneghel and others (1999) described a particular kind of banded floating moraine at Lichen Hills. Bands of different lithology (light-coloured granite and dark-coloured volcanic rocks) possibly formed in relation to the progressive lowering of the ice surface due to glacier retreat after the Last Glacial Maximum (LGM).…”