Abstract

The Mount Gran area, encompassing Mount Gran and the ice-free Alatna Valley adjoining to the north, is located 77° S. and 161° E. in the rugged, glaciated mountains of southern Victoria Land, Antarctica.

At least two major glaciations are represented in this area. During the first and most extensive glaciation recognized, the A Glaciation, ice came from the inland ice plateau in the west, hollowed out the western end of Alatna Valley, and probably passed through the area to the Ross Sea in the east.

During the second or B Glaciation, ice probably invaded the Mount Gran area from the coastal area in the east. This origin is suggested by the orientation of roche moutonnées and end moraines in Alatna Valley and by the occurrence of erratic boulders of pink granite and pink gneiss on the floor of Alatna Valley and lower elevations of Mount Gran. Such an invasion from the coast may have occurred when sea level was low and there was about 1200 m of ice in the McMurdo Sound-Ross Sea area.

Ablation phenomena immediately adjacent to the glacier fronts suggest recent recession in the Mount Gran area.

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