Summary
Vestfold Hills, East Antarctica exhibits marked contrasts in the weathering surface, glacial sediments and terrain between its eastern and western parts. The boundary between these zones coincides with a regional chemical boundary termed the salt line. The area west of the salt line is saturated with marine-derived halite and thenardite that are particularly aggressive agents of rock weathering. In contrast, the area east of the salt line exhibits significantly fewer deposits of these salts. Rock surfaces west of the salt line are characterised by well-developed weathering forms, while glacial polish and striae are largely absent. In contrast, rock surfaces to the east commonly retain glacial polish and striae. In places, differential weathering has caused thin basaltic dykes and felsic veins to stand above the surrounding gneiss. The rate of lowering of the gneiss and dykes to the west of the salt line has been estimated at 0.024 mm and 0.015 mm per year respectively (Spate et al. 1995). These measurements suggest that the weathering surface in parts of Vestfold Hills may record more than 70 ka of subaerial exposure. Glacial sediments are much more abundant, coarser and better sorted northwest of the salt line than to the southeast. The abundant grus produced by physical weathering is coarser grained and better sorted than that produced by subglacial erosion. Such sediment lying on the land surface would be transported and redeposited during glacial advances. The change in nature of the sediments to either side of the salt line, together with the weathering forms found on clasts in the moraines, indicates that the weathering surface prior to the last glacial advance was similar to that of today and must also have developed during long periods of subaerial exposure. The terrain to the west of the salt line has modal hilltop heights of 41-60 m and that to the east 101-120 m. The minimum period of subaerial exposure inferred to create this 60 m contrast in