The time-dependent physics of ice sublimation through thin layers of till is considered, to determine whether sublimation could be sufficiently slow to permit the preservation of ice for 8 Ma in the Dry Valleys, Antarctica. This could only happen if the ice had been very thick, but other evidence (crystal size, dating of other ice-cored moraines) is not consistent with this possibility. Steady-state models suggest that sublimation is rate-controlled by vapor transport. A time-dependent model coupling vapor concentration, air pressure, temperature and ice concentration is formulated, and the resulting equations solved non-linearly. No transient coupling between vapor concentration, air temperature and pressure that substantially slows down sublimation was found in the numerical experiments. This means either that vapor transport is being slowed down by some unconsidered physical process or that the ice is much younger than 8 Ma.

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A number of 45 presumed pingo remnants have been analysed on lithological criteria while measured parameters of pingo remnants can be compared on a spatial scale. Methods used were hand augering and radiocarbon dating. Out of 45 cored sites thirty sites proved to represent pingo remnants after having tested the results according to the set of descriptive criteria. Does a difference in filling types in a spatial analysis influence the choice of early settlers in this region? Results show that two groups of pingo remnants can be distinguished by the nature of the pingo filling. Type 1 pingo remnants with predominantly peat filling are found in the lower valleys between the higher glacial till ridges. Type 2 pingo remnants with equal loam and peat filling are predominantly found on the higher glacial till ridges. Type 2 pingo remnants generally have a greater depth, are more ellipsoid in shape, and have a steeper slope angle than type 1 pingo remnants on the lower terrain. Results indicate that the substrate character influenced the development of infilling of pingo remnants. Marshy environments may have existed for a prolonged period throughout the Holocene in pingo remnants on the glacial ridges, while pingo remnants on the lower terrain are filled in by peat bogs. Landscape evolution based on the results of a distinct dataset of pingo remnants can help to solve archaeological problems of settlement issues when combined with new palaeobotanic data and high resolution dates.

The southern Prince Albert Mountains, between David and Mawson Glaciers (75°30' to 76°S) in Victoria Land, Antarctica, comprise a series of nunataks with elevations ranging from 800m near the coast to 2300 m ~130 km inland. Geochemical and grain-size analyses of tills from these nunataks reveal three major groups of deposits: (1) coarse to medium sandy tills, found on Glaciolly streamlined summit plateaus of Kirk-pat rick Basalt above 2000 ma.s.l.., with geochemical compositions very similar to those of the underlying jurassic Kirkpatrick Basalt; (2) bimodal silty and sanely tills of the Sirius Group with Ferrar/Beacon-dominated geochemical compositions, at elevations of 1300-1600 m a.s.l. on striated summit plateaus and high-elevation terraces; (3) fine-grained tills with high SiO2 contents from ice-cored moraines at the lee sides of large nunataks. The geochemical composition of sandy tills from the highest summit plateaus suggests that valleys had not yet cut through the Kirkpatrick Basalt and into Beacon and Ferrar rocks at the time of deposition. These tills represent a phase of temperate glaciation prior to deposition of diatom-bearing Sirius Group tills. The latter were deposited after a first phase of landscape dissection as inferred from geochemical data. The fine-grained ice-cored moraines are late-Pleistocene basal tills. The presence of pre-Pliocene Glacial deposits on high mountain summits in the Prince Albert Mountains has implications for the interpretation of high-elevation Sirius Group sediments in other areas of the Transantarctic Mountains. It is possible that the “Sirius debate” has its origin in interpretations of both thin, barren pre-Pliocene deposits on high mountain summits and thick sequences of diatom-bearing deposits in valleys elsewhere in the Transantarctic Mountains. Both types of deposits are associated with the Sirius Group, but they belong to separate Glacial episodes.

ABSTRACT. Glacio-geological field work and radar ice-thickness sounding were carried out in the area between David and~1awson Glaciers. A subglacial topographic map has been compiled from radio-echo-sounding data. The northern part of this map shows that the trench of David Glacier reaches a depth of more than 1000 m below sea level. The area south of David Glacier comprises a landscape of nunatak elusters dissected by glaciated valleys with iee thicknesses as much as 800 m. Subglacial cirques occur at the outer margins of the nunatak clusters. A model for the regional glacial history is proposed. It starts with a major deglaciation in the Pliocene, which results in marine transgression in basins west of the Transantarctic .Mountains. During the late Pliocene, the ice advanced towards the northeast, depositing a thin layer of (Sirius Group) till containing reworked mid-Pliocene marine diatoms. Due to accclerated mountain uplift, the ice cut iIlto the pre-Pliocene peneplain, eroding broad valleys. A period of ice-sheet retreat followed to expose a landscape of large nunataks separated by wide valleys. During this period, local cirque glaciation occurred. \Vhen the ice sheet advanced again, another phase of uplift forced the glaciers to cut deeper into the valleys. Probably since the Last Glacial~1aximum the ice surface has lowered by about 100 m.