HOLOCENE ISOSTASY AND LATE CENOZOIC DEVELOPMENT OF LANDFORMS INCLUDING BEAVER AND RADOK LAKE BASINS IN THE AMERY OASIS, PRINCE-CHARLES-MOUNTAINS, ANTARCTICA

Geomorphological observations show no detectable uplift (i.e. falling relative sea level) of Amery Oasis since the establishment of relative ly stable sea level during the mid-Holocene. The observations around t he basin of Beaver Lake include an absence of raised shoreline feature s, the presence down to the present tidal limit of in situ ventifacts and residual landforms, the cliffed southern shoreline and adjacent sh allow subhorizontal floor of Beaver Lake, and the composition of recen t moraines on the basin's north eastern edge. This lack of Holocene up lift is consistent with low uplift rates observed from coastal eases o f East Antarctica and suggests minor, rather than major, changes to th e Antarctic ice sheet during the most recent Quaternary glacial cycle. The formation of Beaver basin is attributed to late Cenozoic glacial excavation by south flowing ice of the palaeo-Nemesis Glacier, initial ly eroding when relative sea level was higher than it is today. The ba sin containing Radok Lake was excavated by the palaeo-Battye Glacier p robably when most effective during the numerous long cold periods of t he late Cenozoic. The field evidence from landforms and the presence o f marine fossil deposits suggests Amery Oasis was not overrun by erosi ve ice since at least the Pliocene, major ice streams such as Lambert Glacier flowing then, as now, around the oasis.