Holocene isostasy and late Cenozoic development of landforms including Beaver and Radok Lake basins in the Amery Oasis, Prince Charles Mountains, Antarctica

Abstract

Geomorphological observations show no detectable uplift (i.e. falling relative sea level) of Amery Oasis since the establishment of relatively stable sea level during the mid-Holocene. The observations around the basin of Beaver Lake include an absence of raised shoreline features, the presence down to the present tidal limit of in situ ventifacts and residual landforms, the cliffed southern shoreline and adjacent shallow subhorizontal floor of Beaver Lake, and the composition of recent moraines on the basin's north eastern edge. This lack of Holocene uplift is consistent with low uplift rates observed from coastal oases of East Antarctica and suggests minor, rather than major, changes to the 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, initially eroding when relative sea level was higher than it is today. The basin containing Radok Lake was excavated by the palaeo-Battye Glacier probably when most effective during the numerous long cold periods of the late Cenozoic. The field evidence from landforms and the presence of marine fossil deposits suggests Amery Oasis was not overrun by erosive ice since at least the Pliocene, major ice streams such as Lambert Glacier flowing then, as now, around the oasis.

Limnology and Sedimentary Record of Radok Lake, Amery Oasis, East Antarctica

“…Minor variations in the vertical hydrological profiles reveal that Radok Lake was completely mixed in January 2002 and confirm earlier observations (Wand et al 1987;Adamson et al 1997). Low conductivities and ion concentrations are caused by the supply of ion depleted meltwater from Battye Glacier and the surrounding slopes.…”

“…In late January 2002, the lake ice-cover was observed to be melting at the tip of the northeastern branch. The melt seemed to be of minor importance compared to earlier years (Adamson et al 1997), due to thick snow accumulation and consequent increased albedo during early summer 2001/2002. Snow cover was noticably reduced in early February 2002 and lake ice became exposed, particularly in the central areas of the lake.…”

“…At the southwestern corner Battye Glacier enters Radok Lake forming a floating ice tongue. Meltwater supply from the glacier, the melt stream from Glossopteris Gully (Adamson et al 1997) and to a lesser degree from the surrounding slopes feeds the lake during summer (Wand et al 1987). The lake outlet is formed by the deeply incised Pagodroma Gorge that leads into Beaver Lake, an epishelf lake that is hydrologically connected to the ocean underneath Amery Ice Shelf .…”

“…Radok Lake Basin was formed by Late Cenozoic glacial erosion, i.e., repeated excavation by the paleoBattye Glacier (Adamson et al 1997). However, a widespread ice coverage of Amery Oasis seems to have not occurred during the Last Glacial Maximum.…”

“…However, a widespread ice coverage of Amery Oasis seems to have not occurred during the Last Glacial Maximum. This is suggested by the lack of geomorphological evidence for isostatic uplift during the latter half of the Holocene (Adamson et al 1997). The overdeepening of Radok Lake likely occurred along a tectonically weak zone, the Amery Fault, which runs along the long axis of the lake.…”