Multiple cosmogenic nuclides document complex Pleistocene exposure history of glacial drifts in Terra Nova Bay (northern Victoria Land, Antarctica)

Abstract

Geomorphological and glacial geological surveys and multiple cosmogenic nuclide analyses ((10)Be, (26)Al, and (21)Ne) allowed Lis to reconstruct the chronology of variations prior to the last glacial maximum of the East Antarctic Ice Sheet (EAIS) and valley glaciers in the Terra Nova Bay region. Glacially scoured coastal piedmonts with round-topped mountains occur below the highest local erosional trimline. They represent relict landscape features eroded by extensive ice overriding the whole coastal area before at least 6 Ma (predating the build-Lip of the Mt. Melbourne volcanic field). Since then, summit surfaces were continuously exposed and well preserved under polar condition with negligible erosion rates on the order of 17 cm/Ma. Complex older drifts rest on deglaciated areas above the younger late-Pleistocene glacial drift and below the previously overridden summits. The combination of stable and radionuclide isotopes documents complex exposure histories with Substantial periods of burial combined with minimal erosion. The areas below rounded summits were repeatedly exposed and buried by ice from local and outlet glaciers. The exposure ages of the older drift(s) indicate multiple Pleistocene glacial cycles, which did not significantly modify the pre-existing landscape. (C) 2008 University of Washington. All rights reserved

A tuff cone erupted under frozen-bed ice (northern Victoria Land, Antarctica): linking glaciovolcanic and cosmogenic nuclide data for ice sheet reconstructions

“…This scenario is similar to the thermal state envisaged for late Miocene and Pliocene ice in northern Victoria Land (Smellie et al 2014), and by modelling studies of the modern Antarctic ice sheet in East Antarctica (Pollard and De Conto 2009;Pattyn 2010). Erratics showing similar edge abrasion and surface oxidation/weathering are common in the region and are known as Terra Nova Drift (Baroni and Orombelli 1987;Orombelli et al 1990;Di Nicola et al 2009). Similarly abraded erratics exposed at c. 16 ka are also present at Cape Adare at 350 m a.s.l., c. 400 km to the north .…”

“…The distribution of the abraded erratics described in this paper and by other authors (e.g. Baroni and Orombelli 1987;Orombelli et al 1990;Di Nicola et al 2009) may suggest that polythermal ice had a widespread distribution in the Mt. Melbourne hinterland during the last glacial, and potentially extended along 400 km of coastal Victoria Land (Harrow Peaks-Cape Adare), at least.…”

“…Studies of environmental change have suggested that the entire region remained in a cold ice thermal regime during the Quaternary, which should have acted predominantly to protect it (Baroni and Orombelli 1987;Orombelli et al 1990;Baroni et al 2005;Di Nicola et al 2009). However, the Harrow Peaks outcrop is draped by numerous erratics of basement granitoid lithologies that are significantly abraded (Figs.…”

Cosmogenic radionuclide dating indicates ice-sheet configuration during MIS 2 on Nordaustlandet, Svalbard

“…To determine whether a sample has a simple or a complex exposure history, the measurement of more than one nuclide is necessary (Anderson et al 1996;Briner et al 2006;Di Nicola et al 2009). The radioactive decay of 10 Be and 26 Al with time will result in a decrease in concentrations of these radionuclides in quartz.…”

“…By plotting such ratio changes in two-nuclide diagrams, one can determine whether a sample experienced a simple or a complex exposure history (i.e. periods of exposure broken by periods of total or partial isolation from cosmic rays) or was exposed to distinct thermal regimes at the bed of former glaciers Miller et al 2006;Di Nicola et al 2009). In these studies it has been shown that a cold-based glacier regime does not erode the bedrock surface sufficiently to eliminate radionuclide isotopes from the former ice-free period.…”