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Glasby et al., 2007 ; Haberlah et al., 2010a ; Haberlah et al., 2010b ). The most recent
valley fill is around 35 ka near the base and 17-16 ka near the top of the sequence.
The overall chronology is based on some 30 OSL ages and 100 AMS radiocarbon
ages on shell, charcoal and plant debris. The alluvial clays contain unbroken shells of
freshwater snails and ostracods, and were laid down in perennial wetlands (Williams
et al., 2001 ) and, more locally, as slack-water deposits after major floods (Haberlah
et al., 2010a ). The alluvial clays themselves consist at least in part of reworked wind-
blown dust or loess blown in from the west and deposited on slopes of the north-south
aligned ridges of quartzite, limestone and shale that form the Flinders Ranges. The
fact that this wetland persisted throughout the coldest, driest climatic interval in late
Pleistocene Australia indicates a complex and counter-intuitive response to climatic
change. Williams and Adamson ( 2008 ) have put forward a simple bio-geophysical
model to explain the enigma of a late Pleistocene wetland in the arid Flinders Ranges
during a time of peak regional aridity.
In the semi-arid Snowy Mountains of south-east Australia, the three most recent
glacial advances have been dated using the cosmogenic nuclide 10 Be to 32
±
2.5,
19.1
1.4 ka, with periglacial activity concentrated between 23 and
16 ka (Barrows et al., 2001 ). The orographic snow-line was about 600-700 m lower,
and the lower limit of periglacial solifluction was at least 975 m lower (Galloway,
1965b ). Because this latter limit is roughly equivalent to the 10
±
1.6 and 16.8
±
C isotherm for the
warmest month, the temperature in the warmest month was at least 9
°
°
C cooler than
today (Galloway, 1965b ).
Low summer temperatures would have reduced water losses from evaporation and
transpiration in the Flinders Ranges and elsewhere. Miller et al. ( 1997 ) estimated
that millennial-scale mean temperatures at low elevations in arid inland Australia
between around 45 and 16 ka were at least 9
C lower than they were after 16 ka.
They based their estimates on the temperature-dependent amino acid racemisation
reaction (see Chapter 6 ) in radiocarbon-dated emu eggshells from the continental
interior to reconstruct subtropical temperatures at low elevations over the last 45 ka.
They inferred a sharp change at around 16 ka, followed by rapid warming. These
temperature data suggest that lower temperatures and reduced evaporation may have
been factors in the persistence of wetland ecosystems in the Flinders Ranges (Williams
et al., 2001 ; Williams et al., 2006a ).
Low glacial concentrations of atmospheric carbon dioxide would have favoured
grasses at the expense of trees. Trees act as natural groundwater pumps, so fewer
trees, especially the River Red Gum, Eucalyptus camaldulensis , would lead to rising
groundwater levels. The increase in dust flux was a function of greater aridity, reduced
plant cover, increased wind velocity and wind gustiness (Maher et al., 2010 ; McGee
et al., 2010 ). The grass cover on the hillsides provided an efficient dust trap for loess
blown in from dunes, dry playa lakes and from the exposed continental shelf during
times of glacially lowered sea level. A loess mantle on the slopes would increase
°
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