Geoscience Reference
In-Depth Information
Figure 22.5. Flinders Ranges, South Australia. (Photo: Frances Williams.)
22.3 Australian desert landscapes
As with other deserts, it is convenient to group the Australian desert landscapes into
erosional and depositional landforms (Mabbutt,
1977
; Williams,
1984
d; Mabbutt,
1988
). The erosional components include the dissected rocky plateaux of the Yilgarn
and Pilbara regions in the west, the Musgrave, Arunta and MacDonnell ranges in
the centre, and the Flinders Ranges in the south (
Figures 22.5
to 22.7). The rocks
comprising these uplands range in age from Archaean and Proterozoic to Palaeozoic,
and they are in general highly resistant to erosion under the present arid climate. Some
of the rocks in the Yilgarn have an age of 4.2
10
9
years, making them among the
oldest rocks on earth. As a result of this observed resistance to present-day erosional
processes, some workers have concluded that parts of the Australian landscape have
persisted virtually unmodified since the early Mesozoic or even earlier (Twidale and
Campbell,
1991
; Williams,
1991
;Twidale,
1998
;Twidale,
2000
). This hypothesis can
now be tested using measured rates of erosion.
Heimsath et al. (
2010
) measured the cosmogenic
10
Be produced in situ across a
range of rock types and climatic zones in arid Australia. They obtained mean erosion
rates of about 1.5 mMa
−
1
on rocky, weathering-limited slopes in arid central Australia
and rates of 2-11 mMa
−
1
for blocky quartzite slopes in the semi-arid Flinders Ranges
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