Australian deserts - Climatic Change in Deserts - page 432

Figure 22.8. Cenozoic environments of southern Australia. (From Williams, 2009a ,
after McGowran et al., 2004 , fig. 9.)
Antarctica saw the creation of mountain glaciers, followed by the growth of a major
ice cap, first in East Antarctica 33-34 Ma ago and later in West Antarctica.
As the Australian plate moved northwards, there was intermittent volcanic activity
and spasmodic uplift of the Eastern Highlands. Initial uplift of these highlands may
have already begun during the late Cretaceous. Uplift showed considerable lateral
variation (van der Beek et al., 2001 ). In the upper Macquarie Basin, in eastern New
South Wales, uplift reached a peak during the Middle-Late Miocene, with river
incision after that due to climatic and not tectonic causes (Tomkins and Hesse, 2004 ).
Wellman and McDougall ( 1974a ; 1974b ) obtained several hundred potassium-argon
ages for central volcanoes and valley-fill lavas along the Eastern Highlands, and they
found a linear relation between age and latitude, with lavas becoming progressively
younger to the south. These ages indicate a northward movement of the Australian
plate across one or more stationary hot spots at a mean rate of about 6-7 cm/year,
comparable to the rate deduced from sea floor spreading and paleomagnetic data.
Several important conclusions may be drawn from this brief sketch of Mesozoic
and Cenozoic tectonic events. The topographically controlled pattern of precipitation
in eastern Australia is unlikely to have changed very much during the past 30 million
years or so. Likewise, the initiation of the mainly westward flowing drainage in
eastern Australia extends well back into the Cenozoic. In western Australia, the