Australian deserts - Climatic Change in Deserts - page 433

Table 22.1. Cenozoic vegetation and climate in Australia. (Based on data in Alley
and Beecroft, 1993 ; Alley et al., 1996 ; Alley, 1998 ; and Martin, 2006 .)

Palaeocene-early
Eocene

Warm and humid; mostly warm to cool temperate rainforest; centre
seasonal rainfall; north-west dry.

Mid-late Eocene In centre sclerophyll vegetation on slopes and ridges; rainforest

restricted to damp valley floors

Latest Eocene-
earliest Oligocene

Abrupt ocean cooling; decrease in megathermal angiosperm
diversity across the continent
Early-mid-Miocene Warm and humid; forest types highly diverse; woodland and
Casuarinaceae forests more common; centre warm with high
seasonal evaporation; rivers dry out in west; first major onset of
aridity
Late Miocene Cool and dry; rainforests shrink; increase in Eucalyptus/
Casuarinaceae sclerophyll forests in central south-east; regular
burning of eucalypt forests; rainforests persist along east coast and
in highlands; centre more arid with dry woodland and chenopod
shrubland
Pliocene Grasslands develop in central north; rainforests shrink further
Early Pleistocene Modern climatic regime but wetter; glacial-interglacial cycles with
open shrubland/grasslands/herbfields during arid glacials
alternating with wooded vegetation during warm wet interglacials
Mid-Pleistocene Change to drier climate at 0.5 Ma; still wetter than today.

Last interglacial Warm and wet; the last major wet interval

LGM Cold and dry

Holocene Brief warm, wet intervals

original drainage network that originated between Early Cretaceous and Late Eocene
times (130-40 Ma) became progressively disrupted, so that by middle Miocene times,
these rivers had ceased to flow and are evident today as a linear series of salt pans
(Bunting et al., 1974 ; Van de Graaff et al., 1977 ; Salama, 1997 ; Zheng et al., 1998 ;
Zheng et al., 2002 ). But the most overwhelming outcome was the movement of much
of Australia during the last 30 million years into tropical latitudes dominated by
anticyclonic conditions and dry, subsiding air. By about 100 Ma, more than 60 per
cent of northern and western Australia was located between 60 ° S and 40 ° S. By 80Ma,

only the southern margins of the continent lay south of 60 ° S, and by about 50 Ma,

virtually all of Australia was located between latitudes 60 ° S and 30 ° S.

22.5 Cenozoic vegetation history and progressive desiccation
The preservation of fossil spores and pollen in sediments ranging back to the early
Cenozoic has made it possible to reconstruct a reasonably comprehensive history of
changes in the Cenozoic vegetation of both Antarctica (Truswell and Macphail, 2009 )
and Australia (Alley and Beecroft, 1993 ; Alley and Lindsay, 1995 ; Markgraf et al.,
1995 ; Alley et al., 1996 ; Alley, 1998 ; Alley et al., 1999 ; Martin, 2006 ). Table 22.1