Geoscience Reference
In-Depth Information
(
1989
), who before settling in Australia had worked in northern Nigeria monitoring
the dust flux of the Harmattan (McTainsh,
1980
; McTainsh,
1984
; McTainsh,
1987
).
Hesse (
1994
) investigated long-term trends in dust flux preserved in deep-sea sediment
cores from the Tasman Sea and managed to tease out a climatic signal from changes
in dust accumulation rates (see
Chapter 9
).
The fossil river systems of the Riverine Plain in south-east Australia have been
the object of investigation since the time when these fertile alluvial plains were used
for irrigated farming more than a century ago, not least because the buried channels,
or 'deep leads', were often rich in alluvial gold. Schumm (
1968
;
1969
) introduced
the concept of 'river metamorphosis' to his peers in Australia during his pioneering
research into the 'prior channels' and 'ancestral channels' in the lower Murrum-
bidgee basin. Bowler (
1978a
) built on the foundations established by Schumm and
earlier workers in his research on the age and hydrologic significance of the different
generations of paleochannels still clearly visible on the surface of the Riverine Plain,
as discussed in
Chapter 10
.
The lakes of inland Australia have also provided useful insights into past changes in
hydrology and climate (Bowler,
1978b
;Bowler,
1981
). Lake Eyre is at present a vast
salt pan which is dry in most years but receives occasional floods via Coopers Creek
and other rivers flowing through the 'Channel Country' of south-west Queensland
during exceptionally wet years, including 2011 and 2012. Formerly higher lake levels
are evident in the Quaternary lake sediments and associated shorelines preserved in
favoured localities around the lake (Magee et al.,
1995
; Magee,
1998
; Magee and
Miller,
1998
; Magee et al.,
2004
). Other desert lakes also show signs of vastly greater
depth and extent than they exhibit today (Bowler,
1981
;Bowler,
1998
), and insofar
as their former shorelines have been reliably dated, they throw some useful light on
the climates of the past, as discussed in
Chapter 11
.
One lake, which prompted a re-appraisal of whether the Last Glacial Maximum
(LGM: 21
2 ka) was drier or wetter than today, is Lake George near Canberra.
This topic is discussed in detail in Chapters
11
and
12
, so only a few comments are
needed here. Galloway (
1965b
) mapped the lower limits of late Pleistocene glacial
and periglacial deposits (see
Chapter 13
) in the semi-arid Snowy Mountains of south-
east Australia and deduced from the lower limit of periglacial solifluction deposits
that summer temperatures were 8-12
±
C lower than they are today. The formation of
mountain glaciers and small ice caps is controlled by both temperature and precipit-
ation. Low temperatures in winter and seasonal thawing in summer are the primary
controls over periglacial frost shattering and downslope movement of debris by soli-
fluction. Galloway (
1963
;
1965b
) noted that according to the evidence then available,
Lake George had been a very deep lake (approximately 30 m) at that time. Using a
simple water balance model in which monthly evaporation was a direct function of
inferred monthly temperature, he concluded that annual precipitation over the lake
basin was about two-thirds that of today. He came to a somewhat similar conclusion
from his studies in the semi-arid south-west of the United States (Galloway,
1970
;
°
