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310-290 ka humid phase were interglacial events (Vaks et al.,
2010
). The wet phases
were synchronous with times of sapropel accumulation in the Mediterranean (already
discussed in
Chapter 10
), indicating synchronously wetter conditions over the Sahara
and the southern Negev, which facilitated the movement of animals and hominids out
of Africa into Eurasia during brief humid episodes (sandwiched between prolonged
droughts), themost recent of whichwas 140-110 ka ago (Vaks et al.,
2007
). Thesewere
synchronous with similar humid phases recorded in speleothems from northern Oman
and southern Yemen (Fleitmann et al.,
2003a
; Fleitmann and Matter,
2009
; Fleitmann
et al.,
2011
). However, there was never a simple one-to-one correlation between humid
phases in the Negev Desert and interglacials. Vaks et al. (
2006
) identified major humid
intervals in the northern Negev Desert coinciding with glacial phases at 190-150, 76-
25 and 23-13 ka and with interglacial phases at 200-190, 137-123 and 84-77 ka.
The main source of rainfall in the northern Negev was inferred from
18
Ovaluesin
the speleothems to have been from the eastern Mediterranean, with some possible
contribution from tropical southern sources during interglacial episodes. One further
interesting insight to emerge from these studies was the influence of rain-shadow
effects in eastern Israel, with an effective southward migration of the desert boundary
on the eastern flank of the central mountain ridge of Israel during glacial periods and
no change relative to the present during interglacials (Vaks et al.,
2003
).
14.3.3 Speleothem studies from arid and semi-arid Australia
The examples from Israel show that caves that are only a short distance apart can
sometimes show quite different responses to precipitation events, indicating that local
topographic and hydrologic influences always need to be considered. This is also true
of arid southern Australia. For example, a speleothem from Mairs Cave in the arid
northern Flinders Ranges of South Australia, dated between 20 and 15 ka, shows peak
wetness at 17-16 ka (Cohen et al.,
2010b
). Quigley et al. (
2010b
) worked further north
in Yudnamutana Gorge and found an increase in humidity after about 11.5 ka, with
a peak in wetness at 7-6 ka. One possible interpretation of these seemingly disparate
results is that the most northerly of the two sites in the Flinders Ranges reflects the
most southerly advance of tropical summer rainfall at that time, while Mairs Cave
further south reflects the influence of winter rainfall events. Because no attempt was
made to determine the likely precipitation sources, we cannot choose between these
two scenarios.
Other speleothem records from Australia have been used in an attempt to elucidate
the causes of the late Pleistocene megafaunal extinctions in Australia (Prideaux et al.,
2007
; Prideaux et al.,
2009
; Prideaux et al.,
2010
), and are discussed in detail in
Chapter 17
. The 185 to 157 ka stable oxygen and carbon isotope record from Victoria
Fossil Cave at Naracoorte in semi-arid South Australia revealed that during the 178-
162 ka interstadial, regional surface temperatures were anomalously high (possibly
