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in North Atlantic oceanic circulation and low-latitude monsoon activity, although the
precise causal links remain a subject of further investigation.
14.3.2 Speleothem studies from the Negev Desert and adjoining region
The Negev Desert of Israel forms a link between the Sahara Desert to the west and the
Arabian Desert to the east. The Sahara-Arabian desert belt is one of the driest regions
on earth, with less than 50 mm of annual precipitation, although such averages can be
misleading given the very high variations in precipitation from year to year. East of
the Negev is the Dead Sea Rift, with the hyper-saline Dead Sea in the central portion
of the Rift and the Arava Valley lying between the Dead Sea to the north and Aqaba
in the eastern tip of the northern Red Sea to the south.
Tufa deposits in the Arava Valley and speleothems in the Negev Desert were form-
ing sporadically during past interglacials (Waldmann et al.,
2010
). Such depositional
events would have been a result of southerly incursions of moist air, given that north-
ern Israel, including the former freshwater Late Pleistocene Lake Lisan in the Dead
Sea Rift (
Chapter 11
), was low during interglacial times but high during glacial times,
when there was a greater influx of moist air masses from the eastern Mediterranean
during winter (Enzel et al.,
2008
). One consequence of these short-lived moist phases
in the Negev Desert would have been the facilitation of human movement out of Africa
into Eurasia via the Levantine Corridor (Vaks et al.,
2007
; Waldmann et al.,
2010
),
which is discussed in
Chapter 17
. Lazar and Stein (
2011
) found evidence of extensive
recrystallization of coral reefs along the Red Sea shores as a result of widespread
freshwater spring discharge around 140 ka, indicating that humans could have moved
along the Red Sea coast at the start of the last interglacial with ready access to good
water.
A substantial body of work by Matthews, Vaks, Bar-Matthews and their colleagues
has shown considerable geographical variation in speleothem activity across Israel
(Matthews et al.,
2000
;Vaksetal.,
2003
; McGarry et al.,
2004
;Vaksetal.,
2006
;
Vaks et al.,
2007
; Affek et al.,
2008
;Vaksetal.,
2010
). Matthews et al. (
2000
) studied
the D/H ratios in fluid inclusions in two fossil speleothems in Soreq Cave south-west
of Jerusalem and found that cooler, less evaporative conditions were prevalent over
the eastern Mediterranean during glacial times, a finding also confirmed by McGarry
et al. (
2004
). Using 'clumped isotope' thermometry (discussed in
Chapter 7
), Affek
et al. (
2008
) were able to show that temperatures in Soreq Cave were 6-7
°
C cooler
than they are today during the LGM and 3
°
C cooler at 56 ka.
13
C variations in speleothems from a number of caves
scattered across the southern and central Negev Desert was used to reconstruct past
changes in surface vegetation and to determine the probable source of the rainfall
associated with speleothem formation. During the past 350 ka, there were major humid
periods at 350-310, around 310-290, 220-190 and 142-109 ka, of which all except the
18
Oand
Analysis of
