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errors, tally reasonably well with the intervals of high Blue and White Nile floods
identified here. At the site of Erkowit in the Red Sea Hills (Mawson and Williams,
1984
), there is evidence of permanent stream flow around 1.8-1.6 ka, coinciding with
high White Nile flows but not as yet evident in the much more incomplete Blue Nile
sedimentary record.
10.9 East Mediterranean marine sediment core records
of Quaternary Nile flow
During phases of very high Nile flow, clastic muds rich in continental organic mat-
ter and highly organic sapropels accumulated on the floor of the eastern Mediter-
ranean (Rossignol-Strick et al.,
1982
; Rossignol-Strick,
1985
; Lourens et al.,
1996
;
Rossignol-Strick,
1999
; Mercone et al.,
2001
;Krometal.,
2002
; Larrasoana et al.,
2003
; Ducassou et al.,
2008
; Ducassou et al.,
2009
;Revel,
2010
). Flood deposits
exposed in trenches dug east of the present White Nile near Esh Shawal village
300 km south of Khartoum (Williams et al.,
2003
) show episodes of middle to late
Pleistocene high flow which, within the limits of the dating errors, coincide with sap-
ropel units S8 (217 ka), S7 (195 ka) and S6 (172 ka) (Lourens et al.,
1996
). Sapropel
5 (124 ka) was synchronous with major flooding in the White Nile Valley and with a
prolonged wet phase at around 125 ka at Kharga Oasis in the Western Desert of Egypt
(Kieniewicz and Smith,
2007
). Recently dated high flood deposits on the main Nile
are roughly coeval with sapropel units S6 (172 ka) and S3 (81 ka) (Williams et al.,
2010b
).
The most recent sapropel S1 in the eastern Mediterranean is a composite unit,
with ages of 13.7-12.4 ka near the base and 9.9-8.9 ka near the top (Williams et al.,
2010b
). The gap in the S1 record may coincide with the arid phase seen in other
parts of Africa coinciding with the Younger Dryas (around 12.5-11.5 ka). Higgs et al.
(
1994
) considered that formation of sapropel S1 may have ended as recently as 5 ka,
which is also when the Nile deep-sea turbidite system became inactive as a result
of reduced sediment discharge from that river (Ducassou et al.,
2009
). The interval
from around 13.7 to 8.9 ka and locally up to 5 ka also coincides with a time when
freshwater lakes were widespread in hollows between the White Nile dunes (Williams
and Nottage,
2006
), as well as west of the Nile and in the eastern Sahara (Williams
et al.,
1974
; Williams and Faure,
1980
; Pachur et al.,
1990
; Pachur and Hoelzmann,
1991
; Ayliffe et al.,
1996
; Pachur and Wunnemann,
1996
; Hassan,
1997
; Pachur and
Altmann,
1997
; Pachur and Hoelzmann,
2000
; Hassan et al.,
2001
; Hoelzmann et al.,
2004
; Williams et al.,
2010a
; Williams and Jacobsen,
2011
) and when the White Nile
attained flood levels up to 3 m above its modern unregulated flood level.
Where independently dated comparisons exist between sapropel formation and
Nile floods, they point to synchronism between sapropel accumulation and times of
higher Nile flow, indicative of a stronger summer monsoon at these times. Although
