Tracing the Source of the Elephant And Hippopotamus Ivory from ...

and water and sediment from the Nile. The four main sources of the Nile include the
Atbara, Sobat, and the Blue Nile, all of which hail from monsoonal rainfall over the
Ethiopian highlands, and the White Nile which originates from Lake Victoria in the
Central African Plateau.
At present the Blue Nile and Atbara contribute 97% of the sediment load of the
Nile, and these sediments derive from the weathering of Tertiary basalts in the Ethiopian
Highlands. The White Nile on the other hand only contributes 3% of the sediment load.
Aeolian Saharan dust from Paleozoic Nubian sandstones and Cretaceous rocks of the
North Africa desert belt mixes with the sediment load of the Nile to form the surface
sediments of the eastern Mediterranean (Schilman et al. 2001: 171).
The researchers found that the relative contribution of aeolian dust and Nile
sediments changed with time, reflecting an aridification trend in the eastern
Mediterranean. This aridification process included the reduction of vegetation cover in
East Africa, which in turn “led to an increased erratic flood-related sediment flux via the
Nile River... This is reflected by the general change in the local sediment composition. At
3.6 ka, the Saharan eolian input reached 65% whereas at about 0.3 ka 70% of the SE
Mediterranean sediment was composed of Nile particulate matter” (Schilman et al. 2001:
157; see also Abell and Williams 1989). Thus, from Figure 54, the surface sediment
composition circa 1300 B.C. may be roughly extrapolated as 40% Nile sediments and
60% Aeolian dust. The modern predominance of Nile sediment in the surface sediments
of the eastern Mediterranean was also discussed by Waldeab et al. (2002). They found
the surface sediments of the eastern Mediterranean to exhibit the lowest 87 Sr/ 86 Sr values
(average 0.709541) of the entire Mediterranean, which reflected the input of the Nile
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