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

Figure 56: The Sr isotope ratios in the water of the Nile from Aswan to North of Cairo
(gray ovals) (Gerstenberger et al. 1997: 354, figure 2).
of 0.7117 at Bor. Farther downstream, the Sobat empties into the White Nile, effecting
lower Sr ratios at Esh Shawal, Guli and Tagra of 0.7093 to 0.7109 (determined from
fossil mollusks and faunal remains). The Sobat probably has values similar to the Gezira
region of the Blue Nile (0.7062), as the both empty from the volcanic geology that is the
Ethiopian highlands. See Figure 57 for a map of this region and locations of sampled
fossils, and Figure 58 for a schematic diagram of strontium ratio values during the course
of the White Nile.
Ethiopia
Having considered the hydrology of the Nile, and in particular its catchment
areas, I shall now turn to the geology of Ethiopia. Fortunately there is a great deal of
144