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

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Figure 55: Contour diagrams for <strong>the</strong> isotopic composition <strong>of</strong> lithogenic surface sediments<br />

in <strong>the</strong> eastern Mediterranean. Contours are drawn at intervals <strong>of</strong> 0.001<br />

(Weldeab et al. 2002: 145, figure 4b).<br />

Thus <strong>the</strong> average input to <strong>the</strong> eastern Mediterranean circa 1300 B.C. was approximately<br />

0.71589. This is only an estimate because modern values for Nile sediment and Saharan<br />

dust were used, and moreover Pe-Piper and Piper (2001) cite slightly higher modern Nile<br />

sediment values <strong>of</strong> 0.7075 to 0.7078.<br />

Gerstenberger et al. (1997) address <strong>the</strong> origin <strong>of</strong> strontium in <strong>the</strong> Nile, tracing <strong>the</strong><br />

major fluvial inputs, <strong>the</strong>ir sources, and <strong>the</strong> sources <strong>of</strong> change to <strong>the</strong> strontium signature<br />

during <strong>the</strong> course <strong>of</strong> <strong>the</strong> rivers. As mentioned previously, <strong>the</strong> Blue Nile, Atbara, and<br />

Sobat drain <strong>from</strong> <strong>the</strong> Ethiopian highlands which are geologically characterized by<br />

oceanic crustal rocks. As a result, <strong>the</strong> strontium content <strong>of</strong> <strong>the</strong>se rivers bears an old<br />

oceanic crustal signature <strong>of</strong> relatively higher 87 Sr/ 86 Sr values. The White Nile drains<br />

<strong>from</strong> a large area <strong>of</strong> supracrustal metamorphic rocks with even higher strontium isotope<br />

ratios, including <strong>the</strong> Lake Victoria plateau and Bahr el Ghazal region. However, it is also<br />

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