Strontium isotope evidence for late Pleistocene reestablishment of an integrated Nile drainage network

Evidence of late Pleistocene closed-basin conditions in equatorial African lakes has far-reaching implications for the history of the Nile River. Ther e has been widespread acceptance that overflow of Lakes Victoria and Albert into the Nile occurred some time during the terminal Pleistocene, but rece nt suggestions that Lake Victoria remained a closed basin until ca. 7.2 ka imply a much longer period of greatly reduced White Nile discharge. This hy pothesis has major consequences for current ideas about the river's paleohy drology, early human exploitation of riverine resources, Nile delta sedimen tation, and late Quaternary genesis of sapropels in the eastern Mediterrane an. Here we resolve the timing of Lake Victoria's overflow by using stronti um isotopes as a tracer for water from the principal lakes and rivers of th e Upper Nile. Our data demonstrate that overflow of Lakes Victoria and Albe rt into the Nile drainage network occurred no later than 11.5 C-14 ka.