A mollusc thanatocenosis in the Nile River Valley near Wadi Halfa (N Sudan)

A mollusc thanatocenosis found in the Nile Valley on the shore of the Naser Lake contains several thousand specimens representing five species; shells of aquatic snails dominate. The coarse fraction is composed mainly of Cleopatra bulimoides (Olivier); the fine fraction – of Valvata nilotica Jickeli. Substantial differences between the mean size of mollusc shells and mineral grains in the thanatocenoses, reflected by the displacement index (DI), depend of the density (unit weight) of these components. Death assemblages deposited recently during floods resemble subfossil assemblages from Holocene deposits of the Fayum Depression (Egypt), thus testifying to the stability of the mollusc fauna inhabiting the Nile Valley during the last ten thousand years.