Molluscan Assemblages from the Late Cenozoic of the Lower Omo Basin, Ethiopia

Abstract
The lower Omo basin, southern Ethiopia, preserves formations of sedimentary and pyroclastic rocks which span a substantial range of later Cenozoic time. These formations are often extraordinarily rich in vertebrate fossils and have also afforded a series of molluscan assemblages from contexts radiometrically dated by K/Ar or 14C. The late Cenozoic molluscan fauna has been previously ill-known in this part of Africa and these assemblages provide a broad faunal zonation for the northern sector of the Eastern Rift valley. The five principal assemblages are here treated as faunal groupings, rather than as formal faunal zones. Three groupings are recognized for the Pliocene/Pleistocene time range, one grouping for the later Pleistocene and one grouping for the subrecent and present.