Radiometric dating and tuff mineralogy of omo group deposits

Through the efforts of the Omo Research Expedition and the East Rudolf Research Group, a large number of vertebrate fossils have been collected from the sedimentary deposits near the northern end of Lake Rudolf in Kenya and in the lower Omo valley in Ethiopia. The hominid fossils collected in this area have attracted the most attention, but the associated mammalian fossils are of equal importance, since they provide clues to the environment in which early man lived. Because these large collections of well-preserved material are extremely useful for correlation and for ascribing ages to other deposits, dating them is critical. In this chapter we try to describe some of the problems encountered in dating the deposits in the lower Omo valley, to assess some of the possible problems, and where possible to apply other controls to the radiometric dates. The work is not yet finished, and it may be many years before the final words are written on the age of these deposits. The following text is merely a summary of our knowledge to date.