Using Radiometric Dating, Magnetostratigraphy, and Tephrostratigraphy to Calibrate Rates of Hominin Evolution in the East African Rift

Age-calibration of hominin fossils and artifacts in the East African Rift is principally achieved through dating of associated volcanic-sedimentary strata. The dominant dating techniques for sites >100 ka are the 40Ar/39Ar radiometric dating method, magnetostratigraphy, and tephrostratigraphy. The 40Ar/39Ar technique relies on the occurrence of volcanic deposits in the target strata, which are often present as a consequence of the interplay of rift formation and volcanic activity. The frequency of datable material may be limited; however, by also applying the relative dating methods of magnetostratigraphy and tephrostratigraphy to these same strata, a chronostratigraphic framework can be built and applied to fossiliferous strata. This chapter provides examples of the application of these techniques at Olduvai Gorge, Tanzania, and two areas of the East African Rift in Ethiopia.