Introduction

According to the definition of the lower boundary of the Pleistocene epoch at Vrica (Pasini and Colalongo, Chapter 2, this volume), the top of the Olduvai subchron can be used as a convenient approximation of the Quaternary boundary in nonmarine areas. In Africa, several highly fossiliferous stratigraphic sequences are known in which the limits of the Olduvai subchron can be placed, either by direct paleomagnetic observations or through good radiometric control. The faunal associations in those sequences can then be used for correlating other deposits in which paleomagnetic or radiometric age data are not available. The major sequences with geochronological control are in East Africa, whereas the occurrences in southern (and northern) Africa are generally deficient with regard to isotope age determinations and paleomagnetic data.

East African Plio–Pleistocene deposits

The highland areas of East Africa, including Ethiopia, have been strongly affected by tectonic and volcanic activity since at least the early Miocene, and the rift valleys and downwarped areas have provided unusually good traps for the accumulation of fossil-bearing sediments, in many cases associated with lavas or volcanic tuffs that furnish radiometric or fission-track ages. Geochemical “fingerprinting” of tuffs has also been employed successfully as a correlation tool. The broad geological framework has been described by a number of specialists, and the fossil mammals have been treated extensively (Maglio and Cooke, 1978).