The evolution of neogene terrestrial ecosystems in Europe

The Pliocene-Pleistocene chronology of hominid and other vertebrate evolution in East Africa is largely constrained by isotopic dating and regional intercorrelation of volcanic ash layers. Some eruptions were of sufficient magnitude or duration that their widespread tephra dispersal defines a series of dated marker horizons throughout the fossil-bearing sedimentary deposits of Tanzania, Uganda, Kenya, and Ethiopia (Brown, 1982; Feibel et al, 1989; Haileab&Brown, 1992,1994; Pickforderal, 1991; WoldeGabrieler al, 1994). Although many of the larger eruptive events have been dated directly the ages of many tephra are only constrained by indirect stratigraphic interpolation between dated levels. The geochcmica! compositions of volcanic glasses from each eruption are unique, providing a definitive means to establish broad tephrostratigraphic correlations linking the regional climatic, tectonic, and biologic histories of this distinctive archive of Earth history.