الملخص

Th age of the thick succession of 500m conglomerate and red claystone layers in the incised valleys at the lower part of Tanjero Formation at Chwarta area is estimated to be (1.23 m.y) duration. The age determination is achieved by Planktonic Foraminiferal biostratigraphic zonation which included the following Zones: Globotruncana aegyptiaca Interval Zone (CF8), Gansserina gansseri Interval Zone (CF7) Racemiguemblina fructicosa Interval Zone (CF4), Pseudoguembelina hariaensis Interval Zone (CF3) with missing zones of Contusotruncana contusa Interval zone (CF6) and Pseudotextularia intermedia Interval zone (CF5). Twenty six planktonic foraminiferal species and thirty benthonic foraminiferal species assigned to 33 genera have been recorded. The zonal scheme developed here is correlated with other sequences of Li and Keller (1998a) and d iscussed. e