New dates from the Ethiopian plateau volcanics

Abstract

INTERPRETATION of geological events in Ethiopia has been severely limited by the lack of isotopic age data from the plateau volcanics. Volcanism was thought to have begun in the Eocene—an idea based chiefly on ages from the Blue Nile Gorge basalts1. These basalts have been resampled and ages of 23 to 27 Myr determined2. Recent research involving the measuring and sampling of volcanic profiles on the Western and South Eastern Ethiopian Plateaus, has made it possible to sample the basal flows which immediately overlie Mesozoic sediments. We report here nine new K–Ar dates from the Mugher, Adigrat, Garamullatta, and Jijiga profiles (Fig. 1.) The data are presented in Table 1 together with brief petrographic descriptions. All samples contain up to 12 % intersertal glass; whole rock samples were analysed. The errors quoted are at the 60% confidence limit and based on replicate analyses.