New radiometric data have recently been acquired on basalt and rhyolite sampled at various levels of the volcanic sequence occurring in the central Eritrean plateau, confirming the stratigraphic reconstruction suggested in a previous paper [Zanettin, B., Bellieni, G., Justin Visentin, E., Haile, T., 1999. The volcanic rocks of the Eritrean plateau: stratigraphy and evolution. Acta Volcanologica 11(1), 183193]. New considerations indicate the tholeiitic, not alkaline, nature of the Asmara basalt. Doubts about the relative age of the Aiba/Alaji and Asmara basalts have now been clarified: they are, at least partly, coeval (about 30 Ma old). The Serae rhyolite intercalated in the Adi Ugri basalt turns out to be about 24 Ma old, like the more abundant ignimbrite outcropping in the Senafe area, of which it is the westernmost extension. Its age confirms that it does not correspond to the trachyte intercalated in the Oligocene stratoid basalt of the Adwa-Axum area (where the Adi Ugri basalt probably also occurs, intercalated with the Serae trachyte and rhyolite). The upper part of the Adi Ugri basalt is 22 Ma old (an age consistent with the finding of a Deinotherium tooth). The radiometric age of these rocks also confirms already indicated correlations between Eritrean and Ethiopian volcanic formations.
New radiometric age of volcanic rocks in the central Eritrean plateau (from Asmara to Adi Quala): Considerations on stratigraphy and correlations.
Bellieni G;
2006
Abstract
New radiometric data have recently been acquired on basalt and rhyolite sampled at various levels of the volcanic sequence occurring in the central Eritrean plateau, confirming the stratigraphic reconstruction suggested in a previous paper [Zanettin, B., Bellieni, G., Justin Visentin, E., Haile, T., 1999. The volcanic rocks of the Eritrean plateau: stratigraphy and evolution. Acta Volcanologica 11(1), 183193]. New considerations indicate the tholeiitic, not alkaline, nature of the Asmara basalt. Doubts about the relative age of the Aiba/Alaji and Asmara basalts have now been clarified: they are, at least partly, coeval (about 30 Ma old). The Serae rhyolite intercalated in the Adi Ugri basalt turns out to be about 24 Ma old, like the more abundant ignimbrite outcropping in the Senafe area, of which it is the westernmost extension. Its age confirms that it does not correspond to the trachyte intercalated in the Oligocene stratoid basalt of the Adwa-Axum area (where the Adi Ugri basalt probably also occurs, intercalated with the Serae trachyte and rhyolite). The upper part of the Adi Ugri basalt is 22 Ma old (an age consistent with the finding of a Deinotherium tooth). The radiometric age of these rocks also confirms already indicated correlations between Eritrean and Ethiopian volcanic formations.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
