Lithology, dynamism and volcanic successions at Melka Kunture (Upper Awash, Ethiopia)
Résumé
The volcanism fossilised and conserved the Melka Kunture prehistoric sites. The depression, created upstream of the Awash village sill and maintained by the tectonic reactivation of the fault system that constitutes the south-south-east border, provided a choice receptacle for the volcanic materials. Except for the products of the initial autochthonous manifestations, the latters came from volcanoes distant by several kilometres and up to several tens of kilometres. The volcanoes were mostly explosive, as indicated by the differentiated nature of the magmas. In multiple phases of activity, since 4 or 5 million years ago, they have mainly emitted pyroclastites. A good quantity arrived directly on the sites, particularly the various welded or non-welded ignimbrites but also numerous aerial ashy and pumiceous fallouts, from repeated phreato-magmatic blows, whose destructive strength is well known. The periods of human occupation, less than 2 Ma old, are posterior to the large eruptions that produced the wide sheets of welded ignimbrites. Such occupations were however disturbed by the very violent eruptions that have on several occasions, completely erased any evidence of the existence of hominids along the Awash River, particularly those of non-welded ignimbrites. The several tuff layers identified in the Gombore-Garba series support the simple model previously established. Moreover, correlations between localities are difficult to establish due to lateral variations in facies and geochemistry of tephras. A preliminary synthesis is proposed.
Loading...