Abstract The upper Awash runs across a volcano-sedimentary succession dated from the Early to Middle Pleistocene and located on the western margin of the northern portion of the Main Ethiopian Rift. The succession lies above Late Miocene to Pliocene lava flows, domes and large volume ignimbrites. The succession formed within a fluvial system that developed within transversal rift faults. The stratigraphy consists of primary volcanic deposits interbedded with reworked sediments emplaced in a low-energy floodplain developed in a subsiding area. The lower part of the volcaniclastic sequence is dominated by a 1.2 Ma old, low aspect ratio, pyroclastic density current deposit (Kella ignimbrite). This eruption was followed by an eruptive stasis and reorganization of the drainage system. Tephra deposition in the floodplain climaxed again between 0.9 and 0.7 Ma and was associated with extensive tephra reworking. Sedimentation rates significantly decreased after 0.6 myr ago, probably owing to declining volcanic activity. Dynamic interaction between tectonics and volcanic activity created a complex sedimentary environment preserving numerous artefacts (lithic tools), animal and hominin remains. Stratigraphic correlation is based on the interpretation of the basin evolution and has relevance for the reconstruction of the palaeoenvironment and the interpretation of the palaeontological and archaeological data.

Abstract Some of the more important evidence is reviewed for the archaeology of hominin colonization associated with the Early-Middle Pleistocene transition. This is done by reference to the nature of migration ‘out of Africa’ before the interval of transition, across the transition itself, and then after it. Technologically assisted behaviour may not have been so important in the colonization process, behaviour and biology being the primary factors that led to the success of a migrating species. While climate change and especially shifts in local aridity would have been experienced and possibly remembered by localized hominin groups, the Acheulean behavioural repertoire did not change much across Africa and Europe over a million years of time. It merely adapted to local conditions. The Acheulean was a generalized hand-held processing technology for a generalized hominin.