Guy Kieffer

Obsidian exploitation and utilization during the Oldowan at Melka Kunture (Ethiopia)

The Oldowan assemblages of Melka Kunture represent the earliest known example of obsidian utilization. The proximity of primary and secondary sources of Balchit obsidian, a high quality raw material easily available in large quantities, is a unique situation among East African Oldowan sites. Obsidian represents a large component of the lithic assemblages at Melka Kunture, not only during the Oldowan but during the Acheulian times as well. Other volcanic rocks are incorporated into the technological system at Melka Kunture such as basalts, ignimbrites, trachytes and trachybasalts, which present completely different characteristics for knapping.

Hypothèse d'un processus de glissement sur le secteur nord-est de la caldera de Las Canadas del Teide (Tenerife, Canaries, Espagne) : arguments géophysiques et morpho-structuraux

Abstract The Las Canadas caldera is a 15 km broad depression. Its origin is always discussed: (i) collapsing, (ii) graben sector slipping, (in) erosion. The present contribution concerns the knowledge of the upper filling, in relation to the internal structure of the caldera. Under certain conditions, Self-Potential measurements (SP method) allow us to calculate a two-layer model; the first one being the unsaturated zone overlapping the second, saturated zone or impermeable substratum. From these measurements, we suggest the possibility of a collapsing process in the southern part of the caldera, but graben sector slipping in the northern-east zone.