New Oldowan localities at high level within Kilombe Caldera, Kenya

New occurrences of early artefacts ascribed to the Oldowan tradition come from localities at high level within the caldera of the extinct Kilombe volcano, located in the central rift valley of Kenya. The trachyte cone and caldera of Kilombe volcano formed at ca. 2.5 Ma, and the record of >130m of sediment-fill indicates that the caldera subsequently held a lake for long periods during the Early Pleistocene. The Oldowan artefact localities, dated by 40Ar/39Ar and palaeomagnetism to ∼1.78 Ma, lie east of the centre of the caldera, on the west side of an ancient small lake, which later drained away as a gorge formed on the east side of the mountain. The artefacts are dominantly made of Kilombe trachyte, and are associated with a fauna of large animals including Hippopotamus gorgops. These are the first Oldowan localities to be discovered in a new area of the Kenyan rift valley in the last thirty years, and their presence at high level in rugged landscape indicates that the associated hominins were exploiting a full range of environments.