Chronology of the earliest peopling of the Ethiopian highlands at Melka Kunture pre-dating the 1.925 Ma base of the Olduvai subchron

Abstract

Melka Kunture on the highlands of Ethiopia has provided evidence for the early peopling of the Ethiopian highlands (>2000 m asl). At site Garba IV, an Oldowan technocomplex was retrieved in levels E-F located shortly below the base of the Olduvai subchron, with a currently accepted age of 1.925 Ma, while the early Acheulean was found in level D located close to the base of the Olduvai subchron. The base of the Olduvai subchron becomes therefore a prime chronostratigraphic marker for the study of the early peopling of the Ethiopian plateau in the Early Pleistocene. Here we report new magnetostratigraphic data from two sections from the Kella valley located close to Garba IV, namely Kella III bis and Kella Bridge. We document in these sections the occurrence of the Olduvai subchron, confirmed also by 40Ar/39Ar ages from the literature. We correlate these new data to previous data from Garba IV, establishing a robust registry of the critical Olduvai subchron in the lower part of the Middle Succession (part of the former Melka Kunture Formation), spanning altogether from ∼2 Ma to ∼1.2 Ma, and we also point to a regional basal unconformity marking its onset of deposition. The better constrained magnetochronology provides firm evidence that hominins were peopling areas at 2000 m of altitude at least 2 million years ago.