Paper short abstract:

Chesowanja (Lake Baringo, Kenya) has along Pleistocene record including Oldowan and Acheulean artefact layers. We report on recent field investigations yielding new Acheulean bifaces and new dating of the Chesowanja basalt previoulsy reported as 0.7 Ka and 1.4 Ma in the 1970s.

Paper long abstract:

Chesowanja lies on the east side of Lake Baringo, Kenya. Its Pleistocene sites lie on a fault step to the east of Lake Baringo. The long Pleistocene record is laid out almost horizontally, running from earliest localities in the west to latest in the east, across a distance of about 1 km. Chesowanja was studied in the 1970s within the EAST African Geological Research Unit programme (EAGRU), and its archaeology was investigated at that time and subsequently. The oldest formation is the Chemoigut, consisting of clays and silts associated with mammal fauna, remains of Australopithecus boisei, and archaeological remains which were attributed to the Developed Oldowan. The Chemoigut Formation was originally capped by a flow of basalt, which has largely eroded away. The basalt makes up the lower part of the Chesowanja Formation, which is associated with Acheulean artefacts and some fossil fauna. Later archaeology, including pastoral Neolithic, is represented further east in and around a former course of the Mukutan river. We report on a reassessment of the Chemoigut and Chesowanja Formation industries following further investigation which has yielded new Acheulean bifaces. The age of the Chesowanja basalt has been in doubt since seemingly conflicting dates of 0.7 Ka and 1.4 Ma were published in the 1970s. We report new Ar-Ar dating evidence which contributes to dating the whole sequence.