Kobo 1 and L'Abri aux Vaches (Mali, West Africa): Two case studies for the optical dating of bioturbated sediments

The purpose of the study was to provide further chronological data for the microlithic assemblages in the region of the Dogon Country (Mali). In two sites, Kobo 1 and L'Abri aux Vaches, the absence of any characteristic material could not help in concluding whether the microliths were of Pleistocene or Holocene age. Radiocarbon dating failed because the analysed charcoals appeared to have been introduced following recent bioturbation. These were visible in the archaeological sections and therefore, an attempt at dating with single-grain optically stimulated luminescence was made. After discussing the appropriate way of applying the Finite Mixture Model, we are able to conclude that the sediments containing the microliths from L'Abri aux Vaches were deposited during the beginning and the middle of the Holocene period (13.5 +/- 1.0 and 5.9 +/- 0.4 ka). For Kobo 1, the analysis reveals extensive bioturbation, precluding the obtaining of any reliable result. (C) 2009 Elsevier B.V. All rights reserved.