Heritage Cases

As one of the principal investigators (together with Dr Guillaume Porraz, permit holder for the site) of the multidisciplinary project at Bushman Rock Shelter, I am applying here for a permit to export an ungulate tooth recovered from one of the Middle Stone Age layers to be dated in France using the U-series method. Dating the Middle Stone Age sequence at Bushman Rock Shelter is proving somewhat problematic using the luminescence method (i.e., significant discrepancy between OSL dates on quartz and on feldspar) and we would like to apply a different dating technique in order to overcome this problem. Our dating specialists in France, Dr Chantal Tribolo and Professor Norbert Mercier, are working in close collaboration with the IPREM-LCABIE Laboratory at the University of Pau, which hosts a femto-laser ablation system that can be used for measuring the Uranium and Thorium content of archaeological specimens. Refining the chronology of Middle Stone Age cultural, technological and behavioural developments in southern Africa is one of the current challenges faced by archaeologists (e.g. Jacobs et al., 2008; Lombard et al., 2012; Wadley, 2015). The Middle Stone Age, for most of it associated with Anatomically Modern Humans, starts somewhere before 250 000 BP and continues until 40-20 000 BP (Lombard et al., 2012). It experiences phases of apparent stasis and phases of apparent rapid innovations (i.e. traditionally, the Still Bay and the Howiesons Poort periods) but the exact tempo of these variations remains the topic of heated debates. One of the reasons behind the current disagreement regarding the beginning, end and length of some of the Middle Stone Age techno-complexes is the limited number of options available to archaeologists in terms of dating methods. Luminescence dating (Optically-Stimulated Luminescence –OSL- and Thermo-Luminescence) is the main dating option but is facing methodological shortcomings and seems to experience great discrepancies from one lab to another (see for instance: Jacobs et al., 2008; Tribolo et al., 2013; Guérin et al., 2013; Porraz et al., 2018; de la Peña et al., 2018). Combining luminescence dating with other dating techniques is therefore critical. At Bushman Rock Shelter, the end of the Middle Stone Age sequence has so far only been dated using OSL on quartz and on feldspar. Unfortunately, a gap of ca. 20 000 years is observed for the upper two phases dated respectively to 71 and 75 000 BP using the quartz grain OSL method and 91 and 95 000 BP using the feldspar one (Porraz et al., 2018). This year, we have uncovered several dental remains in one of the layer from the site consistent with the latest part of the Middle Stone Age sequence (phase “21”). This offers the opportunity to try another method, namely U-series, on one of the teeth, in order to clarify the chronology of the archaeological sequence from the site.