Heritage Cases

To develop a highly resolved sequence, we sampled the section intensively for single grain optically stimulated luminescence (OSL) dating tied to piece-plotting of every find by total station. We now have over 90 OSL ages under analysis or finalized and over 400,000 plotted finds, with the sampled sediments dating between ~90-50 ka from over 15 vertical m of MSA deposits. A major goal of our excavations at PP5-6 has been to sample the later phases of marine isotope stage 5 through 3, and thus create a composite continuous temporal sequence for the south coast based at PP. PP13B has a sequence dating between 164 ka to 90 ka, at which time it was sealed from occupation by a dune abutting the cliff. Given the ages of PP5-6, we have now achieved that goal. We have provided published descriptions of PP5-6 (Brown et al 2009; Brown et al 2012; Karkanas et al. 2015; Smith et al. 2018), and each of these publications includes lengthy descriptions of the archaeological materials. We just published a paper in Nature (Smith et al. 2018) that reported on the discovery of tephra shards from the Indonesian volcano of Toba in the PP5-6 sediments, and in that paper we published an age model for the site that included a Bayesian statistical analysis of 90 OSL ages. Importantly, the location of the ~74 Toba eruption was in sediments predicted by the OSL age model to date to between 75-73 ka, thus providing outstanding confirmation of the accuracy and precision of our model. Specific Goals 1) MSA sediments in PP5-6 South Area were revealed by a small test excavation. We think, for geological reasons, that these MSA sediments may be of MIS5e age, or possibly even MIS6 or older. If so, these sediments will be of extraordinary significance since sediments of these ages are rare in the South African MSA record. Therefore, we targeted them and the layers above for OSL dating. 2) Excavations in 2016 and 2017 at PP5-6 North Area revealed a deeper and more complex sequence in the BAS and BBCSR stratigraphic aggregates than had previously been excavated. Our OSL age model has a very small sample from the BAS, and while we have a good range of ages from the BBCSR, we revealed layers in 2016 and 2017 that were disoconnected horizontally from those previously sampled. We therefore targeted these layers for more OSL dating. 3) Excavations in 2016 and 2017 at PP5-6N provided an improved section spanning the MIS5-4 transition, which is a critical climate, environment, and behavioral-cultural transition across Africa. We therefore targeted this stratigraphic zone for denser dating to improve the resolution of our age model. This is reflected in the new samples from upper LBSR, ALBS, and SADBS stratigraphic aggregates. 4) Excavations in 2016 and 2017 at PP5-6N provided an improved section and preservation of layers within MIS4 that sit above the SADBS where the earliest microliths are found (Brown et al. 2012) and below the classic Howiesonspoort. These layers are in the stratigraphic aggregate called the SGS. We therefore targeted these layers for more OSL dating. 5) Finally, the entire PP5-6N area is heavily truncated by a gulley that has a cut and fill sequence. This sequence holds clues to the preservation and destruction of portions of the site. We therefore targeted these layers for OSL dating.