To ensure proper context control for archaeological samples, it is crucial that excavations determine and,where possible, follow the natural stratigraphic subdivisions in a sedimentary sequence.... Show moreTo ensure proper context control for archaeological samples, it is crucial that excavations determine and,where possible, follow the natural stratigraphic subdivisions in a sedimentary sequence. In cases with a single,unchanging source of sedimentary input, this may pose challenges. We present our strategies to deal with a>2 m deep homogeneous Pleistocene stratigraphy at Umhlatuzana rockshelter in South Africa, yieldingarchaeological remains from the Middle Stone Age. The site was originally excavated during a rescue project in 5–10 cm deep artificial spits for lack of visible stratigraphy. We revisited the shelter in 2018 and 2019. We integrate current standard practice such as piece-plotting archaeological materials with digital methods such as cluster analysis and geoarchaeological analyses (e.g., micromorphology, sedimentological analyses, geochemical analyses) to track the different sources of sedimentary input. We also develop an intensive sediment sampling strategy to illuminate geochemical variation within the sequence and postdepositional alterations affecting preservation conditions. We manage to reconstruct a natural stratigraphy of the site combining these methodologies, resulting in a radically changed understanding of the stratigraphy, depositional environment, and mechanisms of postdepositional disturbance. Show less
Schmid, V.C.; Sifogeorgaki, I.; Dusseldorp, G.L.; Chu, W. 2023
Raw materials are the lowest common denominator of any debitage analysis. And yet, the fracture mechanicsof eccentric raw materials are not always fully considered when performing inter-/intra... Show moreRaw materials are the lowest common denominator of any debitage analysis. And yet, the fracture mechanicsof eccentric raw materials are not always fully considered when performing inter-/intra-assemblagecomparisons. The fracture mechanics as one constraint to be respected by the knappers greatly influencearchaeological recovery of debitage products in different raw materials. Thus, our methodologies forrecording debitage morphometrics may need to be adapted to specific raw materials. This means assemblagecomparison and correlation can only be attempted in a context-dependent manner. We review results ofassemblages in both chert and other raw materials from a range of locations across Old World to examinehow such assemblages have been recorded. In doing so, we highlight various pitfalls and limitations, andpropose that it is very important to provide the contextual information and describe exactly what methodwas used and give arguments, why it was used. Show less
Umhlatuzana is an important archaeological site for the study of the Middle and Pleistocene Later Stone Age in South Africa with a largely continuous occupation sequence spanning MIS 4-2 (~70,000 -... Show moreUmhlatuzana is an important archaeological site for the study of the Middle and Pleistocene Later Stone Age in South Africa with a largely continuous occupation sequence spanning MIS 4-2 (~70,000 - 10,000 BP). The main technocomplexes represented are Still Bay, Howiesons Poort, Sibudan, final MSA and Robberg (from old to young). Changing selection of raw materials is an important issue in the study of the Middle-to-Later Stone Age transition that appears characterised by a shift in raw material use in addition to a technological organisation. Umhlatuzana was first excavated in 1975 by Jonathan Kaplan who suggested that the lithic assemblage of the Pleistocene deposits consisted mainly of quartz (61%), hornfels (37.6%), and quartzite (1.4%) (Kaplan 1990). Renewed excavations at the site were conducted during 2018 and 2019. This campaign aims to clarify the site’s formation processes employing micromorphological analysis and other techniques (Reidsma et al. 2021, Sifogeorgaki et al. 2020). Micromorphology uses thin sections of undisturbed sediment samples for microscopic studies. The sections allow a petrological inspection of rock fragments embedded in the deposits. Rather unexpectedly, the Umhlatuzana thin sections yield different raw material determinations than Kaplan (1990). While quartz and hornfels are present (around 23% and 25% respectively), they represent a much less sizable proportion than previously reported. Instead, the most prominent raw material observed is a quartz arenite sandstone (42%). Quartzite fragments were not detected.We therefore initiated an in-depth mineralogical and elemental classification of the raw materials. We distinguish 6 raw material types based on the thin section analysis: sandstone, quartz, hornfels, dolerite, chert and diorite. We then determined the elemental composition of the raw material types of the micromorphology samples using p-XRF. Additionally, p-XRF analysis was conducted on c. 100 specimens from the 2018-2019 excavation lithic collection. This allowed us to determine elemental characteristics of the raw materials used during the Pleistocene occupation of the site. Subsequently, p-XRF analysis was systematically performed on a larger sample set of lithics from the site in order to correctly determine their raw material type. The combination of micromorphological and p-XRF analysis of the Umhlatuzana assemblages demonstrates that if only visual inspection is done, the variability of raw materials used may be misinterpreted and the relative frequency of different rock types in an assembly may be over- or underestimated. Future work will aim at re-visiting the raw material categorization of artefacts excavated during the 1975 excavations. Show less
