True colours: analysing apparent sedimentary divisions in the stratigraphic sequence of Umhlatuzana rockshelter (South Africa) using Munsell-based colour determinations

NWOVidi 276-60-004Human Origin

Past and present: raw material identification approaches at Umhlatuzana rockshelter, South Africa

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 - 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.NWOVidi 276-60-004Human Origin

Past and present: raw material identification approaches at Umhlatuzana rockshelter, South Africa

NWOVidi 276-60-004Human Origin

Integrating geoarchaeological techniques to reveal the invisible stratigraphy at Umhlatuzana rockshelter, South Africa: a grid-based approach

Umhlatuzana rockshelter is an archaeological site with an occupational record spanning the last ~70,000 years, covering the Middle Stone Age (MSA), Later Stone Age (LSA), and Iron Age. The deposits bearing Pleistocene archaeological assemblages at Umhlatuzana rockshelter appear homogeneous with no macroscopically visible stratigraphic boundaries. This means the integrity of the archaeological assemblages is difficult to ascertain. Moreover, the sedimentation rate, taphonomic history, and the environmental context across the sequence are unclear. This study aims to resolve these issues by integrating different geoarchaeological techniques in order to explore fine-resolution geochemical differentiations of the sediments that are macroscopically invisible. Samples were systematically retrieved from the western profile of the site following a grid-based sampling strategy and analysed for pH, elemental composition (XRF), and Magnetic Susceptibility. These methods were chosen because they provide insight into ‘invisible’ geoarchaeological dynamics, related to sediment input (geogenic and anthropogenic), taphonomy, and environmental conditions. Additionally, the results were integrated with preliminary micromorphological observations. Our study reveals a gradual change in the geochemistry of the deposits throughout the Pleistocene, related to a combination of environmental change and occupation intensity. Furthermore, the gradual change within the geochemical data indicates that no large-scale sediment mixing took place (contrary to previous suggestions), while small-scale mixing related to bioturbation is visible in the micromorphological thin sections. Our study offers a successful multi-proxy approach to systematically sample and analyse archaeological deposits at the macro and micro scale, integrating a variety of geoarchaeological techniques. The approach provides insight into the depositional and postdepositional history of the site, and allows questions of stratigraphic integrity, anthropogenic input, preservation, and environmental change to be addressed.NWOVidi 276-60-004Human Origin

Making the invisible stratigraphy visible: a grid-based, multi-proxy geoarchaeological study of Umhlatuzana rockshelter, South Africa

Umhlatuzana rockshelter is an archaeological site with an occupational record covering the Middle Stone Age, Later Stone Age, and Iron Age. The presence of both Middle and Later Stone Age assemblages makes Umhlatuzana the ideal location for the study of the MSA-LSA transition (20-40 ka) in southern Africa. This transitional period is characterized by important modifications in stone tool technology, from prepared core technology to a toolkit based on microlith production. These changes are argued to have occurred in response to changes in climate and environment leading up to the Last Glacial Maximum. The deposits bearing the transitional assemblages at Umhlatuzana rockshelter appear homogeneous with no visible stratigraphic boundaries. This study integrates geoarchaeological techniques in order to explore fine-resolution geochemical differentiations of the sediments that are macroscopically invisible, and that will provide insight into (post-)depositional processes over time. Samples were systematically retrieved from the western profile of the site following a grid-based sampling strategy and analyzed for pH, elemental composition (XRF), and Magnetic Susceptibility. Additionally, the results were integrated with preliminary micromorphological observations. Our study reveals a steady, gradual change in the geochemistry of the deposits throughout the Pleistocene, related to a combination of environmental change and occupation intensity. We suggest that the part of the sequence reported to bear Middle to Later Stone Age transitional industries is characterized by wetter environmental conditions compared to the underlying deposits. Additionally, we support results from previous studies that excluded large scale post-depositional movement of the sedimentary sequence. Our study offers a successful multi-proxy approach to systematically sample and study archaeological deposits at the macro and micro scale, integrating a variety of geoarchaeological techniques. The approach provides insight into the depositional and post-depositional history of the site, and allows for questions of stratigraphic integrity, anthropogenic input, preservation, and environmental change to be addressed.Thrombosis and Hemostasi

Data-mining quartz and quartzite: should we have standard protocols for measuring and reporting on lithic assemblages?

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-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. NWOVidi 276-60-004Human Origin

How to deal with homogeneous stratigraphies: excavation, sampling, and analysis strategies at Umhlatuzana Rockshelter, Kwazulu-Natal, South Africa

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. 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. NWOVidi 276-60-004Human Origin

Making the invisible stratigraphy visible: a grid-based, multi-proxy geoarchaeological study of Umhlatuzana Rockshelter, South Africa

Umhlatuzana rockshelter is an archaeological site with an occupational record covering the Middle Stone Age, Later Stone Age, and Iron Age. The presence of both Middle and Later Stone Age assemblages makes Umhlatuzana the ideal location for the study of the MSA–LSA transition (20–40 ka) in southern Africa. This transitional period is characterized by important modifications in stone tool technology, from prepared core technology to a toolkit based on microlith production. These changes are argued to have occurred in response to changes in climate and environment leading up to the Last Glacial Maximum. The deposits bearing the transitional assemblages at Umhlatuzana rockshelter appear homogeneous with no visible stratigraphic boundaries. This study integrates geoarchaeological techniques in order to explore fine-resolution geochemical differentiations of the sediments that are macroscopically invisible, and that will provide insight into (post-)depositional processes over time. Samples were systematically retrieved from the western profile of the site following a grid-based sampling strategy and analyzed for pH, elemental composition (XRF), and Magnetic Susceptibility. Additionally, the results were integrated with preliminary micromorphological observations. Our study reveals a steady, gradual change in the geochemistry of the deposits throughout the Pleistocene, related to a combination of environmental change and occupation intensity. We suggest that the part of the sequence reported to bear Middle to Later Stone Age transitional industries is characterized by wetter environmental conditions compared to the underlying deposits. Additionally, we support results from previous studies that excluded large scale post-depositional movement of the sedimentary sequence. Our study offers a successful multi-proxy approach to systematically sample and study archaeological deposits at the macro and micro scale, integrating a variety of geoarchaeological techniques. The approach provides insight into the depositional and post-depositional history of the site, and allows for questions of stratigraphic integrity, anthropogenic input, preservation, and environmental change to be addressed. NWOVidi 276-60-004Human Origin

New Excavations at Umhlatuzana Rockshelter, KwaZulu-Natal, South Africa: a Stratigraphic and Taphonomic Evaluation

Umhlatuzana rockshelter has an occupation sequence spanning the last 70,000 years. It is one of the few sites with deposits covering the Middle to Later Stone Age transition (~40,000–30,000 years BP) in southern Africa. Comprehending the site’s depositional history and occupation sequence is thus important for the broader understanding of the development of Homo sapiens’ behavior. The rockshelter was first excavated in the 1980s by Jonathan Kaplan. He suggested that the integrity of the late Middle Stone Age and Later Stone Age sediments was compromised by large-scale sediment movement. In 2018, we initiated a high-resolution geoarchaeological study of the site to clarify the site formation processes. Here, we present the results of the excavation and propose a revised stratigraphic division of the Pleistocene sequence based on field observations, sedimentological (particle size) analyses, and cluster analysis. The taphonomy of the site is assessed through phytolith and geochemical (pH, loss on ignition, stable carbon isotope) analyses. The results indicate a consistent sedimentological environment characterized by in situ weathering. The analysis of the piece-plotted finds demonstrates semihorizontal layering of archaeologically dense zones and more sterile ones. There was no indication of large-scale postdepositional sediment movement. We show that the low-density archaeological horizons in the upper part of the Pleistocene sequence are best explained by the changing patterns of sedimentation rate