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

Abstract

A lateral offset in sediment colour in the Pleistocene archaeological sequence of Umhlatuzana has been interpreted as representing large-scale sediment movement (Kaplan 1990). Renewed excavations suggest the archaeological materials are in situ based on multiple lines of evidence (Sifogeorgaki et al. 2020). We analyse the sediment colour from samples across the Umhlatuzana sequence in laboratory conditions to demonstrate homogeneous colour of the materials comprising the sequence. We interpret the observed colour difference in the Pleistocene deposits as the result of the site’s hydraulic environment.

Sand, hearths, lithics and a bit of bioturbation: Site formation processes at Umhlatuzana rockshelter, South Africa

“…Moreover, the geochemistry of the Pleistocene sediments (XRF, pH, magnetic susceptibility) shows gradual changes (Reidsma et al, 2021), and preliminary micromorphological results did not find evidence indicating large-scale movement (Reidsma et al, 2021). The colour difference between the sediments is only related to moisture differences (Sifogeorgaki & Dusseldorp, 2022).…”

“…1. Group P deposits appear homogeneous in colour apart from the lower south area where the deposits have a darker colour due to higher moisture content (Sifogeorgaki & Dusseldorp, 2022). This is attributed to seeping water flow from the rockshelter's wall.…”

“…The newly excavated western profile was documented in detail and sampled for various analyses. Geoarchaeological and paleoenvironmental results were presented by Sifogeorgaki et al (2020), Reidsma et al (2021) and Sifogeorgaki and Dusseldorp (2022), while a study of raw material categories was published by Sifogeorgaki et al (2023).…”

“…Gentle sheetwash and illuviation of the deposits could also result in this chitonic c/f distribution as well as the fine laminaes observed, although the rockshelter is currently well-protected from running water. The water observed in the higher moisture part of the sequence is not the result of sheetwash but rather originates from the rockshelter wall (Reidsma Sifogeorgaki & Dusseldorp, 2022;Sifogeorgaki et al, 2020). The SDl subfacies are present throughout the sequence and are very strongly expressed in the uppermost micromorphological sample (UMH30).…”

“…The current study builds upon the recent stratigraphic and geoarchaeological studies (Reidsma et al, 2021;Sifogeorgaki, 2020, Sifogeorgaki et al, 2023Sifogeorgaki & Dusseldorp, 2022), to provide a holistic assessment of the different formation processes that affected the sequence over the last 70,000 years. Specifically, we aim to address the following questions:…”