REQUEST TO CONDUCT CARBON-14 AND CARBONATE DATING ON THREE OES BEADS

PGS Heritage (Pty) Ltd (PGS) was appointed by the Nkomati Anthracite Mine to manage the Phase 2 archaeological mitigation work required for the mitigation of several identified archaeological sites and to investigate features that may be graves. The planned expansion of mining activities in the area known as “Block L” will affect these archaeological sites and features.

PGS obtained an excavation permit from the SAHRA (Case ID: 18339) to undertake archaeological mitigation, test excavations, and ground penetrating radar scans to extensively excavate the archaeological sites and features and to collect representative samples of the archaeological material for analysis to determine the temporal localisation, cultural affiliation, and possible social structure and layout of the settlements. The mitigation work must also identify unmarked burials and ensure, as far as possible, that no unmarked burials are left in the area after the completion of the mitigation work.

The purpose of dating the three OES beads that have been selected were located near a grave and could potentially give a relative date for when the individual was buried.

1.2 Background
Carbon dating is a widely practised method for determining the age of archaeological sites around the world. It can accurately determine the age of a site or artefact up to approximately 66 000 years old. It is based on the premise that living organisms absorb C14 during their lifetime. Once these organisms die, the C14 slowly decays into other atoms over time. As a result, we can determine the time period in which an organism has died by counting the remaining C14 (Koppes and Lerner 2024). Once the age has been determined the date is then calibrated according to the atmospheric conditions in the area that the samples were taken.


1.3 Analysis methodology
For the pretreatment of the Ostrich eggshell bead, it goes through an acid etch. This is where the material is first washed with deionised water. This removes any organic sediments and debris. The sample will then be crushed and repeatedly subjected to HCl etches to eliminate secondary carbonate components (BETA Analytics 2022)

After pretreatment, the sample is burnt to turn it into graphite. This will be placed in the accelerated mass spectrometer. The best approach to dating ostrich egg shells is to try and date both the carbonate within the shell structure and the organic carbon within the shell structure. Since the organics are derived from the food and the carbonate is derived possibly from old carbon ingestion, the result may have two different sources of age-error. When the two dates agree, you have good credibility in age. If they do not agree, you will be left to make the judgment of which is more correct.
When analyzing this kind of sample the analysis will result in two sample charges, with two reported dates, one date on the organic fraction and one on the inorganic fraction. The results are then analysed and calibrated. The analysis will take place at the BETA Analytics Laboratory in America.