REQUEST TO CONDUCT CARBON-14 DATING ON TEN CHARCOAL SAMPLES

1.1 Introduction
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 ten charcoal samples and three OES beads for the Nkomati site is to establish a reasonable sequence of occupation of the different sites in the area. The charcoal is derived from wood that had been burnt and discarded in the kraal and midden. The 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
Before the charcoal sample is subjected to the dating process, it is pretreated to remove contaminants by using the Acid/Alkali/Acid method. This is done by gently crushing the sample, which is then dispersed in de-ionised water. It is then washed with hot HCL acid to eliminate carbonates. The sample is then further washed with NaOH to remove any secondary organic acids. The sample is then rinsed with acid in order to neutralise the solution and is then dried (BETA Analytics 2022). This treatment may be applied numerous times depending on the sample that has been submitted.


After pretreatment, the sample is burnt to turn it into graphite. This will be placed in the accelerated mass spectrometer. The results are then analysed and calibrated. The analysis will take place at the BETA Analytics Laboratory in America.
 
2 BIBLIOGRAPHY
BETA ANALYTICS (2022). Beta Analytic Standard Pretreatment Protocols.
https://www.radiocarbon.com/pretreatment-carbon-dating.htm
KOPPES, S & LERNER, L (2024) Carbon-14 dating explained. UChicargo News
https://news.uchicago.edu/explainer/what-is-carbon-14-dating