Burial dating in archaeology using 10Be and 26Al in-situ produced cosmogenic radioisotopes

Abstract

Dating sediment associated with archaeological artefacts and hominid fossils over the Plio-Pleistocene is difficult due to the limited range of radiocarbon, U-series and OSL techniques, with magnetostratigraphy being the only dating tool to offer chronological constraints. Recently a new innovative technique - in-situ cosmogenic burial dating – can provide burial ages from 0.5 to 5 Ma with errors of about 10%-15%. Galactic cosmic ray particles which interact with bedrock surfaces and boulders on the Earth’s surface result in producing a host of long-lived cosmogenic radionuclides (eg 10Be and 26Al). If we know the production rate of these radioisotopes, their half-life and can measure their minute concentration via AMS, we can estimate the time the bedrock or boulder has been exposed. If this material after initial dosing is transported to depths a few meters below the surface, production will cease, and decay will reduce their concentrations. The change in concentration is a measure of the burial age. If burial depth is insufficient, post-burial production by deep penetrating muons can be estimated to correct the burial age. The method has been successfully applied at key sites of hominid evolution. Details of the technique will be presented with examples of burial dating hominid cave deposit. © ANSTO