Influence of different extraction methods on prehistoric phytolith radiocarbon dating

The use of carbon in phytoliths for radiocarbon dating is recognized as a non-traditional radiocarbon dating method. Its reliability in constructing the chronological sequence of archaeological sites has been questioned in recent studies. The influence of different phytolith extraction methods on dating results has been considered as the potential cause of distortion in phytolith dating. However, few studies have focused on comparing different phytolith extraction methods for measuring radiocarbon. In this study, we applied two methods, a conventional method utilizing pre-treatment with H2O2 and HCl and an improved method, to extract phytoliths from the cultural layers of several archaeological sites in China. The results showed that phytolith dates acquired using the conventional method were approximately 3000–10,000 years older than those found using the improved method. This large distortion in phytolith dates was likely caused by clays within the phytoliths and organic materials on the surfaces of phytoliths, which were not completely removed. The phytolith dates acquired using the improved method were consistent with the ages estimated from the typological sequence, indicating that our soil phytolith dates were not markedly biased by the older carbon absorbed from the soil.