Accurate radiocarbon dating of archaeological ash using pyrogenic aragonite

Obtaining accurate age determinations from minerals in archaeological ash is a major unsolved issue in radiocarbon (¹⁴C) dating. This is because the original¹⁴C content of calcite, the main component of ash, is altered by isotopic exchange. Pyrogenic aragonite, another mineral phase recently discovered in ash, might preserve its¹⁴C signature through time. Using a new method based on density separation and step combustion, we were able to isolate and date aragonitic ash from an archaeological destruction horizon of known age. Here we show that the¹⁴C age of aragonite matches the age of the destruction horizon. Our results demonstrate that pyrogenic aragonite is a short-lived material suitable for¹⁴C dating and directly related to human activities involving the use of fire, thus bearing major implications for the establishment of absolute chronologies for the past 50,000 yr.