Radiocarbon Dating Daniel De Schepper NCSS

Conception 1946 suggests that 14 C exists in living matter Confirmed a year later 1949 found that several trees contained roughly the same amount of activity due to 14 C 1960 won Nobel prize Willard Libby

Atmospheric neutron intensity and 14 C production 14 N + 1 n 14 C + 1 H CO 2 undergoes rapid equilibrium in the atmosphere

Assumptions 14 C production is constant The biosphere and atmosphere have roughly the same 14 C concentration After death there is no 14 C exchange and it is only affected by radioactive decay

Some Deviations Glacial effects Human activity Variations in natural production rate

Glacial effects CO 2 solubility is temperature dependant

Human activity Fossil fuel (Suess) effect and bomb effect

Variations in production rate Major cause of Suess wiggles

The need for calibration –Dendrochronology X-axis spans 2000 calendar years Y-axis is in radiocarbon age (BP) where 0 BP = 1950 AD

Sample Preparation Unearth sample Physical separation Treat with acid Convert carbon to CO 2 via combustion Remove impurities (ie nitrogen oxides, sulfur, products of incomplete combustion, and radon) Isolate carbon: 2 Mg + CO 2 MgO + C Limit exposure to air

Accelerator Mass Spectrometer Upper age limit 40,000 years Lower age limit 200 years

Archaeology 3100 to 4000 BC* 1423 to 1445 AD* 1260 to 1390 AD* * Radiocarbon date

Conclusions There are errors in radiocarbon dating due to assumptions this calls for calibration With this radiocarbon dating can be used to determine the age of a given sample Though variation still persists