CARBON 14 Technique

The collision of cosmic-ray-produced thermal neutrons with nitrogen nuclei generates 14C by a reaction in the upper atmosphere. Rapid oxidation to carbon dioxide and global homogenization within 2-3 years introduces the resultant 14CO2 into the carbon cycle, where the radioactive CO2 is taken up in photosynthesis or precipitated as carbonate mineral. 14C decays by beta emission with a half-life of approximately 5700 years giving a useful age range of approximately 50,000 (approximately 80-100,000 years with AMS) b.p. Several sample preparatory labs for 14C exist within the USGS, as well as services of commercial labs. Working arrangements with Lawrence Livermore National Labs AMS facility (or others) provide the isotopic data from prepared samples. Individuals must make their own arrangements for obtaining C-14 data, but may find the following contact people helpful.

| Capabilities | | Geochronology, Geochemistry, and Tracer Studies  | | Geochronology  |

URL http://geology.cr.usgs.gov/capabilities/gronemtrac/geochron/carbon/tech.html