Carbon cosmogenic isotopes

Authigenic Deposits. Carbon Cycle. Cenozoic Climate - Oxygen Isotope Evidence. Cenozoic Oceans - Carbon Cycle Models. Cosmogenic Isotopes. Mid-Ocean Ridge Geochemistry and Petrology. Rare Earth Elements and their Isotopes in the Ocean. River Inputs. Stable Carbon Isotope Variations in the Ocean. Uranium-Thorium Series Isotopes in Ocean Profiles. 

Radiocarbon is a cosmogenic isotope, produced in the upper atmosphere. It is incorporated into almost all living organisms, but once they die and stop taking up carbon from the atmosphere, the radiocarbon content decays away with a half-life of about 5,730 years. 

Carbon-14 ( " C, half-life = 5730 yr) is also formed cosmogenically by interactions with atmospheric nitrogen. This quickly gets mixed with the stable carbon pool and background concentrations are typically about 227 Bq kg stable carbon. Increasing fossil-fuel emissions, which are depleted in " C are diluting this carbon isotope so that the ratio of " C to is decreasing over time in the atmosphere. 

---