Define radiochemical dating
A radiocarbon measurement is termed a conventional radiocarbon age (CRA).
The CRA conventions include (a) usage of the Libby half-life, (b) usage of Oxalic Acid I or II or any appropriate secondary standard as the modern radiocarbon standard, (c) correction for sample isotopic fractionation to a normalized or base value of -25.0 per mille relative to the ratio of carbon 12/carbon 13 in the carbonate standard VPDB – Cretaceous belemnite formation at Peedee in South Carolina, (d) zero BP (Before Present) is defined as AD 1950, and (e) the assumption that global radiocarbon levels are constant.
These values have been derived through statistical means.Over the years, other secondary radiocarbon standards have been made.Radiocarbon activity of materials in the background is also determined to remove its contribution from results obtained during a sample analysis.Background radiocarbon activity is measured, and the values obtained are deducted from the sample’s radiocarbon dating results.
Background samples analyzed are usually geological in origin of infinite age such as coal, lignite, and limestone.Over the years, carbon 14 dating has also found applications in geology, hydrology, geophysics, atmospheric science, oceanography, paleoclimatology and even biomedicine.