Dating annual tree growth rings of known historical age has demonstrated that in the past there have been short term variations in atmospheric C levels.Tree ring dating has been used to construct a probabilistic calibration curve extending back to 11857 calendar years BP (see figure below).Careful sample preparation by Strata Data is matched by the world class analysis by Beta Analytic Inc.
Suitable for dating sediments up to c.45Ka old as long as they contain suitable biogenic material (molluscs, microfossils, wood).
C dating have traditionally been quoted in “conventional radiocarbon years”, typically in years BP (before present) where the “present” is 1950.
The initial assumption that the concentration of atmospheric C has been constant as measured in 1950 has been shown to be incorrect.
This difference which is called the reservoir age is caused both by the delay in exchange rates between atmospheric CO and oceanic bicarbonate, and the dilution effect caused by mixing surface waters with upwelling deep waters which are very old.
A reservoir correction factor must therefore be applied to conventional radiocarbon dates based on the remains of marine organisms.