Sample reports below show the difference between a radiocarbon date of 1000 /-30 BP with a Delta R of 0 /-0 (i.e.
with just the global marine reservoir correction) and a 1000 /-30BP radiocarbon date with a Delta R of 222 /-35 and the global marine reservoir correction included.
Terrestrial organisms like trees primarily get carbon 14 from atmospheric carbon dioxide but marine organisms do not.
Samples from marine organisms like shells, whales, and seals appear much older.
Depending on the age of the marine carbonate, a 200- to 500-year correction (i.e.
global marine reservoir correction) is applied automatically for all marine carbonates.
Another characteristic of carbon 14 is that it is continually being formed in the upper atmosphere as a product of the reaction between neutrons produced by cosmic rays and nitrogen atoms.
These carbon 14 atoms then instantaneously react with oxygen present in the atmosphere to form carbon dioxide.
There are several factors that need to be considered because they affect the global concentration of carbon 14 and therefore that of any given sample for radiocarbon dating.Freshwater systems running through limestone or fed by old water from springs can lead to falsely old ages in carbonate AMS dates.The dissolved inorganic carbon (DIC) used by the individuals to form their shells or in the precipitation of carbonate concretions will be older than the time of formation due to old DIC from the limestone.This is how terrestrial organisms take in carbon 14 in their systems.Marine organisms and those who consume them take in carbon 14 from the exchange process of carbon 14 (in the form of carbon dioxide) in the atmosphere and the ocean or any body of water.The degree of equilibration of carbon dioxide in deep water remains unknown.