There are three methods used in determining regional differences in marine radiocarbon reservoir effect, as listed by Sean Ulm in a report dated December 2006: Terrestrial and marine samples cannot be compared or associated without accounting for the marine radiocarbon reservoir effect.Correction factors for different oceans in the world are found in an online database, the Marine Reservoir Correction Database, funded in part by the Institute for Aegean Prehistory.
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.
However, carbon 14 content is not the same at the surface mixing layers and that in the deep ocean; hence, not all marine organisms have the same radiocarbon content.
These carbon 14 atoms then instantaneously react with oxygen present in the atmosphere to form carbon dioxide.
The carbon dioxide formed with carbon 14 is indistinguishable from the carbon dioxide with the other carbon isotopes; hence the pathway of carbon 14 into the ocean, plants, and other living organisms is the same as that of carbon 12 and carbon 13.
Note: A negative Delta-R will make the date older (typically presuming freshwater dilution from the global marine average).
Sample reports below show the difference between a radiocarbon date of 1000 /-30 BP with a Delta R of 0 /-0 (i.e.
It is also assumed that there is equilibrium between carbon 14 formation and its decay, thus there is a constant level of carbon 14 in the atmosphere at any given time in the past up to the present.
The assumptions, however, do not paint the real picture.
The basis of radiocarbon dating includes the assumption that there is a constant level of carbon 14 in the atmosphere and therefore in all living organisms through equilibrium.