Some of the most widely dated fossil groups are the marine carbonates including foraminifera, mollusks, pteropods, and corals.
This discovery meant that there are three naturally occurring isotopes of carbon: Whereas carbon-12 and carbon-13 are stable isotopes, carbon-14 is unstable or radioactive.
Carbon-14 is produced in the upper atmosphere when cosmic rays bombard nitrogen atoms.
These coastal radiocarbon reservoir age data don't satisfy our need for the open ocean because of their limited geographic distribution and they are often influenced by organism diets, sediment pore waters or river mixing among other factors.
The paleoceanography community in particular needs a reliable standard reference for estimating the surface ocean radiocarbon reservoir age at any point in the World's oceans.
During the lifetime of an organism, the amount of c14 in the tissues remains at an equilibrium since the loss (through radioactive decay) is balanced by the gain (through uptake via photosynthesis or consumption of organically fixed carbon).
However, when the organism dies, the amount of c14 declines such that the longer the time since death the lower the levels of c14 in organic tissue.The surface ocean radiocarbon reservoir age varies geographically due to the combined influences of varying air-sea isotopic exchange rates and mixing with older, radiocarbon depleted, deep waters. We recognize the important contribution made by Butzin, Prange and Lohmann in their seminal paper on the radiocarbon reservoir age for the preanthropogenic and glacial world simulations (Butzin et al., 2005). However, there is only a handful of pre-anthropogenic measurements of reservoir ages uncontaminated by fossil fuel burning or thermonuclear bomb contamination for the open ocean environments, and there is little prospect for adding significantly to this data base. There are many radiocarbon reservoir age measurements from coastal environments where mollusks and other museum specimens have known collection dates. Radiocarbon samples which obtain their carbon from a different source (or reservoir) than atmospheric carbon may yield an apparent age called a reservoir age.