**Marine Reservoir Corrections: An overview**

Radiocarbon samples which
obtain their carbon from a different source (or reservoir) than atmospheric
carbon may yield an apparent age called a reservoir age. The Ocean has a reservoir
age of about 402
radiocarbon years (see Stuiver et al. 1986). This apparent age is caused both
by the delay in
exchange rates between atmospheric CO_{2} and ocean bicarbonate, and
the dilution effect caused by the mixing of surface waters with upwelled deep
waters. The reservoir age is incorporated
in the modelled marine curve of Stuiver et al. (1998).

Regionally, the ^{14}C of the ocean surface deviates from this modelled
marine curve due to variations in upwelling, ocean currents, and inter-hemispheric
atmospheric ^{14}C. Therefore,
when dating marine shells it is essential to know the
difference (ΔR) between the modelled radiocarbon age of surface water and
the known ^{14}C age of surface water at that time represented by the
marine shell sample. The
ΔR for a specific location (s) can be calculated from known age shells,
collected prior to atmospheric bomb testing using the formulae:

**Rs(t) – Rg(t) =
ΔR(s)
**

Where Rs(t) is the ^{14}C age of known-age sample and Rg(t) is the ^{14}C age of the model
mixed ocean layer for the calendar year (AD) of the known-age sample. The
ΔR standard error is calculated by the formulae:

More information on suitable shellfish for radiocarbon dating can be found here.

**References**

Stuiver M, Reimer PL, Braziunas TF, 1998. High-precision radiocarbon age calibration for terrestrial
and marine samples. *Radiocarbon,* 40(3): 1127-1154.

Stuiver M, Pearson GW, Braziunas TF, 1986. Radiocarbon Age Calibration of Marine Samples Back to
9000 cal yr BP. *Radiocarbon,* 28(2B): 980-1021.