Radiocarbon ages of samples formed in the ocean, such as shells, fish, marine mammals etc., are generally several hundred years older than their terrestrial counterparts. This apparent age difference is due to the large carbon reservoir of the oceans. A correction is necessary in order to compare marine and terrestrial samples, but because of complexities in ocean circulation the actual correction varies with location. This regional difference from the average global marine reservoir correction is designated ΔR (Stuiver and Braziunas, 1993) As a first approximation, ΔR is assumed to be a constant for a given region and is calculated from the difference in 14C years of known age marine samples and the marine model age for that calendar age. The marine reservoir correction database presented here is intended for use with radiocarbon calibration programs such as CALIB ( Stuiver and Reimer, 1993) or OxCal ( Bronk Ramsey 1995) using the Marine20 calibration curve.
ΔR values were calculated from the difference in the 14C age of known-age, pre-nuclear marine samples and the Marine20 calibration curve. Samples from depths greater than 75 m are not included in the database, because the marine model ages in the Marine20 calibration curve are only valid for the surface mixed layer. In cases where the 14C measurements were originally reported as δ14C, Δ14C, or pMC values, we recalculated the conventional 14C age, correcting for isotopic fractionation if that had not been done previously.
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