CALIB Manual - Chapter 5

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Conventional radiocarbon ages have been corrected for isotope fractionation by normalizing to = -25‰ PDB or VPDB. CALIB no longer supports the correction for isotope fractionation within the program for the following reason: The d¹³C correction depends on whether the original measurement was a 14C/12C ratio (all radiometric and some AMS) or a 14C/13C ratio (some AMS systems). An Excel spreadsheet with the formulas for both types of systems is given here. If you don't know which type of measurement was done it is better to contact the laboratory which supplied the radiocarbon date.

MS Excel spreadsheet for d ¹³C corrections

Table 1

Table 1
Suggested mean d13C values for various materials.* Adapted from Stuiver and Polach, 1977 and Polach, 1976.
Material d¹³C per mil
relative to PDB standard
Marine HCO₃^-1 1 ± 1
Marine CO₃^-2 0 ± 2
Soil CO₃^-2 and Secondary Bone CO₃^-2 -5 ± 2
Speleothems -8 ± 2
Atmospheric CO₂ -9 ± 2
Bone Apatite and Original CO₃^-2 -10 ± 2
Grains, Seeds, Maize, Millet -10 ± 2
Marine Plants (Submerged) -12 ± 2
Fresh Water HCO₃^-1 -12 ± 2
Grasses Arid Zone, Sedges, Papyrus -13 ± 2
Straw Flax -14 ± 2
Marine Organisms -15 ± 2
Fresh Water Plants (Submerged) -16 ± 4
Succulents (Cactus, Pineapple, etc.) -17 ± 2
Bone Collagen, Wood Cellulose -20 ± 2
Grains (Wheat, Oats, Rice, etc.) -23 ± 2
Graphite, Coal -23 ± 2
Fossil Wood, Charcoal -24 ± 2
Recent Wood, Charcoal -25 ± 2
Tree Leaves, Wheat, etc. Straw -27 ± 2
Peat, Humus -27 ± 3

Table 1
Suggested mean d13C values for various materials.* Adapted from Stuiver and Polach, 1977 and Polach, 1976.
Material	d¹³C per mil relative to PDB standard
Marine HCO₃^-1	1 ± 1
Marine CO₃^-2	0 ± 2
Soil CO₃^-2 and Secondary Bone CO₃^-2	-5 ± 2
Speleothems	-8 ± 2
Atmospheric CO₂	-9 ± 2
Bone Apatite and Original CO₃^-2	-10 ± 2
Grains, Seeds, Maize, Millet	-10 ± 2
Marine Plants (Submerged)	-12 ± 2
Fresh Water HCO₃^-1	-12 ± 2
Grasses Arid Zone, Sedges, Papyrus	-13 ± 2
Straw Flax	-14 ± 2
Marine Organisms	-15 ± 2
Fresh Water Plants (Submerged)	-16 ± 4
Succulents (Cactus, Pineapple, etc.)	-17 ± 2
Bone Collagen, Wood Cellulose	-20 ± 2
Grains (Wheat, Oats, Rice, etc.)	-23 ± 2
Graphite, Coal	-23 ± 2
Fossil Wood, Charcoal	-24 ± 2
Recent Wood, Charcoal	-25 ± 2
Tree Leaves, Wheat, etc. Straw	-27 ± 2
Peat, Humus	-27 ± 3

* Please note: this table has not been revised since the 1977 publication. Many d13C measurements on a wide variety of materials have been made since this table was published. For additional estimates, see also Fritz and Fontes, 1980. For a review of the factors affecting d13C in plants and animals see Tieszen and Boutton, 1989 or Fry and Sherr, 1984. An extensive listing of d13C measurements for marine algae and cyanobacteria is given in Kerby and Raven, 1985.

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