Calibration curves for the radiocarbon method -- Page 9 of 12

Working with Calibration or Correction Curves
Page 9 of 12

Using the findings of tree ring research, it's possible to "adjust" radiocarbon determined dates to correct for variations in atmospheric C-14. The "Correction" Curves on the right are taken from the work of reseachers M. Stuiver and B. Becker and are valid back to about 4500 years BP. Click each little button on the right of the curves to see the variation in atmospheric C-14 over time. Note that at times when the correction curve is below the line representing the expected amount of C-14 in the atmosphere--the diagonal red line, the amount of C-14 was more than normal and the corresponding corrected dates will need to be increased.

You can now use these curves to "correct" a measured radiocarbon date. Move the GREEN DOT directly on top of the black line of the "correction" curve to convert from Radiocarbon ages on the left vertical axis to "corrected" ages on the top horizontal axis. For example, in the 400 to 1000 BP age-range, a radiocarbon age of 800 years BP has a corrected age of only 680 years BP.

Correction Curves

0–400 BP
400–1000 BP
900–1500 BP
1400–2000 BP
1900–2500 BP
2400–3000 BP
2900–3500 BP
3400–4000 BP
3900–4500 BP

1.	Use the appropriate correction curve to convert a Radiocarbon measured age of 1450 BP to the corrected BP age.
	1500 BP 1450 BP 1400 BP 1350 BP 1300 BP
2.	Use the appropriate correction curve to convert a Radiocarbon determined age of 2700 BP to the corrected BP age.
	2700 BP 2750 BP 2800 BP 2850 BP unknown
3.	The modern-day burning of fossil fuels (coal, oil and natural gas) is diluting the relative amount of C-14 in the atmosphere by releasing large amounts of C-12. Unless a correction curve is established, future age determinations for artifacts of our time will appear to be:
	older than they should be younger than they should be of the correct age no one can say it will not be possible to construct a correction curve.
4.	Examine the correction curve at the Radiocarbon time of 2225 years BP. Note the dip in the curve so that more than one corrected date corresponds to the 2225 date. A reasearcher should:
	use the lowest corrected date use the largest corrected date use the average of high and low values seek other information to verify the most likely date throw out the data.