DISTANCE [cm] is the distance from rim. Distance from rim is measured along the growth axis. 'Percentage of corrected modern carbon'is the fraction of 14C relative to the "modern" value (1950 A.D.), corrected for fractionation using the 13C/12C measurements. D14C values were calculated from the corrected percentage of modern carbon using estimates of the true age of the samples taken from the U-Th datings. This age correction is very small (<1% in all samples) so uncertainties introduced by incorrect age estimates are negligible.