K-Ar Rb-Sr 238U- 206Pb 235U- 207Pb Pb-Pb 232Th-208Pb FT All Methods Score = 0 4 3 0 0 1 1 2 1 0 < Score < 0.50 3 1 3 2 3 1 1 23 0.50 ≤ Score < 1 1 1 1 1 0 0 0 10 Score = 1 9 5 5 6 5 2 1 1 Total Count 17 10 9 9 9 4 4 34 Average Score 0.63 0.61 0.73 0.80 0.62 0.60 0.33 0.39 % Concordant (Score = 1) 53% 50% 56% 67% 56% 50% 25% 2.9% Table 4. The distribution of concordance scores for each method from the “Three Methods Comparisons” dataset. Also includes the average score and the percentage of concordant records. Figure 4. Scatterplot of radioisotope age determinations for Record #77. Radioisotope ages are plotted against the present half-lives of the parent radioisotopes, with any specified error bars shown. The color of each data point represents the atomic weight of each parent isotope, as given by the legend on the right-hand side of each plot. Diamond-shaped data points represent α-decay, circle-shaped data points represent β-decay, and plus-shaped points represent nuclear fission. BEACHY, KINARD AND GARNER How often do radioisotope ages agree? 2023 ICC 393
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